Trane CDHF, CDHG, CVHE, CVHF, CVHG, Drives, Starters Engineering Bulletin

CTV-PRB004.book Page 1 Sunday, December 18, 2011 6:39 PM

Engineering Bulletin

Starters, Drives, and Electrical Components for CenTraVac™ Chillers

Models: CVHE, CVHF, CVHG, CDHF, CDHG

SAFETY WARNING

Only qualified personnel should install and service the equipment. The installation, starting up, and servicing of heating, ventilating, and air-conditioning equipment can be hazardous and requires specific knowledge and training. Improperly installed, adjusted or altered equipment by an unqualified person could result in death or serious injury. When working on the equipment, observe all precautions in the literature and on the tags, stickers, and labels that are attached to the equipment.

December 2011

CTV-PRB004-EN


Warnings, Cautions and Notices

Warnings, Cautions and Notices.

Note that warnings, cautions and notices appear at appropriate intervals throughout this manual.Warnings are provided to alert installing contractors to potential hazards that could result in death or personal injury. Cautions are designed to alert personnel to hazardous situations that could result in personal injury, while notices indicate a situation that could result in equipment or property-damage-only accidents.

Your personal safety and the proper operation of this machine depend upon the strict observance of these precautions.

Read this manual thoroughly before operating or servicing this unit.

ATTENTION: Warnings, Cautions and Notices appear at appropriate sections throughout this literature. Read these carefully:

WARNING

CAUTION

s

NOTICE:

Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury.

Indicates a potentially hazardous situation which, if not avoided, could result in minor or moderate injury. It could also be used to alert against unsafe practices.

Indicates a situation that could result in equipment or property-damage only accidents.

Important

Environmental Concerns!

Scientific research has shown that certain man-made chemicals can affect the earth’s naturally occurring stratospheric ozone layer when released to the atmosphere. In particular, several of the identified chemicals that may affect the ozone layer are refrigerants that contain Chlorine, Fluorine and Carbon (CFCs) and those containing Hydrogen, Chlorine, Fluorine and Carbon (HCFCs). Not all refrigerants containing these compounds have the same potential impact to the environment.

Trane advocates the responsible handling of all refrigerants-including industry replacements for

CFCs such as HCFCs and HFCs.

Responsible Refrigerant Practices!

Trane believes that responsible refrigerant practices are important to the environment, our customers, and the air conditioning industry. All technicians who handle refrigerants must be certified. The Federal Clean Air Act (Section 608) sets forth the requirements for handling, reclaiming, recovering and recycling of certain refrigerants and the equipment that is used in these service procedures. In addition, some states or municipalities may have additional requirements that must also be adhered to for responsible management of refrigerants. Know the applicable laws and follow them.

WARNING

Proper Field Wiring and Grounding Required!

All field wiring MUST be performed by qualified personnel. Improperly installed and grounded field wiring poses FIRE and ELECTROCUTION hazards. To avoid these hazards, you MUST follow requirements for field wiring installation and grounding as described in NEC and your local/state electrical codes. Failure to follow code could result in death or serious injury.

© 2011 Trane All rights reserved CTV-PRB004-EN


Warnings, Cautions and Notices

WARNING

Personal Protective Equipment (PPE) Required!

Installing/servicing this unit could result in exposure to electrical, mechanical and chemical hazards.

• Before installing/servicing this unit, technicians MUST put on all Personal Protective

Equipment (PPE) recommended for the work being undertaken. ALWAYS refer to appropriate

MSDS sheets and OSHA guidelines for proper PPE.

• When working with or around hazardous chemicals, ALWAYS refer to the appropriate MSDS sheets and OSHA guidelines for information on allowable personal exposure levels, proper respiratory protection and handling recommendations.

• If there is a risk of arc or flash, technicians MUST put on all Personal Protective Equipment

(PPE) in accordance with NFPA 70E or other country-specific requirements for arc flash protection, PRIOR to servicing the unit.

Failure to follow recommendations could result in death or serious injury.

CTV-PRB004-EN

Trademarks

Adaptive Frequency, CenTraVac, Duplex,TOPSS,Tracer AdaptiView,Tracer Summit,Trane, and the

Trane logo are trademarks or registered trademarks of Trane in the United States and other countries.Trane is a business of Ingersoll Rand. All trademarks referenced in this document are the trademarks of their respective owners.

Cutler-Hammer is a registered trademark of Eaton Corporation.

3


Table of Contents

Introduction

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

About Starters

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

What a Starter Does . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Motor Types and Voltage Classes

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Voltage Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Chiller Selection and Electrical Specification

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Standard Components of Trane Starters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Chiller Selection Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Motor Protection

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Low-Voltage Starter Types

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Low Voltage—Wye-Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Wye-Delta Starters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Low Voltage—Solid-State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Solid-State Starters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Low Voltage—Unit-Mounted Adaptive Frequency Drive . . . . . . . . . . . . . . . . 25

Low Voltage—Remote-Mounted Adaptive Frequency Drive . . . . . . . . . . . . . 28

Medium-Voltage Starter Types (2,300–6,600 Volts)

. . . . . . . . . . . . . . . . . . . . . . . 31

Medium Voltage—Across-the-Line (2.3–6.6 kV) . . . . . . . . . . . . . . . . . . . . . . . 32

Across-the-Line Starter (2,300–6,600 volts) . . . . . . . . . . . . . . . . . . . . . . . . 32

Medium Voltage—Primary Reactor (2.3–6.6 kV) . . . . . . . . . . . . . . . . . . . . . . . 35

Primary Reactor Starter (2,300–6,600 volts) . . . . . . . . . . . . . . . . . . . . . . . 35

Medium Voltage—Autotransformer (2.3–6.6 kV) . . . . . . . . . . . . . . . . . . . . . . 38

Autotransformer Starter (2,300–6,600 volts) . . . . . . . . . . . . . . . . . . . . . . . 38

Unit-Mounted Starter Top Hat—NEC 2005 Code Requirement . . . . . . . . 40

Medium Voltage—Remote-Mounted Adaptive Frequency Drive . . . . . . . . . 42

Chiller Unit Control Features for the AFD . . . . . . . . . . . . . . . . . . . . . . . . . 43

Medium-Voltage Starter Types (10,000–13,800 Volts)

. . . . . . . . . . . . . . . . . . . . . 45

Medium Voltage—Across-the-Line (10–13.8 kV) . . . . . . . . . . . . . . . . . . . . . . . 45

Across-the-Line Starter (10,000–13,800 volts) . . . . . . . . . . . . . . . . . . . . . . 45

Medium Voltage—Primary Reactor (10–13.8 kV) . . . . . . . . . . . . . . . . . . . . . . 47

Primary Reactor Starter (10,000–13,800 volts) . . . . . . . . . . . . . . . . . . . . . 47

Medium Voltage—Autotransformer (10–13.8 kV) . . . . . . . . . . . . . . . . . . . . . . 48

Autotransformer Starter (10,000–13,800 volts) . . . . . . . . . . . . . . . . . . . . . 48

Electrical System—Ratings

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Electrical System—Design Guidelines

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4 CTV-PRB004-EN


Disconnect Means . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Short-Circuit Interruption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Power Circuit Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Electrical System–Power Wire Sizing

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Starter Options

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Multiple Starter Lineups (2,300–6,600 volts) . . . . . . . . . . . . . . . . . . . . . . . 61

Industrial-Grade Starters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Glossary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

CTV-PRB004-EN 5


Introduction

This document explains key electrical concepts and starter product information relating toTrane ® water chillers. Topics include voltage classes, motors, motor protection, starter types, variablefrequency drives, wire sizing, power factor correction, and electrical term definitions.

Information in this document changes frequently. To make sure you are viewing the most recent version, be sure to download the latest copy available on e-Library.

Dimensional data

Job specific submittals are always the best source of dimensional data. General starter dimensions are shown with the descriptions of each starter type in this document.

Wiring information

The best source for additional information is the Installation, Operation, and Maintenance manual shipped with the chiller. Field connection diagrams are also available on the website.

All unit-mounted starters are designed for top-entry line power only. Remote starters are typically designed for top-entry line power and a bottom exit for load wires. The medium-voltage starter submittals show conduit space for alternate wiring options. Additional wiring options may be available.

For your convenience, power wire sizing charts for various voltages and conduit combinations are provided.

Fuse and circuit breaker sizing

Proper sizing of fuses and circuit breakers upstream of the starter is the responsibility of the customer or the electrical engineer. Disconnects and circuit breakers are options that can be installed within theTrane ® starters. WhatTrane would install may not necessarily satisfy UL, NEC, or local code requirements for installation of overcurrent devices.

Important: Trane, in presenting electrical information and system design and application concepts, assumes no responsibility for the performance or desirability of any resulting system design. Design of the HVAC and related electrical system is the prerogative and responsibility of the engineering professional.Trane has a policy of continuous product and product information improvement and reserves the right to change design and specifications without notice. Consult the chiller submittal for the most up-to-date information as applied to the specific chiller under consideration.

6 CTV-PRB004-EN


About Starters

What a Starter Does

Electric, centrifugal, water-cooled chillers use relatively large induction motors to drive the compressors.These motors use a control device to connect to and disconnect from the electrical power source.These control devices are referred to as combination controllers or, most commonly, as motor starters. Variable-frequency drives or Adaptive Frequency™ Drives (AFDs) also serve as motor starters, but their capabilities extend beyond starting and stopping the motor.

There are three main functions of the motor starter.The first function is to serve as the link between the chiller’s motor and the electrical distribution system. It is used during the starting and stopping sequence.

Starting an induction motor from standstill causes a large electrical current draw for a few seconds.

The extra current is used to develop the required torque to get the compressor motor running at full speed. The initial rush of current decreases as the compressor motor ramps up to full speed, and is commonly referred to as inrush current.

The second function of the starter is to keep the initial current inrush below a specified level.Third, the starter communicates with the unit controller to coordinate motor protection.

Starters can be as simple or as complex as necessary to meet various engineering specifications and/or customer needs. A variable-speed drive can provide starter functions, among other things

(see “Low Voltage—Unit-Mounted Adaptive Frequency Drive,” p. 25 and “Medium Voltage—

Remote-Mounted Adaptive Frequency Drive,” p. 42 ). It will be classified as a starter type for the purposes of this document.

Several voltage classes and starter types are available as indicated on the chart below. Each one is described in greater detail in this document.

Table 1.

Trane CenTraVac chiller starter choices

Medium Voltage

(10–13.8 kV)

Remote-Mounted

Across-the-Line

Up to 94 amps

Isolation switch, power fuses standard

Low Voltage (208–600 V)

Remote-Mounted Unit-Mounted

Medium Voltage (2,300–6,600 V)

Remote-Mounted Unit-Mounted

Wye-Delta

Up to 1,700 amps

Wye-Delta

Up to 1,316 amps

(Up to 1,120 amps with disconnect/circuit breaker option)

Across-the-Line

Up to 360 amps


Solid-State

(Up to 1,120 amps with disconnect or circuit breaker required)

Solid-State

(Up to 1,120 amps with disconnect or circuit breaker required)

Primary Reactor

Up to 360 amps


Adaptive Frequency

Drive

V

Up to

amps

1,120


Drive

Up to 1,210 amps

Circuit breaker standard

460–480 V

Autotransformer

Up to 360 amps



Drive

amps


Across-the-Line

Up to 288 amps


Primary Reactor

Up to 205 amps


Autotransformer

Up to 205 amps


Primary Reactor

Up to 94 amps


Autotransformer

Up to 94 amps


CTV-PRB004-EN 7


8

Motor Types and Voltage Classes

Voltage Classes

There are two primary voltage classes typically used in the water-cooled chiller industry: low and medium. For centrifugal chillers this is generally restricted to three-phase power only.

Low voltage ranges from 208 to 600 volts. Starters and frequency drives in this voltage range include sizes up to 1,700 amps.

Medium voltage has two main voltage groups. One ranging from 2,300 to 6,600 volts and the other ranging from 10,000 to 13,800 volts. Starters in this class have sizes up to 360 amps and 94 amps respectively.

For a given power (kW), the higher the voltage the lower the amperage. The voltage is typically established prior to creating the job plans and specifications.

Motors

A centrifugal motor is a relatively simple motor. Specifically, it is referred to as a three-phase, squirrel-cage, 3,600-rpm, alternating-current induction motor with two-pole construction.

The squirrel-cage motor consists of a fixed frame, or stator, carrying the stator windings and a rotating member called the rotor.

Figure 1 shows a cutaway of a typical low-voltage motor. The rotor is built by rigidly mounting steel laminations to the motor shaft.The motor winding consists of aluminum bars that are die-cast into slots in the rotor.The aluminum bars are connected at each end by a continuous ring.This skeleton of rotor bars with end rings looks like a squirrel cage and gives the motor its name.

Figure 1.

Low-voltage motor Figure 2.

Medium-voltage motor

Stator

Stator

Rotor shaft

Rotor shaft

In a three-phase motor, three windings on the stator connect to a motor terminal board, and ultimately to the power grid via the starter. When the polyphase alternating current flows through the stator winding it produces a rotating magnetic field.The resulting magnetic forces exerted on the rotor bars cause the rotor to spin in the direction of the stator field.The motor accelerates until a speed is reached corresponding to the slip necessary to overcome windage and friction losses.

This speed is referred to as the no-load speed.

Low-voltage motors typically have six motor terminals to electrically connect the motor in a wye

(star) or delta configuration. Most low-voltage motors are random-wound motors, but larger amperage higher horsepower motors are form wound for better heat dissipation. Connecting links can be used to convert the six motor electrical connections to three connections.

Medium-voltage motors (2,300–6,600 V) have three motor terminals.

Figure 2 shows a typical medium-voltage motor minus the rotor shaft. You can visually compare most low- and medium-

CTV-PRB004-EN


Motor Types and Voltage Classes voltage motors. Medium-voltage motors are always form wound and you can see that the insulation is thicker and the windings are more evenly spaced.

Figure 3.

Ceramic insulators on medium-voltage motor (10-13.8 kV)

Medium-voltage motors (10–13.8 kV) have the same design and construction attributes as other medium-voltage motors with some externally visible differences. Ceramic insulators and larger spacing of the motor terminals are commonly found on typical 10–13. kV medium-voltage motors.

Internally, these motors are form wound and structurally similar to other medium-voltage motors.

The ceramic insulators combined with the larger spacing between the motor terminals help prevent electrical arcing.

Higher voltage motors and starters are being used in large chiller plants where incoming line power makes 10–13.8 kV accessible. In some cases, higher voltage chillers allow for the elimination of electrical components with their associated space requirements and energy losses. In particular, chiller installations with on-site or dedicated power generation, such as district cooling, higher education, hospitals, industrials, and airports have opportunities for electrical distribution system simplification and energy savings.

Benefits of 10,000–13,800 volts include:

• No need for step-down transformer

• No transformer losses

• Higher uncorrected power factor

• Reduced electrical design and labor

• Reduced mechanical room space

Note: Motors and starters at 10,000–13,800 volts typically cost more, and the motor efficiency is lower than 2,300–6,600-volt motors.

Motors are available in specific power sizes, which are rated in kilowatts or horsepower. The

TOPSS™ computer software selection program selects the proper motor to meet the specific cooling duty of the application.

CTV-PRB004-EN 9


Chiller Selection and Electrical Specification

Standard Components of Trane Starters

• A 4 kVA control-power transformer (CPT) supports all of the chiller auxiliary power needs—

3 kVA control-power transformer supplied with AFDs.

• Primary and secondary current transformers (CTs) support the overload and momentary power loss protection functions of the unit controller.This allows amps per phase and percent amps to be displayed at the unit controller.

• Potential transformers (PTs) support motor protection functions such as under/overvoltage within the unit controller. This allows voltage per phase, kilowatts, and power factor to be displayed at the unit controller.

• Grounding provisions are standard.

• A terminal block for line power connection is standard. Load-side lugs are standard for remote starters.The lug sizes and configuration are shown on the submittal drawing.TheTrane

® AFD has a circuit breaker as standard. Medium-voltage starters have provisions for a bolted connection.

Chiller Selection Report

The following terms are found on a typical TOPSS product report. Review the example selection output report shown in Figure 4, p. 12 .

Electrical information

Usually the primary RLA (incoming line), compressor motor RLA, and kW of the chiller are used as nameplate values. In this section, we will review the typical electrical data presented on the selection report.

A. Motor size (kW).

The motor size is listed on the program report based on its output kW.The

output kW is the motor’s full, rated power capacity.There is an amperage draw associated with the motor size called full-load amps (FLA). FLA is the amperage the motor would draw if it were loaded to its full rated capacity, i.e. the motor size. The FLA is not available from the chiller selection program, but it can be obtained from motor data sheets upon request.

B. Primary power (kW).

The primary power is the power the chiller uses at its design cooling capacity. The primary power will always be less than or equal to the motor size.

C. Motor locked-rotor amps (LRA).

There is a specific locked-rotor amperage value associated with each specific motor. This is the current draw that would occur if the rotor shaft were instantaneously held stationary within a running motor. LRA is typically six to eight times the motor full-load amps (FLA). LRA is also used commonly in discussing different starter types and the inrush amperages associated with the motor start. For example, a wye-delta starter will typically draw approximately 33 percent of the motor LRA to start. A solid-state starter will draw approximately 45 percent of the motor LRA to start.

D. Primary rated-load amps (RLA [incoming line]).

The RLA is also commonly referred to as the selection RLA or unit RLA.This is the amperage that is drawn on the line side when the chiller is at full cooling capacity. Nameplate RLA (usually the same as primary RLA [incoming line]) is the key number used to size the starter, disconnects, and circuit breaker. Primary RLA (incoming line) is also the value used to determine the minimum circuit ampacity (MCA) for sizing conductors.

Primary RLA (incoming line) is always less than or equal to the motor full-load amps (FLA).

E. Compressor motor RLA.

This is the amperage between the motor and starter or AFD. If the unit is a starter, the compressor motor RLA will be almost identical to the primary RLA (incoming line). If the unit is an AFD, typically, the compressor motor RLA will be larger. This value is used to size the AFD.The primary RLA (incoming line) is lower due to the improved power factor of the

AFD.

10 CTV-PRB004-EN



F. Minimum circuit ampacity (MCA).

This term appears on the chiller nameplate and is used by the electrical engineer to determine the size and number of conductors needed to bring power to the starter.

MCA = 1.25 x (Primary RLA [incoming line])+

( 4000 volts motor

)

… with this number rounded up to the next whole number. Said another way, the MCA is

125 percent of the motor design primary RLA (incoming line) plus 100 percent of the amperage of other loads (sump heater, oil pump, purge, etc.).The MCA is listed on the chiller selection report.

Power cable sizes and conduits are discussed in “Electrical System–PowerWire Sizing,” p. 56 . If the

AFD is a remote, free-standing AFD, the MCA will be based on the compressor motor RLA.

G. Maximum overcurrent protection (MOP or MOCP).

The MOP appears on the chiller nameplate. The electrical engineer often wants to know the MOP when the chiller is selected for sizing fuses and upstream circuit breakers. Understand that the MOP is a maximum, NOT a recommended fuse size. Improperly sized circuit breakers or fuses can result in nuisance trips during the starting of the chiller or insufficient electrical protection. MOP is also NOT used to size incoming power wiring—the MCA is used for this purpose.

CTV-PRB004-EN 11



Figure 4.

Excerpt from chiller selection report

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12 CTV-PRB004-EN


Motor Protection

Historically, motor protection was provided in the starter by some type of monitoring system.

Starter manufacturers usually provide a full range of optional equipment mounted on the starter.

Eaton Cutler-Hammer ® offers IQ metering and motor protection products for their starters.

Today,Trane provides most of the key motor protection and metering functions (see Table 2 , first column) within the chiller microprocessor control panel as standard. Having the motor control and chiller control in one panel provides better integration and optimization of the two control systems.

For example, the chiller controller can unload the chiller when approaching an overload “trip” point, so that the chiller stays online.

Table 2 and Table 3, p. 14 can be used to compare the standard electrical features of the chiller controller with those of other common Eaton Cutler-Hammer ® starter-only-mounted devices.

Additional starter-mounted metering and motor protection may not be required and could be considered redundant. These devices are not available for AFDs.

Table 2.

Protection and functions by motor packages

Protection Functions

Communications

Ground fault

Long acceleration

Maximum number of starts

Momentary power loss (distribution fault)

Motor overload

Motor winding temperature

Over temperature

Overvoltage

Phase imbalance

Phase loss

Phase reversal

Run timer

Separate alarm levels (f)

Surge capacitor/lightning arrestor

Undervoltage

Tracer

AdaptiView

Optional

Optional (b)

Standard

Standard

Standard

Standard

Standard (c)

Standard

Standard (e)

Standard

Standard

Standard

Standard

Standard

Optional

Standard (e)

MP 3000

Optional

Standard

Standard

Standard

N/A

Standard

Optional (d)

N/A

N/A

Standard

Standard

N/A

Standard

Standard

N/A

N/A

(a) IQ 150

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Optional

N/A

N/A

N/A

IQ DP 4130

N/A

N/A

N/A

N/A

Optional

N/A

N/A

N/A

Standard

Standard

Standard

Standard

N/A

N/A

N/A

Standard

(a) The MP 3000 features Intel-I-Trip overload protection, enhanced custom trip curve development, UL 1053 ground fault, and advanced data logging and diagnostics.

(b) For low voltage, a Trane-supplied circuit breaker or non-fused disconnect is also required when ground fault is specified.

(c) The chiller controller monitors the motor temperatures of all three phases with one resistance temperature detector (RTD) per phase

(d) For this option, add one or two sets (three RTDs per set) of 100-ohm platinum RTDs to the motor. Contact La Crosse Field Sales Support.

(e) Under/over phase-voltage sensors include volts per phase, kW, power factor, kWh, and under/overvoltage. A required pick on medium-voltage starters.

(f) Three alarm levels are used: warning only, nonlatching (auto-reset), and latching (manual reset required).

CTV-PRB004-EN 13



Table 3.

Starter ONLY: metering functions and accuracies

Metering Functions

Ampere demand

Tracer AdaptiView

N/A

MP 3000 (a)

N/A

IQ 150

Standard (±0.25%)

IQ DP 4130

Standard (±0.3%)

Current (%RLA)

Current (3-phase)

Voltage (3-phase)

Frequency

Standard (±3% to ±7%) Standard

Standard (±3%) Standard

Standard (b) (±2%)

N/A

N/A

N/A

N/A

N/A

Standard (b) (±5%)

Standard (b) (±5%)

N/A

N/A

N/A

N/A

N/A

Standard (±0.25%)

Standard (±0.25%)

Standard

N/A

Standard (±0.3%)

Standard (±0.3%)

Standard

Standard (31 st )

Standard (31 st )

Harmonic distortion current

Harmonic distortion voltage

Kilowatt

Power factor

VA (volt-amperes)

VA demand

VA hours

VARs (volt-amperes reactive)

VAR demand

VAR-hours

Watt, see Kilowatt

Watt demand

N/A

N/A

N/A

N/A

N/A

N/A

Standard (b)

Standard

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Standard

Standard (±0.5%)

Standard (±0.5%)

Standard (±0.5%)

Standard (±0.5%)

Standard (±0.5%)

Standard (±0.5%)

Standard (±0.5%)

Standard (±0.5%)

N/A

Standard

Standard (±0.6%)

Standard (±0.6%)

Standard

Standard (±0.6%)

Standard (±0.6%)

Standard

Standard (±0.6%)

Standard (±0.6%)

Watt-hours Standard N/A Standard (±0.5%) Standard

(a) The MP 3000 features Intel-I-Trip overload protection, enhanced custom trip curve development, UL 1053 ground fault, and advanced data logging and diagnostics.

(b) Under/over phase-voltage sensors include volts per phase, kW, power factor, kWh, and under/overvoltage. A required pick on medium-voltage starters.

Overload protection

Overload or overcurrent protection shields the motor from small levels of overcurrent ranging from

107 to 140 percent of the primary RLA of the chiller. In contrast, fuses and circuit breakers are used to protect against short-circuit currents which may range to well over 100,000 amps.

Inductive loads, such as a chiller motor, behave differently than resistive loads such as electric heaters. Their current draw is greatest at startup and corresponds to the existing load when running. In other words, a motor operating normally draws rated amps (RLA) at rated load, fewer amps at less-than-rated load and more amps at greater-than-rated load. It is the latter condition that requires overload protection.

Adding an overload protection device prevents the motor from drawing more than its rated amperage for an extended period. Basic overload devices simply open the circuit when current draw reaches the “trip” point. More sophisticated devices attempt to restore normal motor operating conditions by reducing the load, but will disconnect the motor if overloading persists.

As with most overload devices, the chiller controller determines the “trip time” by measuring the magnitude of the overload. It then compares the overload to the programmed RLA “time-to-trip” curve. At startup, the standard overload protection is bypassed for the starter’s acceleration time, or until the motor is up to speed. Refer to Figure 5, p. 15 for the chiller controller’s overload timeto-trip curve.

14 CTV-PRB004-EN


CTV-PRB004-EN


Figure 5.

Tracer AdaptiView chiller controller overload time-to-trip curves

25

20

Overload Trip

Time (sec)

15

10

5

0

Nominal

Minimum

Maximum

102 108 114 120 126 132 138 144 150

% Run-Load Amps

Overload situations, left unchecked by protection, can cause excessive motor heat, that can permanently damage the windings and lead to motor failure. The time until motor damage depends mainly on the magnitude of the overcurrent and has an inverse time versus current relationship. The greater the overcurrent, the less time it takes to cause motor damage.

Overcurrent can be the result of motor overload, low line voltage, unbalanced line voltage, blocked load (rotor cannot freely rotate), single phasing, bad connections, broken leads, or other causes.

It can occur in any one winding, a set of windings, or in all the motor windings.

The threshold of overcurrent is generally the primary RLA, which may be raised for service factor or lowered due to any derating factor, such as ambient temperature or line-voltage imbalance.

Overload protection is bypassed during a start due to the high currents associated with locked rotor and motor acceleration. Maximum allowed acceleration times per the AdaptiView unit controller are listed in Table 4 .

Table 4.

Long acceleration protection

Starting Method

(starter type)

Wye-Delta

Solid-State

Variable-Frequency Drive

Across-the-Line

Primary Reactor

Autotransformer

27

12

6

16

16

Maximum Setting for the

Acceleration Timer (sec)

27

Motor overheat protection

The unit controller monitors the motor winding temperatures in each phase and terminates chiller operation when the temperature is excessive. This feature also prevents the chiller from starting if the motor temperature is too high.

Momentary power loss protection (distribution fault)

Momentary power losses longer than two or three line cycles will be detected and cause the chiller to shut down, typically within six cycles.The chiller can also shut down due to excessive or rapid voltage sags. Shutting down the chiller prevents power from being reapplied with different motor phasing.

15



Phase failure/loss protection

The chiller will shut down if any of the three-phases of current feeding the motor drop below

10 percent RLA for 2.5 seconds.

Phase imbalance protection

Based on an average of the three phases of current, the ultimate phase-imbalance trip point is

30 percent.The RLA of the motor can be derated depending on the percent of this imbalance.The

phase-imbalance trip point varies based on the motor load.

Phase reversal protection

Detects reverse-phase rotation and shuts the chiller down (backwards rotation).

Under/overvoltage protection

The chiller is shut down with an automatic reset due to excessive line voltage ±10 percent of the design voltage.

Short cycling protection

Prevents excessive wear on the motor and starter due to heating from successive starts.The unit controller uses an algorithm based on a motor heating constant and a background timer

(measuring the running time since the last start).

Supplemental motor protection

This is a set of optional motor protection features, offered as a option in addition to the Enhanced

Electrical Protection Package (see “SMP, Supplemental Motor Protection—Medium voltage only

(Enhanced Electrical Protection Package option),” p. 66 ).

16 CTV-PRB004-EN


Low-Voltage Starter Types

Table 5 shows the most common low-voltage starter types available and lists their advantages and disadvantages.Typical inrush acceleration profiles for these starters are shown in Figure 6, p. 18 .

It is very uncommon to see a full-voltage starter in a low-voltage application due to the high inrush current; however, it is represented on the chart to provide a frame of reference.

Which starter type is best?

The wye-delta starter has been around a long time and, except for an AFD, it draws the lowest inrush current.Wye-delta starters are electromechanical and service technicians are typically more comfortable with them. The solid-state starter is a relatively newer design compared to the wyedelta, and has a slightly higher inrush current in chiller applications.The solid-state starter inrush can be set lower (the starter takes longer to get the motor up to speed), but it must be above the minimum inrush required to develop the proper starting torque. The solid-state starter is comparable in price to the wye-delta starter and has a smoother inrush curve without any current spikes.The wye-delta’s transition spike is not long enough to set utility demand ratchets or reduce the life of the motor. The starter type chosen ultimately depends on the application.

Table 5.

Comparison of low-voltage starter types

Starter Type

(closed-transition

Inrush

Current

% LRA

Percent

Rated

Torque

How

Often

Used

Wye-Delta

(Star-Delta)

Solid-State

Adaptive Frequency

Drive (AFD)

33

~45

<13

(<RLA)

33

33 varies

60%

15%

25%

Advantages Disadvantages

Typical

Acceleration

Time

(seconds)

• Equal reduction of torque and inrush current

• Low cost

• Can be unit mounted

• Only applicable up to

600 volts

• “Spike” at transition

• Lowest inrush current

• Better chiller efficiency at reduced lift

• Most expensive

• Efficiency loss at full load

• Harmonics may be an issue

5–12

• Gradual inrush/ramp up

• No “spike” at transition

• Price comparable to the wyedelta

• Higher level of service expertise than wye-delta

• Higher inrush current than wye-delta

• Starting harmonics may be an issue

5–12

8–30

Trane Adaptive Frequency Drives provide motor control, but they are much more than just starters.

They also control the operating speed of the compressor-motor by regulating output voltage in proportion to output frequency. Varying the speed of the compressor-motor can translate into significant energy savings.

Applications that favor the use of an AFD exhibit increased operating hours at reduced condenser water temperatures and high energy costs. However, it is important to recognize that all variablespeed drives, including theTrane AFD, require more energy near full-load design conditions, often coinciding with the peak electrical demand of the building. This may result in higher demand charges and diminish the overall energy savings. An analysis of the full-year operation of the chiller plant using an hour-by-hour simulation program that does not use blended kW and kWh energy rates will help determine whether an AFD is appropriate for a specific application and location.

Unit or remote mounted?

Unit-mounted starters can save on installed cost and space, and they can be tested in the factory and shipped on the chiller in a NEMA 1 enclosure. Remote-mounted starters provide more options for multiple starter lineups, and may be chosen in order to implement some of the industrial starter options such as high-fault and NEMA 12/3R.

CTV-PRB004-EN 17



Figure 6.

Comparison of low-voltage starting current

120

100

80

60

40

20

0

0

X-Line

Solid-State

Wye-Delta

AFD

1 2 3 4 5

Time (seconds)

6 7 8 9 10

Low Voltage—Wye-Delta

Wye-Delta Starters

One of the most common starters in the industry is the wye/star-delta. It is an electromechanical starter initially set up in a “wye” or “star” configuration, then it transitions to a “delta” configuration during the starting sequence.To illustrate a typical starting sequence using a generic

(non-Trane) schematic, refer to Figure 7, p. 19 and its “Starting sequence,” p. 19 .

18 CTV-PRB004-EN



Figure 7.

Simplified wye-delta wiring schematic

LINE

VOLTAGE

WYE-DELTA

STARTER WIRING

CTV-PRB004-EN

F

OL

OL

OL

1M

2M

1M

2M

1M

2M

R 1A

S

R 1A

S

R 1A

S

MOTOR

CPT

F

START-

STOP

PR 1A 2M

S

1M S

TRANSITION

PR

S

1M

2M

1A

Starting sequence

1. The “start” signal from the CenTraVac controller energizes the pilot relay (PR).

2. The PR contacts close to energize the star contactor (S).

3. The S contacts close to connect the motor in the star configuration.

4. An S interlock closes to energize the start contactor (1M).

5. The 1M contacts close to connect the motor to the line.

6. A time delay relay or current monitoring device initiates transition by energizing the resistor contactor (1A).

7.

1A contacts close to connect the resistors to the line in the star configuration and in parallel with the compressor motor.

8. A 1A interlock now opens to de-energize the S contactor.

9. The S contacts open to connect the resistors and motor windings in series in the delta configuration.

10. An S interlock closes to energize the run contactor (2M).

11. The 2M contacts close to bypass the resistors and connect the compressor motor directly to the line in the delta configuration.

Dimensions

The typical unit-mounted wye-delta starter size is shown in Figure 9, p. 20 . Typical remotemounted one-, two- and three-door starter sizes are shown in Figure 10, p. 20 , Figure 11, p. 20 , and

Figure 12, p. 21 . Always consult the submittal drawings for as-built dimensions.

19



The one-door remote-mounted starter size is generally used for 155- to 606-amp starters with no disconnect.The two-door size is used for 640- to 1,700-amp starters with no disconnect.The threedoor size is used for 1,385- to 1,700-amps when disconnects are included.

Figure 8.

Unit-mounted WD Figure 9.

Remote 1-door WD

Squirrel-cage

Stator

60”

Rotor shaft

13.5”

38.5”

84”

Stator

19.3”

32”

Figure 11. Remote 3-door WD Figure 10. Remote 2-door WD

Stator

Squirrel-cage

84”

Rotor shaft

84”

Stator

19.3” 19.3”

56”

84”

20 CTV-PRB004-EN



Figure 12. Unit-mounted, wye-delta starter

2

1

2

1. Top-entry power only

2. 4 kVA control-power transformer

3. Circuit breaker (optional)

4. Transition resistors

3

CTV-PRB004-EN

4

Standard features

• Unit or floor mounted

• Control-power transformer

• Padlock tab for additional locking of the starter door

• Line-side connection terminal block/main lug only

• UL and CUL certified

• Environmental specification

• Designed, developed, and tested in accordance with UL 508

• NEMA 1 enclosure as standard

• Operation from sea level to 6,000 ft (1,829 m)

• Operating ambient temperature range 32°F to 104°F (0°C to 40°C)

• Relative humidity, non-condensing 5 percent to 95 percent

• Non-operating ambient temperature range -40°F to 158°F (-40°C to 70°C)

• Voltage utilization range ±10 percent

21



Low Voltage—Solid-State

Solid-State Starters

TheTrane ® solid-state starter produces a soft start with a gradual inrush current and no transition spikes. It controls the starting characteristics of a motor by controlling the voltage to the motor. It does so through the use of silicon controlled rectifiers (SCRs), which are solid-state switching devices, and an integral bypass contactor for power control. An SCR will conduct current in one direction only when a control signal (gate signal) is applied. Because solid-state starters use alternating current (AC), two SCRs per phase are connected in parallel, opposing each other so that current may flow in both directions. For three-phase loads, a full six-SCR configuration is used, as shown in Figure 13 .

Figure 13.

Six-SCR arrangement

L1 T1

L2 T2

L3 T3


During starting, control of current or acceleration time is achieved by gating the SCRs “on” at different times within the half-cycle.The gate pulses are originally applied late in the half-cycle and then gradually applied sooner in the half-cycle. If the gate pulse is applied late in the cycle, only a small increment of the wave form is passed through, and the output is low. If the gate pulse is applied sooner in the cycle, a greater increment of the wave form is passed through, and the output is increased. By controlling the SCRs’ output voltage, the motor’s acceleration characteristic and current inrush are controlled as illustrated in Figure 14 .

Figure 14. Starting sequence wave forms

22

25% voltage 50% voltage full voltage

When the SCRs are fully “phased on,” the integral bypass contactors are energized. The current flow is transferred from the power pole to the contactors.This reduces the energy loss associated with the power pole, and extends contactor life. When the starter is given the stop command, the

SCRs are gated “full voltage” and the bypass contactor is de-energized. The current flow is transferred from the contactors back to the power poles. Less than one second later, the SCRs are turned off and the current flow stops.

CTV-PRB004-EN



Features

• Unit- and floor-mounted models are available


• Starting current is factory set and field adjustable

• Starting torque is factory set and adjustable via a voltage “notch” setting

• Six-SCR power section

• Air-cooled design with bypass contactor eliminates need for a water-cooling circuit, pump, and heat exchanger

• Bypass contactor rated to carry 100 percent of the full-load motor phase current

• Protection from shorted SCRs and high starter heatsink temperature

• Protection from transient voltage through resistor-capacitor (RC) snubbers across SCRs and metal oxide varistors (MOVs)

• Padlock tab for additional locking of starter door

• Line-side connection terminal block/main lug only

• UL and CUL certified

Dimensions

Typical dimensions for unit- or remote-mounted solid-state starters are shown in Figure 15 . Always consult the submittal drawings for as-built dimensions.

Figure 15. Solid-state dimensions

60"

13.5"

38.5"

CTV-PRB004-EN 23



Figure 16. Unit-mounted, solid-state starter

1

2

1. Top-entry line power

2. Intelligent technology (IT) controller

3. Starter control board

4. Potential transformers


24

3 4 5

Environmental specification





• Relative humidity, non-condensing 5% to 95%


• Voltage utilization range ±10%

CTV-PRB004-EN



Low Voltage—Unit-Mounted Adaptive Frequency Drive

TheTrane Adaptive Frequency Drive is a refrigerant-cooled, microprocessor controlled design.The

AFD is used in lieu of a constant-speed starter and is currently available for use with 460 or 480 volts only. Adaptive Frequency is a trademarked term for the Trane ® variable-speed drive, using proprietary control logic and made to Trane specifications.

About the Trane AFD

The AFD is unit-mounted and ships completely assembled, wired, and tested from the factory.The

AFD controller is designed to interface with the chiller controller. It adapts to the operating ranges and specific characteristics of the chiller.The optimum chiller efficiency is created by coordinating the compressor-motor speed with the compressor inlet guide vanes.The chiller controller and the

AFD controller work together to maintain the chilled-water setpoint and avoid surge. If surge is detected, the chiller controller’s surge-avoidance logic in the chiller controller makes the proper adjustments to move the operating point away from surge.

How it works

The frequency drive regulates output voltage in proportion to output frequency to maintain ideal motor flux and constant torque-producing capability. Or put simply, a variable-speed drive controls load-side frequency and voltage to adjust the compressor motor speed. The AFD is a voltagesource, pulse-width modulated (PWM) design. It consists of three primary power sections as shown in Figure 17 : the active rectifier, the DC bus, and the inverter.

Figure 17. AFD power sections

CTV-PRB004-EN

Rectifier (active).

Takes incoming AC power, filters it with an LCL filter (not shown), and then converts it to a fixed DC voltage. The insulated-gate bipolar transistor (IGBT) active rectifier significantly reduces the amount of line-side harmonic levels and the amount of ripple on the DC bus. The active rectifier also has some traditional post-generation filtering capabilities to further smooth out remaining line-side harmonics.

DC bus.

Capacitors store the DC power provided by the rectifier until it is needed by the inverter.

Inverter.

Converts the DC voltage into a synthesized AC output voltage.This synthesized output controls both the voltage and the frequency.The synthesized output waveform consists of a series of pulses, hence the “pulse” in PWM.


Trane AFDs are programmed to start the compressor motor using low frequency and low voltage, thereby minimizing the inrush current. The motor is then brought up to speed by gradually increasing both frequency and voltage at the same time.Thus, current and torque are much lower during startup and motor acceleration than the high current, high torque associated with acrossthe-line or even reduced-voltage starters; refer to the inrush current vs. time graph ( Figure 6, p. 18 ).

25



Figure 18. Trane AFD

• The AFD is rated by output current and is limited to a maximum of 100-percent continuous RLA

(rated-load amps) by theTrane ® chiller unit controller. A 100-percent output current capability results in 100-percent torque generated by the motor.

1

2

5

3

1.

Pre-charge contactor

2. Inductor (behind the panel)

3. Adjustable-speed drive

(inverter)

4. Circuit breaker (standard)

5. Active rectifier


4

6

26

Features

The standard design features for the AFD include:

• NEMA 1, ventilated enclosure with a hinged door, tested to a short-circuit current rating of

65,000 amps.

• Padlock-able, door-mounted circuit breaker/shunt trip with an AIC rating of 65,000 amps.

• SCCR/AIC rating of 100,000 amps available as a design special.

• UL/CUL listed as a package.

• Simple, modular construction.

• 480/60/3 input power ±10 percent, with drive overload capability of 100 percent continuous to

150 percent for five seconds.

Note: For voltages other than 460/480 V, a transformer is currently needed to produce

460/480 V.

• Motor thermal overload protection 102 percent continuous, 108 percent for 60 seconds,

140 percent for 1.5 seconds.

• Minimum efficiency of 97 percent at rated load and 60 hertz.

• Soft-start, controlled acceleration, coast-to-stop.

• Adjustable frequency from 38 to 60 hertz.

• Control circuit voltages physically and electrically isolated from power circuit voltage.

• 150 percent instantaneous torque available for improved surge control.

• Output line-to-line and line-to-ground short-circuit protection.

• Ground fault protection (UL listed).

CTV-PRB004-EN


CTV-PRB004-EN



• 32°F to 104°F (0°C to 40°C) operating ambient temperature.

• Altitude to 3,300 feet (1,000 m), amperage derate of 1 percent per every 300 feet above

3,300 feet.

• Humidity, 95 percent non-condensing.

Dimensions

Typical dimensions for the unit-mounted Adaptive Frequency Drive are shown in Figure 19 and

Figure 20 . Always consult the submittal drawings for as-built dimensions.

Figure 19. AFD dimensions

(405- and 608-amp design)

Figure 20. AFD dimensions

(900- and 1,210-amp design)

Door swing

32.5" & 24.5" from front of AFD

62"

Each door swing is 31 " from front of AFD

75"

18"

26"

60"

98"

Motor-AFD mutual protection

The chiller unit-controller capabilities allow the control/configuration interface to, and the retrieval/ display of AFD-related data. AFD standard design features controlled through the Tracer

AdaptiView™ include:

• Current limited to 100 percent.

• Motor overload protection.

• Motor over-temperature protection.

• Phase loss, phase reversal, and phase imbalance protection.

• Undervoltage and overvoltage protection.

• Output speed reference via IPC3 communication bus from the chiller controller to the AFD.

Digital data display

The following points are digitally displayed at the chiller controller:

• Output speed in hertz

• Output speed in rpm

• Input frequency

• Input/output line voltage

• Input/output kW

• Input/output current

• Average output current in percent RLA

• Load-side power factor

• AFD transistor temperature

• Fault

27



Harmonics

Harmonics has become a frequently used term in the power quality arena. Of all the power quality issues encountered today, harmonics is the least understood and most feared; unfortunately, this has resulted in overstating the impact of harmonics.

Harmonics is not a “thing” but a way to define current or voltage distortion on a power line.

Harmonics can be directly linked to nonlinear loading of a power system. Nonlinear loads are created by devices connected to a given power system that draw current from the power source with a waveform that is not a pure sine wave.

All nonlinear loads, including variable-frequency drives, will create current and voltage distortion.

Typically harmonics is not an insurmountable issue when applying an AFD on a centrifugal chiller.

Harmonic attenuation

Harmonic attenuation is standard on the unit-mounted refrigerant-cooled AFDs and includes:

• Integrated active rectification control of the building AC power assures low line-generated harmonics back to the user’s power grid. This results in less than 5 percent current harmonic distortion (TDD) as measured at the AFD.

• Active input rectifier will regulate to a displacement power factor of 0.98 or better at full load and a value of 0.96 at part load.

• Full motor voltage is applied regardless of the input voltage.

Note: TDD is a direct affect of variable-frequency drives and is a larger and more critical value than the amount of total harmonic distortion (THD). As measured at the AFD, the amount ofTHD will be less than the TDD.

IEEE 519

It is important to recognize that IEEE 519 relates to the entire system, not specifically to any one load or product. IEEE 519 establishes requirements at the point of common coupling (PCC) where the building connects to the utility system. The standard contains no specific requirements for the internal electrical loads.

Even though Trane AFD-equipped chillers will attenuate their own harmonics, other nonlinear loads on the same system could still create harmonic problems. In buildings where harmonics might be a concern, Trane recommends conducting a power-distribution system analysis to determine if there is a need to further attenuate harmonics at the system level.

Low Voltage—Remote-Mounted Adaptive Frequency Drive

Depending on the application,Trane also offers a remote free standing Adaptive Frequency Drive

(AFD). The remote AFD comes as a complete, free-standing package that includes the necessary controls, control power and programming needed for operation. EachTrane Adaptive Frequency

Drive arrives completely programmed with all chiller control communication logic installed. Input voltage options include 460, 480, 575, and 600 volts. Most of the low-voltage AFDs in the industry are designed to work at 460/480 volts only. In HVAC applications were the voltage is 575/600, a transformer would be need to apply an AFD. With theTrane remote AFD, a transformer would not be needed, thereby eliminating the associated extra design time, space requirements, installation costs and energy losses.

The design

The remote AFD design is a voltage-source, pulse-width modulated (PWM) type. It consists of three primary power sections.

Rectifier.

Constructed of silicon controlled rectifiers (SCR), which convert the incoming utility AC sine wave into DC voltage that will be stored in the DC Bus section

DC Bus Section.

A capacitor bank that is used to store energy for use within the inverter section

28 CTV-PRB004-EN



Inverter IGBTs.

Use the pulse width modulation (pwM) method to convert the DC voltage from the capacitor bank into a synthesized output AC voltage that controls both the voltage and frequency applied to the motor

Figure 21. Front view, remote-mounted AFD

CTV-PRB004-EN

Features

The standard design features for the AFD include:

• Free standing NEMA 1, ventilated enclosure with a hinged door, tested to a short-circuit current rating of 65,000 amps. Enclosure locking provisions are standard.

• Lockable, door-mounted circuit breaker/shunt trip with an AIC rating of 65,000.

• Amps, and enclosure short circuit rating of 65,000 amps standard.

• UL/CUL listed as a package.

• Simple, front access only design.

• 460/480/60/3 input power ±10 percent.

• 575/600/60/3 input power ±10 percent.

• Minimum efficiency of 97 percent at rated load and 60 hertz.

• Displacement power factor at 0.96 at all loads.

• Soft-start, linear acceleration, coast-to-stop.

• Adjustable frequency from 38 to 60 hertz.


• Output line-to-line and line-to-ground short-circuit protection.

• Ground fault protection (UL listed).

Optional Items

• NEMA 12 enclosure.

• 100,000 amp enclosure short-circuit current rating (SCCR) with 100,000-amp AIC circuit breaker available as a design special.

29




• Operating temperature: 32°F to 104°F (0°C to 40°C).

• Storage temperature: -4°F to 149°F (-20°C to 65°C).

• Humidity: 95 percent non-condensing.

• Maximum elevation: 3280 ft (1000 m) rated output current.

• Derate 4 percent/3280 ft over rated altitudes up to 9840 ft (3000 m).

Dimensions

Table 6 provides some basic reference dimensions and weights for the remote AFD. Always refer and use the Trane submittals for actual dimensions.

Table 6.

Remote AFD dimensions

F3

F4

Frame

D3/D4

E2

Power (hp) Max. Amps Power (hp) Max. Amps

150–350 394 150–400 356

450–600

N/A

650–750

950–1050

1150–1350

649

N/A

791

1031

1360

450

500–650

750–1050

N/A

1150–1550

400

560

840

N/A

1258

Width (in.) Depth (in.) Height (in.) Weight (lb)

48 24 86 1220

56

64

127

127

150

24

24

24

24

24

90

90

90

90

90

1635

1680

2885

3185

3720



• Frequency command

• Input line voltage

• Load-side amps

Harmonics

The remote AFD is a standard six pulse design. Therefore the harmonic level is ~35 percent total demand distortionTDD as measured at the AFD input. If lower levels of attenuation are required, upstream filtering would be required.

30 CTV-PRB004-EN


Medium-Voltage Starter Types (2,300–6,600 Volts)

Table 7 shows the most common medium-voltage starter types available and compares inrush current, torque, frequency of use, advantages and disadvantages, and typical acceleration time.

The inrush profiles are shown in Figure 22 .


One question often asked is: “Which is better, full voltage or reduced voltage?” Because mediumvoltage starters by nature use less current than low voltage, and therefore have significantly less current inrush. Across-the-line medium-voltage starters are more commonly used; however, in certain applications reduced voltage will be used to minimize starting strain on the electrical system.

Table 7.

Comparison of medium-voltage starters (2,300–6,600 volts)

Starter Type

(closed-transition)

Inrush

Current

% LRA

Percent

Rated

Torque

How

Often

Used

Across-the-Line

(Full Voltage)

Primary Reactor

65% TAP

Autotransformer

65% TAP

AFD

100

65

45

<13

(<RLA)

100

42

42

Varies

27%

49%

22%

2%

Advantages

• Low cost

• Least complex

• Least maintenance

• Good compromise between first cost and inrush current reduction

• Almost equal reduction of torque and inrush current

• Lowest inrush current

• Efficiency at part lift

• Power factor

Disadvantages

Typical

Acceleration

Time

(seconds)

• Draws highest inrush current at startup 3–5

• More expensive than Acrossthe-Line

• Larger than Across-the-Line

5–12

• Most expensive

• Larger than Across-the-Line 5–12

• Very expensive

• Large and heavy

• Complex

5–12

Figure 22. Comparison of medium-voltage starting current

120

100

80

60

Across-the-Line

Primary Reactor (65% tap)

Autotransformer (65% tap)

AFD

40

20

0

0 1 2 3 4 5 6

Time (seconds)

7 8 9 10

Unit- or remote-mounted?

Unit-mounted medium-voltage starters can save on installed cost and space.They are tested in the factory and are shipped on the chiller. Remote-mounted starters are sometimes bussed together in various configurations as shown in “Multiple Starter Lineups (2,300–6,600 volts),” p. 61 . Remotemounted starters fromTrane can have special NEMA options, whereas unit-mounted starters are

NEMA 1. All starters conform to ANSI/NEMA ICS-6 enclosure standards unless otherwise noted.

CTV-PRB004-EN 31



Other options for remote-mounted starters are available in the Enhanced Electrical Protection

Package (see “Industrial-Grade Starters,” p. 63 .)

NEC 2005 changes for medium-voltage (2,300–6,600 volt) wire

NEC code for 2005 requires that medium-voltage cable is shielded. This affects the power wire selection and connection provisions to the chiller, and between the chiller and starter when it is remote mounted. When you use shielded cable, you must also use stress cones at the termination points (motor terminal connection, remote starter, or unit-mounted starter connection). Stress cones are composed of electrical shielding wrap and are typically 9–12 inches in length. Stress cones are used to confine the dielectric field and reduce electrical stresses at the termination point.

Trane ® unit-mounted medium-voltage starters now ship with a field-installed accessory “top hat” that is shown in our as-built submittal drawings. The top hat is enclosed in the starter cabinet during shipment and then reversed for field installation. Motor terminal boxes and remotemounted starters are designed to accommodate stress cones without an additional enclosure.

Refer to the appropriate submittals drawings to verify that the starter has sufficient connection space for your requirements. For more information regarding the top hat , refer to “Unit-Mounted

Starter Top Hat—NEC 2005 Code Requirement,” p. 40 .

Medium Voltage—Across-the-Line (2.3–6.6 kV)

Across-the-Line Starter (2,300–6,600 volts)

Figure 23, p. 33 shows a schematic for the most basic starter type; the across-the-line (X-Line) starter, which is also known as a full-voltage starter.To illustrate a typical starting sequence using a generic (non-Trane) schematic, refer to Figure 23, p. 33 and the starting sequence below.


1. A “start” signal from the chiller controller energizes the pilot relay (PR).

2. The PR contacts close to energize the start/run contactor (1M).

3. The 1M contacts close to connect the compressor motor directly to the line.

32 CTV-PRB004-EN



Figure 23. Simplified across-the-line wiring diagram

LINE

VOLTAGE

ACROSS-THE-LINE

STARTER WIRING

CTV-PRB004-EN

1M

1M

1M

OL

OL

OL

F

CPT

F

START-

STOP PR

PR

1M

Figure 24. Unit-mounted, across-the-line starter dimensions

Top Hat

9.13"

MOTOR

27"

26.2"

60"

40"

20"

38"



• Primary and secondary current transformers (CTs)

• Potential transformers (PTs)

33



• Grounding provisions

• Bolted line-power connections

• Bolted load-side connections for remote starters

• Standard motor protection









Dimensions

Typical dimensions for unit- and remote-mounted across-the-line starters are shown in Figure 24, p. 33 and Figure 25, p. 34 . Always consult the submittal drawings for as-built dimensions.

Figure 25. Remote-mounted XL

80"

36"

30"

34 CTV-PRB004-EN



Figure 26. Unit-mounted, across-the-line, medium-voltage starter

1

1. Top-entry power connection

2. Current-limited power fuses

3. Vacuum contactors

4. Low-voltage section

5. Isolation switch

(provision for one lock)

6. Control-power transformer

2

3

4

5

6

Medium Voltage—Primary Reactor (2.3–6.6 kV)

Primary Reactor Starter (2,300–6,600 volts)

One of the most common starters in the industry is the primary reactor. To illustrate a typical starting sequence using a generic (non-Trane) schematic, refer to Figure 27, p. 36 and the starting sequence below.



2. The PR contacts close to energize the start contactor (1M).

3. The 1M contacts close to connect the compressor motor to the line with the motor in series with the reactor.

4. A time delay or current monitoring device initiates transition by energizing the run contactor

(2M).

CTV-PRB004-EN 35



5. The 2M contacts close to bypass the reactor and connect the compressor motor directly to the line.

Figure 27. Simplified primary reactor wiring diagram

LINE

VOLTAGE

36

1M

1M

1M

OL

PRIMARY REACTOR

80% 65%

50%

2M

OL 2M

OL 2M

MOTOR

F

CPT

F

START-

STOP PR

PR

1M

2M

TRANSITION

















Dimensions

Typical dimensions for remote-mounted primary reactor starters are shown in Figure 28, p. 37 .

Unit-mounted primary reactor starter dimensions are shown in Figure 29, p. 37 . Always consult the submittal drawings for as-built dimensions.

CTV-PRB004-EN



Figure 28. Remote-mounted, reduced-voltage starter dimensions

80"

30"

72"

Figure 29. Reduced-voltage, unit-mounted starter dimensions

Top Hat

9.13"

Reduced-Voltage

Section (mounted on the condenser)

60"

27"

26.2"

40"

20"

38"

CTV-PRB004-EN 37



Figure 30. CenTraVac with a reduced-voltage autotransformer starter (CH530 unit controller)

Medium Voltage—Autotransformer (2.3–6.6 kV)

Autotransformer Starter (2,300–6,600 volts)

Another medium-voltage starter type is the autotransformer. To illustrate a typical starting sequence using a generic (non-Trane) schematic, refer to Figure 31, p. 39 and the starting sequence below.



2. The pilot relay contacts close to energize the shorting contactor (S).

3. The S contacts close to complete the autotransformer circuit.

4. An S interlock closes to energize the start contactor (1M).

5. The 1M contacts close to connect the compressor motor to the line with the motor in series with the autotransformer.

6. A time-delay relay or current-monitoring device initiates transition by energizing the transition relay (T).

7. The T contacts open to de-energize the S contactor.

38 CTV-PRB004-EN


CTV-PRB004-EN


8. The S contacts open to open the autotransformer circuit.

9. The autotransformer is now connected as a series reactor with the motor.

10. Now, a secondT interlock and a second S interlock both close to energize the run contactor (2M).

11. The 2M contacts close to bypass the transformer and connect the compressor motor directly to the line.

Figure 31. Simplified autotransformer wiring diagram

LINE

VOLTAGE

F

1M

1M

1M

OL

OL

OL

AUTO-TRANSFORMER

2M

S

2M

S

50%

65%

80%

100%

MOTOR

CPT

F

START-

STOP

PR T 2M

1M

S

T

TRANSITION

S

PR

S

1M

T

2M

















39



Dimensions

Typical dimensions for both unit-mounted and remote-mounted autotransformer starters are the same as the primary reactor starters shown in Figure 28, p. 37 and Figure 29, p. 37 . A chiller with a unit-mounted autotransformer starter is pictured in Figure 30, p. 38 . Always consult the submittal drawings for as-built dimensions.

Solid state medium-voltage starters

If you look at the medium-voltage chiller industry, there are three primary electro-mechanical starter types commonly used: 1) Full Voltage (X-Line), 2) Primary Reactor, and 3) AutoTransformer.

Of these, X-Line and Primary Reactor make up a majority of the business. The balance is in

AutoTransformer and some solid state. Cost increases as you move from X-Line to

AutoTransformer, as does the relative complexity, and size.These starters are considered simple to begin with in comparison to solid state starters; however, we always want to use the simplest design if the performance (inrush level) meets the requirements of the application.This is why the

X-Line type is often used at this voltage, because the amps are generally low to begin with based on the voltage class (i.e., 4,160 volts). Trane has shipped thousands of chillers and starters with these electromechanical starter types. We know of no better way to offer the highest reliability, lowest inrush, and still meet the 30-year life expectancy.

Over the years solid state starters have been available, however when the pros and cons are evaluated, a traditional electro-mechanical is typically the best choice. Many claim that the solid state is a “soft starter.” What does this really mean? For most, this means a ramped inrush profile with no transients; however, because we are dealing with large induction motors, the ramp-up is quick to enable the required torque. We think you need to look at the inrush magnitude, and when you review the starter types, the primary reactor is very comparable to a solid state. However, the cost of the primary reactor is typically less, it is simpler, more reliable, does not have harmonic aspects to consider, and is easier to service and maintain. In the end, the decision is up to the customer.

Unit-Mounted Starter Top Hat—NEC 2005 Code Requirement

As outlined in “Unit-Mounted Starter Top Hat—NEC 2005 Code Requirement,” p. 40 , NEC 2005 code requirements specify the use of shielded cables and stress cones for medium-voltage wiring.

For Trane ® unit-mounted medium-voltage starters (and “SMP, Supplemental Motor Protection—

Medium voltage only (Enhanced Electrical Protection Package option),” p. 66 ) a supplementary enclosure, or top hat , is shipped in the starter cabinet in order to fully enclose the incoming wire and stress cones terminated at the starter.The

top hat is shipped inverted in the starter cabinet to avoid damage and must be properly configured in the field.The unit-mounted top hat is shown in

Figure 32, p. 41 .

40 CTV-PRB004-EN



Figure 32. Top Hat placement for shipment and installation

Sheet Metal “Top Hat” Section

(allows space for shielded cable/stress cones—field provided)

Stowed for Shipment Installed for Stress Cones

CTV-PRB004-EN 41



Medium Voltage—Remote-Mounted Adaptive Frequency Drive

The Trane AFD is a remote-mounted air-cooled, microprocessor based pulse width modulation

PWM design.The AFD use a “direct to drive” design that connects the power supply directly to the medium voltage drive with out the use of an isolation transformer. The AFD is a current source inverter that uses Symmetrical Gate Commutated Thyristors (SGCTs) power semi-conductor switches in both the rectifier and inverter sections.The active front end rectifier and common mode choke blocks any common mode voltages, smooths the DC current, and mitigates the motor neutral to ground voltage. Because there is no negligible common mode voltages and currents, no special compressor bearing provisions are required.The design does not generate dv/dt or reflected wave voltage that can stress the motors. As a result, standard duty medium voltage motors can be used with the AFD.

The AFD includes a line starter contactor and current limiting power fuses and a lockable non-load break isolation switch as standard.The fuses are installed via fuse clips and can be replaced without special tools. An integral common mode choke with iron core eliminates the need for semiconductor fuses which reduce nuisance trips. The AFD ships as a single, free-standing enclosure

(with a small exception of small top hat sections), wired, and tested to the job site.

Figure 33. Front view, medium voltage remote-mounted AFD

42

Remote AFD Design Features

• NEMA 1 ventilated, gasketed enclosure with hinged doors.

• Design access from the front only. The patented PowerCage inverter and rectifier module allows easy access to main power components without the use of special hardware. Power switch components are replaceable without removal of the entire power module.

• Paint—All exterior metal parts are painted with hybrid epoxy powder paint ANSI 49 medium grey. The low voltage section is color coded black for safety.

• The entire package is UL/CUL listed.

Other AFD features include:

• Simple modular design.

• Compact, light weight design.

• Designed for minimum availability of 99.9 percent.

• Typical mean time between failure is 180,000 hours.

• Minimum predicted life expectancy is 20 years.

• The AFD is rated for the nominal chiller voltage ±10 percent.

CTV-PRB004-EN



• Displacement power factor is 0.96 at all loads.

• Efficiency is 97.7 percent at rated load, 60 Hz.

• Soft-start; linear acceleration; coast to stop.

• All control circuit voltages are physically and electrically isolated from the power circuit voltage.


• Output line-to-line and line-to-ground short circuit protection.

• Input protection via surge arrestors.

• Kirk key for interlocking the system which prevents unsafe access to doors.

• General AFD protection—The AFD includes a comprehensive set of protection features segmented into the following three categories: 1) Line side level, 2) System level, and 3) Load side level. For more information, refer to the Installation, Operation, and Maintenance manual.

• Near sinusoidal voltage and current waveforms to the motor at all speeds and loads. Output current THD is less than 5 percent.

• The control power monitoring system monitors all power.

• Power switch device diagnostics detect and protect against device short, over or under gate voltage loss, of gating, loss of diagnostic feedback, heat sink temperature feedback as well as overload monitoring and protection.

• The drive system shall provide controlled speed over the range from 38 to 60 Hz.

• The AFD has a “normal duty” rating of 100 percent continuous current with a short time duty rating of 110 percent overload for one minute, once every 10 minutes.

Chiller Unit Control Features for the AFD

The chiller unit control panel capabilities provide for the control/configuration interface to—and the retrieval/display of—AFD-related data. AFD standard design features controlled through Tracer

AdaptiView include:

• Current limited to 100 percent at start, no inrush, true soft start

• Motor overload protection

• AFD over temperature protection

• Phase loss, phase reversal, and phase imbalance protection

• Overvoltage and undervoltage protection

Digitally-displayed AFD parameters on the AdaptiView panel: output speed in hertz, output speed in rpm, input frequency, input/output voltage, input/output kW, output/load amps, average input current, average current in % RLA, load power factor, fault, AFD temperature

In addition, on the AFD enclosure there is a 16-line, 40-character LCD display that can be utilized by operators as needed. It includes a full comprehensive list of AFD performance parameters. refer to the Installation, Operation, and Maintenance manual and the AFD manufacturer’s documentation.

The AFD is designed for top entry line power and top or bottom load power exit.The power cable connections are bolted type. Lugs are not provided. Use copper conductors only for terminal connections. Failure to do so may cause corrosion or overheating, and AFD damage.

Environmental Ratings

• -40°F (-40°C) to 158°F (70°C) storage ambient temperature range.

• 32°F (0°C) to 104°F (40°C) operating ambient temperature range.

• Altitude to 3280 ft (1000 m), amperage derate output current above rated altitude up to 9840 ft

(3000 m).

• Humidity, 95 percent non-condensing.

Design Notes

The AFD should be located within 150 ft of the chiller. If this distance must be exceeded due to application requirements, contact your local Trane representative.

CTV-PRB004-EN 43



The AFD is designed for a maximum operating temperature of 104°F. However, optimal operation and design life will be experienced if the ambient temperatures are kept well below this maximum.

The maximum AFD heat rejection is listed on the AFD submittal drawing in this package. Additional equipment room cooling provisions may be required.

For all remote medium voltage AFDs, note that 4 kVA at 120-volt control power must be provided to the chiller control panel, and this is customer supplied. Refer to the wiring diagrams in the submittal package.

On some larger Frame B AFDs, note that the AFD itself requires a separate 8 kVA at 480-volt power supply. This is in addition to the main power supply voltage.

Installation Notes

The AFD ships as a single enclosure, except for some “top hat” enclosures.These top hat sections must be field installed. Refer to the AFD drawings for more information.

It is suggested that the AFD be placed on a housekeeping pad; anchoring the AFD to the ground is not a manufacturer’s requirement. Consult local codes.

Refer to the AFD installation, operation, and maintenance manual, AFDJ-SVU01A-EN ( Installation,

Operation, and Maintenance: Remote-Mounted Medium Voltage Air-Cooled Adaptive Frequency

Drive withTracer AdaptiView Control ), or the most recent revision, for more detailed information on AFD installation, operation and maintenance requirements.

Dimensions

See the specific submittals for the application. In general, for the the 4,160-volt class, the geometry is as follows for the two frame sizes:

A Frame.

RLA from 61–140 amps nominal at 4,160 V

94” wide X 40” deep X 105” high

B Frame.

RLA from 160–250 amps nominal at 4,160 V

182” wide X 40” deep X 105” high



• Output speed in hertz

• Output speed in rpm

• Input frequency

• Input/output voltage

• Input/output kW, load side amps

• Average output current in % RLA

• Average input current

• Load side power factor

• AFD temperature

• Fault

Harmonics

• Harmonic currents on the line side—Harmonics are minimized through the use of a common mode choke and active rectifier. The AFD will meet a current harmonic distortion level of

5 percent or less in total demand distortion TDD as measured at the input to the AFD.

44 CTV-PRB004-EN



Table 7, p. 31 , shows the available medium-voltage starter types for 10,000–13,800 volts.These are identical in nature to their 2,300–6,600-volt counterparts in terms of inrush current, starting torque, and their inherent advantages/disadvantages. Enclosure sizes are larger due to incoming line provisions, internal components, and electrical shielding. These starters are available in remotemounted options only due to electrical restrictions associated with these higher voltages.

Note: UL certification of these starters is not available due to AC voltage ranges exceeding

7,200 volts as specified in UL Standard 347. This includes all chiller starter manufacturers selling 10–13.8 kV refrigeration equipment. Low-voltage sections of the starters are UL rated as applicable.


In terms of starting torque and inrush current, these starters share the same advantages and disadvantages similar to the 2,300–6,600-volt starters.The major difference for 10–13.8 kV starters is the increased floor space required. If PFCCs are required, the dimensions will further increase because the capacitors require their own separate enclosure. All starters are NEMA 1 rated as standard and conform to ANSI/NEMA ICS-6 enclosure standards unless otherwise noted.

Medium Voltage—Across-the-Line (10–13.8 kV)

Across-the-Line Starter (10,000–13,800 volts)


Refer to the across-the-line starting sequence ( “Starting sequence,” p. 32 ).


• 4 kVA control-power transformer







Dimensions

Typical dimensions for a remote-mounted across-the-line starter are shown in Figure 34, p. 46 .

PFCCs, if required, are housed in a 36-inch wide auxiliary cabinet (not shown). Always consult the submittal drawings for as-built dimensions.


• Designed, developed and tested in accordance with IEC 60470, 62271-200







CTV-PRB004-EN 45



Figure 34. Remote-mounted, across-the-line dimensions

MAIN BUS

INCOMING

LINE

LOW-VOLTAGE

SECTION

95"

46

36"

60"

Figure 35. Remote-mounted, 11-kV, across-the-line starter

1.

Current-limiting power fuses

2. Isolation switch (provision for one lock)

3. Control-power transformer

4. Vacuum contactors

1

2

3 4

CTV-PRB004-EN



Medium Voltage—Primary Reactor (10–13.8 kV)

Primary Reactor Starter (10,000–13,800 volts)


1.

Refer to the primary reactor starting sequence ( “Starting sequence,” p. 35 ).









Dimensions

Typical dimensions for remote-mounted primary reactor starters are shown in Figure 36, p. 47 .










Figure 36. Remote-mounted, primary reactor dimensions

MAIN BUS

MAIN BUS

MAIN BUS

INCOMING

LINE

LOW-VOLTAGE

SECTION

96"

36"

132"

CTV-PRB004-EN 47



Medium Voltage—Autotransformer (10–13.8 kV)

Autotransformer Starter (10,000–13,800 volts)


Refer to the autotransformer starting sequence ( “Starting sequence,” p. 38 ).









Dimensions

Typical dimensions for remote-mounted autotransformer starters are shown in Figure 37, p. 48 .










Figure 37. Remote-mounted, autotransformer dimensions

MAIN BUS

MAIN BUS

MAIN BUS

INCOMING

LINE

LOW-VOLTAGE

SECTION

96"

36"

132"

48 CTV-PRB004-EN


Electrical System—Ratings

CTV-PRB004-EN

“Normal” and “overload” conditions … “fault current” … “interrupt” versus “short-circuit” ratings” … “current-limiting.” Knowing what these terms mean and applying them correctly are fundamental to designing safe, reliable electrical distribution systems. This is especially true in light of more stringent code enforcement and the current design trend to deliver energy savings by selecting low-impedance transformers: How does this influence safety? Lower transformer impedances result in higher short-circuit currents.

Simply choosing a circuit breaker with a high-interrupt rating won't assure adequate protection under short-circuit conditions. An “ounce of prevention” helps avoid the code official’s “red tag” at the next system startup.The following section reviews the meaning of terms, defines some of the issues related specifically to HVAC motor starter applications, and identifies practical effective solutions.

Normal operation

“Normal operation” describes the full-load (or rated) conditions of each system component. For motors, it includes the amps initially drawn at startup, i.e. inrush current, as well as the full- or ratedload amps drawn while running. The magnitude of inrush current for a particular application depends on the motor, voltage, and type of starter used.

Normal operating conditions determine wire and transformer sizing. They are also used in conjunction with “fault conditions” to select overcurrent protection devices such as circuit breakers and fuses. Rating factors are applied, based on the type and number of connected loads, to assure that the devices selected adequately protect the motor as it starts and while it is running.

The size of the interconnecting wires between the transformer and starter reflects the type and rated amperage draw of the load, i.e. the chiller motor. Sizing the wires on this basis assures that they can carry the inrush current at startup without overheating.

Available Fault Current (AFC)

Refer to Figure 39, p. 52 , for the reference points or label locations of each rating. AFC is the calculated potential short-circuit current at a point just upstream of the starter. It is calculated by the electrical engineer and is a function of the electrical distribution system—including the transformers.

Imagine a wrench inadvertently left in a starter after servicing. Touching two power phases, it completes the circuit between them when the panel is energized. This results in a potentially dangerous situation, or “fault condition,” caused by the low-impedance phase-to-phase or phaseto-ground connection … a “short circuit”.

Fault current, also called “short-circuit current” (I sc

), describes the amount of current flow during a short. It passes through all components in the affected circuit. Fault current is generally very large and, therefore, hazardous. Only the combined impedance of the object responsible for the short, the wiring, and the transformer limits the fault current.

One objective of electrical distribution system design is to minimize the effect of a fault, i.e. its extent and duration, on the uninterrupted part of the system. Coordinating the sizes of circuit breakers and fuses assures that these devices isolate only the affected circuits. Put simply, it prevents a short at one location from shutting down power to the entire building.

Calculating the magnitude of short-circuit current is a prerequisite to selecting the appropriate breakers and fuses. If the distance between the transformer and starter is short, the calculation can be simplified by ignoring the impedance of the interconnecting wiring… a simplification that errs on the side of safety. One can also assume that the source of the fault has zero impedance, i.e. a

“bolted” short. Given these assumptions, only the transformer impedance remains. (Impedance upstream of the transformer is usually negligible.)

Suppose a 1,500-kVA, 480-volt transformer has impedance of 5.75 percent. With this value, use the equation below to determine how much fault current a short circuit will produce.The resulting I sc shows that a short would force the wiring to carry more than 30,000 amps when it was designed to handle only 400 amps!

49



50

I

SC

=

1,500 kVA x 1000/k

480 V x 1.73 x 0.0575

I

SC

= 31,400 amps

Short-circuit current is often two orders of magnitude greater than normal operating current.

Unless a circuit breaker or fuse successfully interrupts the fault, this enormous amperage rapidly heats components to very high temperatures that destroy insulation, melt metal, start fires … even cause an explosion if arcing occurs or components disintegrate.The inherent likelihood of severe equipment and property damage, as well as the risk of personal injury or death, underscores the importance of sufficient electrical-distribution system protection.

Ampere-Interrupt Current (AIC)

Determined under standard conditions, the “interrupt rating” specifies the maximum amount of current a protective device can cut off safely … i.e. without harm to personnel or resulting damage to equipment, the premises or the device itself. For example, a circuit breaker that trips “safely” successfully interrupts the fault, can be reset, and will function properly afterward.

A common misconception is, “An overcurrent protection device with a comparatively highinterrupt rating limits current to other components.” Not so, not unless it is also a true currentlimiting device. Even though the device successfully breaks the circuit, all components in the circuit will be exposed to the full magnitude of fault current (as well as the severe thermal and magnetic stresses that accompany it) for the small amount time it takes the device to respond.

Short-Circuit Current Rating (SCCR)

Sometimes referred to as the short-circuit withstand rating (SCWR), the short-circuit current rating

(SCCR) is probably the most critical rating for short-circuit protection that the electrical engineer must obtain from the starter supplier.The term “withstand” is no longer used by NEC and UL.The

entire assembled starter enclosure has an SCCR.

The short-circuit current rating is the maximum fault current that the starter withstood during testing by Underwriters Laboratories, Inc. UL 508 defines the short-circuit test methods and parameters for HVAC equipment, and therefore the SCCR is mainly a low-voltage issue. Essentially, the test simulates an actual fault current in the starter enclosure, e.g. 50,000 amps. If the doors blow open or if the starter emits debris, the enclosure fails the test. For those that pass, it is “acceptable,” and even probable, that the internal components will be damaged beyond repair. Given the destructiveness and expense of this test, it is not surprising that most manufacturers prefer not to pursue higher-than-normal short-circuit current ratings for their equipment unless there is a documented need.

Recall that when a fault occurs, all components in the circuit experience the brunt of the short circuit until it is interrupted. Therefore, it is important to assure that all components “at risk” can withstand a fault condition without causing personal injury or damaging the surroundings. The

National Electric Code (NEC) states this requirement in Section 110.10, “Circuit Impedance and

Other Characteristics”:

The overcurrent protective devices, the total impedance, the component short-circuit

[withstand] ratings, and other characteristics of the protected circuit shall be selected and coordinated to permit the used circuit protective devices to clear a fault without extensive damage to the circuit’s electrical components.This fault is assumed to be either between two or more of the circuit conductors, or between any circuit conductor and the grounding conductor or enclosing metal raceway. Listed products applied in accordance with their listing shall be considered to meet the requirements of this section.

Commentary in the 1996 National Electrical Code™ Handbook further explains Section 110.10:

CTV-PRB004-EN



Overcurrent protective devices (such as fuses and circuit breakers) should be selected to ensure that the short-circuit withstand rating of the system components will not be exceeded should a short circuit or high-level ground fault occur.

System components include wire, bus structures, switching, protection and disconnect devices, distribution equipment, etc., all of which have limited short-circuit current ratings and would be damaged or destroyed if these short-circuit current ratings are exceeded. Merely providing overcurrent protective devices with sufficient interrupting ratings will not ensure adequate short-circuit protection for the system components. When the available short-circuit current exceeds the withstand rating of an electrical component, the overcurrent protective device must limit the let-through energy to within the rating of that electrical component.

To comply with this section of NEC without additional current-limiting devices, most chiller-motor configurations will require a short-circuit current rating well above UL’s standard ratings.

Let-Through Current (LTC)

This is the fault current that passes through the circuit breaker before the circuit breaker trip element has time to respond, typically equal to or less than the available fault current and lasting three-quarter of an electrical cycle.

Current limiting

All components and wiring in an electrical distribution system offer some degree of resistance.

Under normal conditions, the heat produced when current flows against this resistance readily dissipates to the surroundings; however, the enormous current generated during a short circuit produces damaging heat at a much faster rate than can be safely dissipated. Interrupt the current and you stop adding heat to the system. As Figure 38 suggests, time is a critical determinant of the amount of heat (energy) added. An electrical short that lasts three cycles, for example, adds six times the energy of an electrical short lasting just one-half cycle. It is in this sense that all circuit breakers and fuses “limit” current.

Figure 38 also shows the effect of a current-limiting device. To be truly current limiting, the interrupting device must open the circuit within one-quarter cycle (1/240 second), i.e. before the fault current peaks.

Figure 38. Illustration of short-circuit current

100,000

Prospective available short-circuit current that would flow when a fuse is not used.

CTV-PRB004-EN

Current

10,000

0 t c

Peak Fuse

“Let-Thru”

Current

Total Fuse Clearing Time

Time

51


Electrical System—Design Guidelines

Figure 39. Electrical rating label locations

AFC—available fault current

Three-phase line power

SCCR—starter short-circuit current rating

AIC—circuit breaker ampere-interrupting rating

Starter door

There are three functions that electrical engineers must address when designing electrical systems that include chiller motors and the associated starters:

1.

Means of disconnect

2. Means for short circuit interruption

3. Making sure that the starter enclosure has an adequate short-circuit current rating for the available fault current (low voltage) or properly sized fuses (medium voltage)

Disconnect Means

Low-voltage disconnect

Low-voltage starters from Trane do not have a disconnect means as standard. The standard line power connection is a terminal block (i.e., main lug only) connection. An optional non-fused disconnect switch, in a molded case as shown in Figure 40 , can be installed. These non-fused disconnect switches typically have locking provisions to allow the switch to be locked open; often with up to three different padlocks.

Figure 40. Non-fused disconnect

52

A non-fused disconnect switch is used when servicing the chiller to protect someone from personal injury, and it can also be used as a load-break switch in an emergency. Since the disconnect switch is a non-fused device, current limiting protection must be installed upstream of the chiller by others.

CTV-PRB004-EN



Medium-voltage disconnect

All medium-voltage starters have an isolation switch as standard.This switch is a non-load-break switch that is not designed to be opened under load, i.e. while the chiller is operating. All mediumvoltage starters have a mechanical interlock to prevent opening the isolation switch while the main contactor is closed and the compressor is running.

In order to open the medium-voltage compartment door, the compressor must be turned off before the isolation switch can be opened. Then the isolation switch stabs can be separated from the medium-voltage bus. Baffles slide over the stab slots and the medium-voltage bus is completely isolated behind shielding panels. Now the medium-voltage compartment door can be opened safely. After servicing, the medium-voltage compartment door must be secured before the isolation switch can be closed.

Figure 41. Isolation switch incoming line power

Figure 42. Load-break switch incoming line power load-break switch section

X-Line starter

Low

Volts isolation switch load-break switch

Low

Volts isolation switch outgoing load power outgoing load power

If there is a requirement to be able to open the circuit while under load, a load-break disconnect switch may be furnished as a special option on medium-voltage starters.The load-break switch is mounted in an additional section of the starter-cabinet assembly. See Figure 41 and Figure 42 for a comparison of the two options. A switch spring is loaded, or “charged,” as the handle is moved.

When spring pressure is sufficient, a device releases the switch mechanism. The spring loading provides a rapid, positive opening and closing of the contacts.

Note: Medium-voltage circuit breakers are not available through Trane.

Short-Circuit Interruption

Low-voltage short-circuit interruption

When a circuit breaker is specified, it serves both as the short-circuit interrupt protector and the disconnect switch. Unlike the non-fused disconnect, a circuit breaker does have an interrupting rating. Because a circuit breaker is constructed to safely interrupt the high level of current caused

CTV-PRB004-EN 53


Electrical System—Design Guidelines by a short circuit (fault current), it may be opened safely at any time. A low-voltage starter door may be opened only if the circuit breaker is in the “off” or open position.

Circuit breakers of various interrupt ratings are offered as options. The interrupting capacity of a circuit breaker must also be considered. An analysis of an installation is usually done by the electrical engineer to calculate the maximum available fault current (AFC) that could be delivered if a short circuit occurred.

When a low-voltage starter is ordered with a circuit breaker, the starter manufacturer furnishes a standard circuit breaker sized at approximately 125 percent of compressor RLA or larger.The trip current of a circuit breaker is adjustable so that it will not trip during starting and acceleration, but will trip instantaneously (typically within one cycle) if a short circuit occurs.

Short-Circuit Current Rating (SCCR)

The disconnect means and the short-circuit protection discussed above are either supplied and installed by the customer upstream of the starter or they can be supplied as options with theTrane ® starter. However, the starter’s SCCR must be communicated to the electrical engineer early in the project to ensure that the starter short-circuit current rating will meet the requirements. If the SCCR is not high enough, the electrical engineer will have to look for solutions upstream of the starter.

Each low-voltageTrane ® starter or frequency drive has a short-circuit current rating, based on the size of the starter as well as the type of disconnect or circuit breaker included. See the appropriate submittal drawings for the starter short-circuit current rating.

Note: Don’t confuse short-circuit current rating (SCCR) with silicone controlled rectifier (SCR)— utilized in solid-state starters and AFDs.

Medium-voltage short circuit interruption

All medium-voltage starters contain current-limiting fuses for short circuit protection.The currentlimiting fuses and isolation switch, which is furnished as standard, fulfill the request for a fused disconnect. If you need more detail on the fuses for a particular starter contact CenTraVac Field

Sales Support.

It turns out that the starter short-circuit current rating is not an issue with medium-voltage starters.

Because Trane ® medium-voltage starters meet UL 347, current-limiting power fuses are required and provided as standard, and the starter short-circuit current rating no longer applies. Mediumvoltage starters fromTrane have an interrupt rating based on the standard current-limiting fuses.

At 4,160 volts, the NEMA E2 fused-interrupt rating is 50,000 amperes or 400 MVA.

Medium voltage fuse coordination suggestions

Proper sizing of fuses and circuit breakers upstream of the starter is the responsibility of the customer or the electrical engineer.

Power Circuit Requirements

Starter Applications

When applying a starter to a chiller motor on a specified power circuit, the power circuit has to meet minimum criteria to allow for a successful chiller start without an immediate shutdown or safety trip.This applies to utility power, local or smaller-scale facility power, and backup or peak-shaving generator power.

The following are some considerations for motor starter power quality requirements:

• Size of the power circuit

• Source and/or total system impedance

• System regulation

• Inrush characteristics of the starter type

• Acceleration time

• Maximum voltage sag

• Maximum voltage swell

54 CTV-PRB004-EN


CTV-PRB004-EN


• Additional (non-chiller) loads on the power circuit

When evaluating a power system for a chiller-compressor motor with a specified starter type, calculations must be done in order to size or “correct” the power circuit properly in order to successfully start the motor and keep the motor-starter combination online during operation.

Table 9 and Table 10, p. 55 show specific starter characteristics and minimum power requirements.

Table 9.

Sizing requirements

Starter Type Voltage Range

Inrush

Current

% LRA

Chiller Controller

Maximum Acceleration

Time Setpoint (sec) (a)

Percent

Rated

Torque

Wye-Delta

Solid-State

X-Line

Primary Reactor

208–600 V

208–600 V

2.3–13.8 kV

2.3–13.8 kV

33

~45

100

65

27

27

6

16

33

33

100

42

Autotransformer

AFD

2.3–13.8 kV

460–600 V

45

<13

16

12

42

Varies

(a) The Chiller Controller Maximum Acceleration Time Setpoint is the maximum allowable acceleration time; if the chiller has not started within this time, a diagnostic will be set.

Table 10. Motor starter operational voltage range—during a start

Starter Size

155–606 amps

607–1,316 amps

607–1,856 amps

185–1,120 amps

180–960 amps

961–1,600 amps

155–1530 amps

Starter Description

Unit- and Remote-Mounted

Wye-Delta

Unit-Mounted

Wye-Delta

Remote-Mounted

Wye-Delta


Solid-State

Remote-Mounted,

High-Fault Solid-State

Remote-Mounted,

High-Fault Wye-Delta


Low Voltage AFD

Maximum

Line-to-Line

RMS Voltage Sag

25%

25%

20%

25%

25%

25%

25%

Maximum

Line-to-Line

RMS Voltage Swell

15%

15%

15%

15%

15%

15%

10%

94, 187, 205/288 amps

(205 reduced voltage, 288 full voltage)

Unit-Mounted

Medium Voltage

(2.3–6.6 kV)

94, 187, 360 amps

94 amps

61–250 amps @ 4,160 V

Remote-Mounted

Medium Voltage

(2.3–6.6 kV)

Remote-Mounted

Medium Voltage

(10–13.8 kV)

Remote Medium-Voltage AFD

25%

(20% w/additional protection)

25%


25%


25%

15%

15%

15%

10%

Note: The maximum allowable under/overvoltage during normal operation is ±10 percent.

55


Electrical System–Power Wire Sizing

This section provides guidance for sizing the power conductors forTrane CenTraVac water chillers including wiring from the distribution system to the starter, and wiring from the starter to the compressor motor. The information provided does not constitute a design manual and does not supersede local code requirements or National Electric Code (NEC) recommendations. Final wire size selection must be verified by the Engineer of Record for the installation.

Wire size and count should be coordinated with the starter selection so the starter can be ordered with the proper terminal lugs. The starter is shipped with standard lugs as shown on the as-built submittals. Alternate lugs are often available and can be purchased locally. Standard lugs accept a wide range of wire sizes, but not all possible combinations.

General wiring requirements

• When more than one lead per phase is used (paralleled conductors), the leads must be of the same size and length so that they share the load equally. Paralleled conductors are only permitted for wire sizes of 1/0 and larger.

• When two or more conduits are used, all three phases must be equally represented in each conduit to avoid overheating.

Specific requirements for distribution system to starter wiring

• Wiring to the starter must be copper. A discussion of why aluminum should not be used can be found in the Glossary ( “Aluminum conductors,” p. 73 ).

• Wiring to all starters must be in multiples of three.

Specific requirements for starter to motor wiring

• All wiring to the CenTraVac motor must be copper. The UL listing on the CenTraVac requires copper conductors, and the terminal blocks on the motor studs are only compatible with copper wire.

• Wiring to motors used with variable frequency drive, across-the-line, autotransformer, or primary reactor starters must be in multiples of three. Wire for these starters is sized following the procedure used for sizing supply wire from the distribution system to the starter.

• Wiring to motors used with wye-delta (also referred to as star-delta) or inside-the-delta solidstate starters must be in multiples of six.The solid-state starter wire sizing tables included here are only applicable to the inside-the-delta solid-state starter designs offered for CenTraVac chillers shipped since June 1999. All other solid-state starter designs should follow the acrossthe-line wire sizing tables.

• A minimum of three feet of flexible conduit is required at the connection to the motor junction box to provide vibration isolation.

Wire size guidelines

The following information is based on the 2011 National Electric Code (NEC). Most local codes are based on the NEC; however, local codes may vary from the NEC on specific details. Final wire size selection must be verified by the Engineer of Record for the installation.

Various factors are involved in selecting the proper wire including amperage draw of the load, type of load, voltage, temperature rating of the wire, number of conductors within a conduit, and ambient temperature. In addition, the wires connecting the starter to the motor may need to be sized differently than the wires that connect the distribution system to the starter.

Good circuit design also involves checking the voltage drop of the distribution circuit.The NEC does not require this step, but does suggest that 3 percent voltage drop on a branch circuit feeder and

5 percent overall will provide “reasonable efficiency of operation”.

The NEC requires HVAC manufacturers to calculate and include “minimum supply circuit conductor ampacity” (also referred to as Minimum Circuit Ampacity [MCA]) on the unit name plate

(section 440.4 [B]). MCA is equal to 1.25 times the RLA of the largest motor plus 100 percent of all

56 CTV-PRB004-EN


Electrical System–Power Wire Sizing other electrical loads. Branch circuit wires supplying the unit must have an ampacity greater than the MCA.

Table 11, p. 58 through Table 16, p. 60 are based on the 2011 NEC conductor ampacities tables for copper wire, run in conduit, in air, for several common wire types and configurations. Where required by the NEC the values in the tables have been adjusted for more than three wires in a conduit.

Table 11, p. 58 through Table 14, p. 59 are for 0–2000 V applications where the ambient temperature around the conduit is between 78°F–86°F (26°C–30°C); Table 15, p. 60 and Table 16, p. 60 are for 2,001 V–35 kV applications where the ambient temperature around the conduits is

104°F (40°C) or less. Installations with ambient temperatures outside these ranges require an additional ampacity adjustment for proper wire selection.

The tables provide an easy way to estimate wire size. Enter the appropriate table, knowing the nameplate MCA of the chiller; a table value greater than the MCA indicates a valid wire/conduit selection (for the conditions described earlier in this section).

Example

The example chiller has a remote-mounted wye-delta starter and the nameplate indicates an RLA of 300 and an MCA of 384 at 460 volts.

If 75°C conductors are used, the supply leads from the distribution system to the starter are sized using Table 11, p. 58 . Comparing the MCA to the table values indicates the conductors could be any of the following combinations:

• one conduit containing three 600 MCM conductors

• one conduit containing six 250 MCM conductors

• two conduits containing three 3/0 conductors each, and so on

Because this is a wye-delta starter the leads from the starter to the motor are sized differently than the supply leads to the starter. If 75°C conductors are used the leads from the starter to the motor are sized using Table 12, p. 58 . Comparing the MCA to the table indicates the following combinations are allowed:

• one conduit containing six 300 MCM conductors

• two conduits containing three 4/0 conductors each

• two conduits containing six 1/0 conductors each

Conductor ampacity tables

The wire selection tables ( Table 11, p. 58 through Table 16, p. 60 ) may be used for estimating conductor and conduit combinations that will support the amperage draw of CenTraVac chillers.

Wire sizes are given in units of AWG (American wire gauge) or kcmil (thousands of circular mils), also referred to as MCM or KCM.

Find the appropriate table based on voltage, wire temperature rating, and where the wire will be used. A table value greater than the nameplate MCA indicates a valid wire/conduit selection (for the conditions described earlier in this section). Then check that the selected combination will fit in the starter lugs by reviewing the starter submittal data. Final wire size selection must be confirmed by the Engineer of Record for the installation.

CTV-PRB004-EN 57



Table 11. MCA look-up table for 75°C copper conductors rated for 0–2,000 Volts (a)

Note: Use this table to select supply leads for all starters, and motor leads for remote-mounted across-theline, primary reactor, autotransformer, and Adaptive Frequency Drives. Value in table must be larger than the MCA to use the wire combination.

Wire Size

8

1 Conduit

3 Wires

50

1 Conduit

6 Wires

1

0

00

000

3

2

6

4

65

85

100

115

130

150

175

200

0000

250

300

350

230

255

285

310

400

500

335

380

536

608

600 420 672

(a) Based on 2011 NEC Table 310.15(B)(16)

240

280

320

368

408

456

496

2 Conduits

3 Wires ea.

300

350

400

460

510

570

620

670

760

840

3 Conduits

3 Wires ea.

450

525

600

690

765

855

930

1005

1140

1260

2 Conduits

6 Wires ea.

480

560

640

736

816

912

992

1072

1216

1344

4 Conduits

3 Wires ea.

600

700

800

920

1020

1140

1240

1340

1520

1680

5 Conduits

3 Wires ea.

750

875

1000

1150

1275

1425

1550

1675

1900

2100

6 Conduits

3 Wires ea.

900

1050

1200

1380

1530

1710

1860

2010

2280

2520


Note: Use this table to select motor leads for remote-mounted wye-delta and solidstate starters (inside-the-delta designs only).Value in table must be larger than the MCA to use the wire combination.

Wire Size

8

1 Conduit

6 Wires

69

2 Conduits

3 Wires ea.

86

1

0

00

000

3

2

6

4

179

206

241

275

89

117

137

158

0000

250

300

350

317

351

393

427

396

439

491

534

400

500

462

524

577

655

600 579 724


224

258

301

344

112

146

172

198

2 Conduits

6 Wires ea.

413

482

551

634

703

786

855

924

1048

1158

4 Conduits

3 Wires ea.

517

603

689

793

879

982

1069

1155

1310

1448

3 Conduits

6 Wires ea.

620

724

827

951

1055

1179

1282

1386

1572

1737

6 Conduits

3 Wires ea.

775

905

1034

1189

1319

1474

1603

1732

1965

2172

58 CTV-PRB004-EN




Wire Size

1 Conduit

3 Wires

1 Conduit

6 Wires

2 Conduits

3 Wires ea.

3 Conduits

3 Wires ea.

2 Conduits

6 Wires ea.

4 Conduits

3 Wires ea.

5 Conduits

3 Wires ea.

6 Conduits

3 Wires ea.

4

3

8

6

55

75

95

115

2

1

0

00

000

0000

250

300

350

400

500

600

130

145

170

195

225

260

290

320

350

380

430

475

272

312

360

416

464

512

560

608

688

760

340

390

450

520

580

640

700

760

860

950

510

585

675

780

870

960

1050

1140

1290

1425

544

624

720

832

928

1024

1120

1216

1376

1520

680

780

900

1040

1160

1280

1400

1520

1720

1900

850

975

1125

1300

1450

1600

1750

1900

2150

2375

1020

1170

1350

1560

1740

1920

2100

2280

2580

2850

Note:

Use this table to select supply leads for all starters and motor leads for remote-mounted across-the-line, primary reactor, autotransformer, and

Adaptive Frequency Drives. Value in table must be larger than the MCA to use the wire combination.

(a) , Based on 2011 NEC Table 310.15(B)(16)


Wire Size

8

1 Conduit

6 Wires

75

2 Conduits

3 Wires ea.

94

2 Conduits

6 Wires ea.

4 Conduits

3 Wires ea.

3 Conduits

6 Wires ea.

6 Conduits

3 Wires ea.

1

0

00

000

3

2

6

4

0000

250

300

350

103

131

158

179

200

234

269

310

358

400

441

482

129

163

198

224

250

293

336

387

448

500

551

603

469

537

620

717

800

882

965

586

672

775

896

1000

1103

1206

703

806

931

1075

1200

1324

1448

879

1008

1163

1344

1500

1655

1810

400

500

524

593

655

741

600 655 819 1310 1637 1965 2456

Note:

Use this table to size motor leads from remote-mounted wye-delta and solid-state starters (inside-the-delta designs only). Value in table must be larger than the MCA to use the wire combination.


1048

1186

1310

1482

1572

1779

1965

2224

CTV-PRB004-EN 59



Table 15. MCA look-up table for 90°C copper conductors rated for 2,001–5,000 Volts (a)

Wire Size

1 Conduit

3 Wires

2 Conduits

3 Wires ea.

3 Conduits

3 Wires ea.

1

0

00

000

4

2

8

6

155

180

205

240

55

75

97

130

360

410

480

540

615

720

0000

250

350

500

750

280

315

385

475

600

560

630

770

950

1200

840

945

1155

1425

1800

Note: Use this table to select line-side wiring to the starter and load-side wiring between the starter and the motor. Value in table must be larger than the MCA to use the wire combination.

(a) Based on 2011 NEC Table 310.60(C)(73)

Table 16. MCA look-up table for 90°C copper conductors rated for 5,001–35,000 Volts (a)

Wire size

1 Conduit

3 Wires

2 Conduits

3 Wires ea.

3 Conduits

3 Wires ea.

0

00

000

0000

2

1

6

4

195

225

260

295

83

110

150

170

390

450

520

590

585

675

780

885

250

350

500

750

330

395

480

585

660

790

960

1170

990

1185

1440

1755

Note:

Use this table to select line-side wiring to the starter and load-side wiring between the starter and the motor. Value in table must be larger than the MCA to use the wire combination.

(a) Based on 2011 NEC Table 310.60(C)(73)

60 CTV-PRB004-EN


Starter Options

Starter Options

Customers often look for methods to reduce the installed cost and space requirements associated with electrical equipment. In addition, they may have specific electrical distribution requirements and the starters must have the flexibility to address these needs.

Configured options

There are many starter options available for low- and medium-voltage starters.These include, but are not limited to:

• Power factor correction capacitors (208 through 4,160 volts, 60 Hz)

• Digital meters

• Surge protection/lightning arrestors

• Ground fault protection

• Enhanced Electrical Protection Package

These options are directly selectable in the order configuration system. The next section will explain several of them in greater detail.

Design specials

There are also many design-special starter options that can be offered by contacting CenTraVac

Field Sales Support. These include but are not limited to:

• Power factor correction capacitors (all 50 Hz, and 60 Hz from 4,800 to 6,600 volts)

• NEMA 12, NEMA 3R, or NEMA 4 enclosures, remote starters only

• Wattmeter

• Watt-hour meter, add for demand register and pulse initiator

• Watt transducer

• Current transducer

• Voltage transducer

• MP 3000 motor protection package

• Communications cards for meters/motor protection packages

• IQ Analyzer motor protection/metering package

• Emergency stop button

• Extra control relays

• Main bus sections including ground bus (typically for medium voltage)

• Load-break switch (medium voltage only), formerly referred to as an ADM (AMPGARD

Disconnect) switch

Multiple Starter Lineups (2,300–6,600 volts)

Side-by-side starters

Several design special options are available with remote-mounted medium-voltage starters.These

reduce the installed cost and space requirements associated with the electrical equipment or to comply with special electrical distribution requirements.

Figure 43, p. 62 shows two across-the-line starters “bussed” together.This option has a single line power feed for the starter “line-up.” Additional starters can be added to the lineup as long as each starter has the top-mounted main bus section. Each starter has its own load wires that will run out to the chillers.

CTV-PRB004-EN 61


Starter Options

Figure 43. Top-entry, multiple, across-the-line starter arrangement (2.3–6.6 kV) incoming line power

12"

18" pull box main bus

X- Line starter X- Line starter

80"

30"

72"

Bottom-entry line power

Figure 44, p. 63 shows the same concept as above; however, it uses what is called an auxiliary section that allows the customer to bring wires in from the bottom to power the main bus.

62 CTV-PRB004-EN


Starter Options

Figure 44. Bottom-entry, multiple, across-the-line starter arrangement (2.3–6.6 kV) main bus auxiliary section main bus

X- Line starter X- Line starter

92"

30"

24" 72" incoming line power

Multiple starter lineups for 10–13.8 kV starters

Side-by-side starter lineups are available for 10–13.8 kV starters. Contact CenTraVac Field Sales

Support for dimensions and availability.

Industrial-Grade Starters

High-fault starters can be selected independently of the Enhanced Electrical Protection Package.

High-fault, remote, solid-state starters (IHRS)

• NEMA 12



960 amps

• Flanged disconnect

• 100,000 amps short-circuit current rating

• SAE HS-1738

• Up to 600 volts

High-fault, remote, wye-delta starters (HRWD)

• NEMA 1,961 to 1,600 amps

• Non-flanged disconnect

• 85,000 amps short-circuit current rating

• Up to 480 volts

Medium-voltage remote starters (2,300–6,600 volts)

• Across-the-line, primary reactor, and autotransformer

• NEMA 12 option

• SAE HS-1738 option


CTV-PRB004-EN 63


Starter Options

Figure 45. High-fault wye-delta starter

Enhanced Electrical Protection Package

Applications that require the utmost reliability and rugged construction may prompt the selection of the Enhanced Electrical Protection Package. CenTraVac chillers equipped with the Enhanced

Electrical Protection Package are constructed to NEMA 4 guidelines and feature completely enclosed wiring in seal-tight conduits and junction boxes. The Enhanced Electrical Protection

Package control panel also includes some additional installation features and layout improvements. The purge is also upgraded to NEMA 4 construction. The entire chiller is siliconefriendly —all silicone is encapsulated and non-volatile so it does not affect any industrial and/or chemical processes.

Figure 46. CenTraVac with Enhanced Electrical Protection Package (AdaptiView unit controller)

64

Note: Unit shown with optional, unit-mounted control power transformer (below motor terminal box).

CTV-PRB004-EN


Starter Options

These and other features listed in the following section allow the CenTraVac to meet or exceed the rigorous criteria of the Society of Automotive Engineers “Standard for Electrical Equipment for

Automotive Industrial Machinery, 2002 Edition” (SAE HS-1738). HS-1738 provides requirements and recommendations relating to the electrical equipment of machines so as to promote:

• safety of persons and property

• consistency of control response

• ease of maintenance

Enhanced Electrical Protection Package Purge

• NEMA 4 construction

• Seal-tight conduits

• Sealed motor terminal box

• Totally Enclosed Fan Cooled (TEFC) pumpout motor

Enhanced Electrical Protection Package Control Panel

• NEMA 4 construction

• accessory port circuit breaker

• screw-type terminal block connections

• welded seam construction

CTV-PRB004-EN

Enhanced Electrical Protection Package Chiller Enhancements

• SAE HS-1738

• Warning markings

• Phenolic (permanent) labels on control devices

• Silicone-friendly to industrial processes—all utilized silicone is encapsulated and non-volatile

• Polycarbonate junction boxes listed NEMA 4X

65


Starter Options

66

Enhanced Protection (EPRO)

The Enhanced Electrical Protection Package includes the EPRO package, which includes sensors and transducers that enable the following chiller protection features:

Enhanced condenser-limit control.

Factory-installed condenser-pressure transducer with interconnecting piping and wiring provides enhanced high-pressure cutout avoidance by energizing a relay to initiate head relief.

Note: This protection is in addition to the standard high refrigerant-pressure safety contact.

Compressor-discharge refrigerant temperature protection.

Factory-installed sensor and safety cutout on high compressor-discharge temperature allows Tracer AdaptiView to monitor compressor discharge temperature and display the temperature at the chiller controller and at

Tracer Summit™.

Bearing oil temperatures.

Factory-installed sensors allow high-temperature safety cutouts to monitor the leaving bearing oil temperatures and display the temperatures at the chiller controller and at Tracer Summit.

The high bearing-temperature cutout is fixed at 180°F (82.2°C). If either bearing temperature violates the cutout, a latching (manual reset) diagnostic is generated.

Enhanced Electrical Protection Package Options

In addition to the above standard elements, customers who purchase the Enhanced Electrical

Protection Package have additional options. These options can be applied to remote-mounted medium-voltage starters, both from Trane and from other starter manufacturers.

CPTR, Control-Power Transformer (Enhanced Electrical Protection Package option).

4 kVA control-power transformer mounted on the chiller (480 to 115 volts)


• Fused primary and secondary power

• Secondary fuse status indictor (blown or not-blown)

• UL 508 Type 12 construction

• Unit-mounted and factory-wired

SMP, Supplemental Motor Protection—Medium voltage only (Enhanced Electrical

Protection Package option).

A separate enclosure mounted to the motor includes:

• Surge capacitors

• Lightning arrestors

• Zero-sequence ground fault

Other features:

• UL 347 tested Type 12 construction

• Field-accessible terminal block for trouble-shooting via panel

• Unit-mounted and factory-wired

CTV-PRB004-EN


Starter Options

When the SMP option is selected, the medium voltage starter must be remote.

Note: Additional “top hat” provisions may need to be field-supplied to allow for shielded cable with stress cones (field-provided).

DMP, Differential Motor Protection (selectable with the SMP option).

DMP replaces the zero-sequence ground fault protection. Instead, it uses a flux-summation, self-compensating differential protection scheme for a quicker and more precise removal of line power during a fault

(see “Differential motor protection,” p. 75 ).

Note: DMP is available only for 1,062 kW and larger motor sizes up to 5,000 volts.

Figure 47. Supplemental motor protection enclosure with DMP option

1

CTV-PRB004-EN

2 3

1.

Lightning arrestors

2. Surge capacitors

3. SEPAM module (Square D Electrical Protection and Metering)

Implications of the Enhanced Electrical Protection Package and SMP option on customer-supplied starters (SBO).

Most of the accommodations that would need to be met by the customer who wishes to use a non-Trane starter are provided with the Enhanced Electrical

Protection Package and the SMP option.

Note: Trane-supplied starters already include these items.

The supplemental motor-protection enclosure will include:

• Primary, single-stage current transformer in lieu of primary and secondary CTs

The oversized control panel will include:

• Second-stage PTs, 115 to 30 volts, for medium-voltage applications only

• Three-pole disconnect

• Industrial terminal block for field control and control-power connections

67


Starter Options

68

The customer is still responsible for providing primary potential transformers for medium voltage.

Criteria for the Enhanced Electrical Protection Package.

The Enhanced Electrical Protection

Package may be selected for CenTraVac chillers that meet the following criteria:

• Single compressor (no Duplex™)

• 60 Hz only

• 080, 142, 210, and 250 shells in all short, long, and extended combinations

• Motor frame sizes 440E, 5000, 5800, and 5800L, which correspond to approximate chiller capacities from 450 to 2,000 tons

• NEMA 1 unit-mounted starters can be accommodated. Contact CenTraVac Field Sales Support for details.

Refer to CTV-PRC007-EN ( Product Catalog: EarthWise™ CenTraVac™Water-Cooled Liquid Chillers ) for information on possible special configurations.

Note: Placing a unit-mounted starter on an chiller equipped with the Enhanced Electrical

Protection Package negates the chiller’s NEMA 4 rating and changes it back to a standard

NEMA 1 rating.

Industrial paint.

Trane offers a two component, catalyzed, executive beige high-solids epoxy coating paint system to meet or exceed the performance of the US Department of Defense

(USDOD) military specification MIL-PRF-22750F.This paint has a volatile organic compound (VOC) content less than 2.8 lb/gal (335.6 g/L). It offers protection and resistance to fluids, adhesives, solvents, heat, and weather. We recommend that it be used with the “Enhanced Electrical

Protection Package,” p. 64 ; it is priced separately.

Starters by Other Manufacturers (SBO)

Occasionally a customer chooses to reuse an existing starter or purchase a starter directly from a starter manufacturer. While this can be accommodated, it requires careful coordination between theTrane sales representative and the owner, engineer, and starter manufacturer because generic or existing starters are not compatible with the Trane ® chiller control panel.

Non-Trane starters must be modified with the proper components and control wiring before they are connected to a Trane ® chiller. Existing starters should be modified by the owner’s representative; new starters should modified by the starter manufacturer. Trane assumes no responsibility for the design, construction, compatibility, installation, startup, long-term support, and will not maintain records or drawings for the resulting starter.

Trane provides a Starter by Others specification, which provides the information required for others to build a starter that is compatible withTrane ® centrifugal compressor motors and controls.

When a non-Trane-provided starter is used, it must be modified to conform to the appropriateTrane

Starter by Others specification. SBO specifications are revised on a regular basis, so it is important to obtain the correct version before building or modifying a starter by others.

It is also important to include the cost of conversion when determining the total cost of a non-Trane starter; therefore, the owner should be provided with the appropriate SBO specification before the decision is made to reuse or purchase a non-Trane starter. Components required for conversion include but are not limited to:

• 4 kVA control-power transformer (1)

• Primary current transformers (3)

• Secondary current transformers (3)

• Primary potential transformer (1) for medium-voltage starters

• Secondary potential transformers (3) for medium-voltage starters

• Other optional starter equipment, e.g. power factor correction capacitors, as required by the specification

TheTrane ® chiller control panel integrates the chiller, motor, and starter into a single control and protection system. Therefore, non-Trane starters do not require an additional motor-starter protection package. If a non-Trane starter includes a protection package, the protection package

CTV-PRB004-EN


Starter Options must be disabled or the sensitivity of all the starter trip levels must be readjusted so that theTrane ® control panel acts as the primary protection for both the chiller and the starter.

Chillers used with non-Trane starters must ship with a special control panel to accommodate the non-Trane starter. It is the responsibility of theTrane sales representative to select the “Starter by

Others (SBO)” option when pricing the chiller and to assure that the non-Trane starter is built according to the proper “Starter by Others” specification.

Note: The Enhanced Electrical Protection Package can simplify the procedure for using a non-

Trane starter; see “ Implications of the Enhanced Electrical Protection Package and SMP option on customer-supplied starters (SBO) ,” p. 67 .

In summary, when a customer wants to buy a starter from a manufacturer other than Eaton Cutler-

Hammer ® , the procedure is as follows:

1.

Price the appropriate customer-supplied starter.

2. Provide a copy of the “Starter by Others” (SBO) specification S6516-0513 from CenTraVac Field

Sales Support to the customer/starter manufacturer. This specification lists the allowable starter types.

3. Inform the customer that Trane assumes no responsibility for the design, construction, compatibility, installation, startup, long-term support, and will not maintain records or drawings for the resulting starter.

Power Factor and CenTraVac Chiller Motors

CenTraVac squirrel-cage induction motors normally have an uncorrected full-load power factor of

88 to 92 percent.The power factor decreases slowly as the motor’s torque output drops from full load to approximately 50 percent, and then falls more rapidly at lower loads. If the full-load power factor is corrected to 95 percent, the entire curve shifts upward and the corrected power factor remains at a high value ( Figure 48, p. 70 ).The current (amps) for a motor with a corrected power factor is lower than the current for a motor with an uncorrected power factor.

In some cases, a power factor greater than 95 percent is specified for “all load ratios above

40 percent” or at a particular operating point. Multiple-capacitor arrangements with an elaborate switching mechanism can provide this level of correction without overcorrecting by “cycling” various capacitor combinations on and off as motor loading dictates; however, this arrangement is complex and its cost may be prohibitive.

Typically, specifications stipulate a corrected power factor of 95 percent at full load.This results in an economical application that balances the first cost of the capacitors with the benefits of a higher power factor.

Several equations are helpful:

ApparentPower(kVA) =

ActualPower(kW)

PowerFactor

=

Volts x Amps x



3

1000

ActualPower(kW) =

Volts x Amps x



3 x PF

1000

CTV-PRB004-EN 69


Starter Options

Figure 48. Typical CenTraVac chiller-motor power factor

70

PFCC Placement and Sizing.

PFCCs may be installed at various locations in the power supply network. Utility companies install capacitor banks on their distribution feeders and substation buses. These capacitors correct for the utility’s reactive loads and for other large reactive loads, such as those found in business or industrial areas.

When utility customers correct for the reactive loads in their facilities, they usually install PFCCs at the facility’s electrical service entrance or at the individual loads within the facility. Connecting the PFCCs at the service entrance corrects reactive loads throughout the facility.This strategy can be advantageous if the facility contains a large number of small reactive loads—but it can also be costly. Successful implementation requires expensive hardware to monitor the power factor as loads are added to and removed from the distribution system, then switch capacitors on- and offline accordingly.To avoid this expense, PFCCs are most commonly installed near each piece of switchgear that supplies a reactive load.

Engineering Toolbox.

Trane has a program called Engineering Toolbox, available online or throughTrane Desktop Manager, that can be used to calculate the kilovolt-amperes reactive (kVAR) of correction needed. Toolbox can calculate kVAR using information from the motor data sheets without adjustments at 60 and 50 Hz. Contact yourTrane sales representative for more information.

PFCC Application Guidelines.

Three “rules” govern the application of capacitors dedicated to a specific reactive load and its switchgear:

• “Rule 1”—Simultaneously disconnect capacitors and load from line power

• “Rule 2”—Size motor overload protection to account for capacitor-supplied current

• “Rule 3”—Accurately size PFCCs that remain connected to the motor when it is offline

These guidelines are explained on the following pages.

Rule 1— Simultaneously disconnect capacitors and load from line power.

If the capacitors are not switched offline when the load is disconnected, they continue to add capacitance to the electrical distribution system. A “leading” power factor—too much capacitance may eventually develop. This overcorrection causes poor voltage regulation, i.e., voltage is high when the circuit is unloaded, then drops as loads are added.

Rule 2— Size motor overload protection to account for capacitor-supplied current.

Overloads are typically set to measure the total current drawn by the motor.When PFCCs are used, they become another source for a part of that current. If the current they provide is not “seen” by the overload protectors, potentially damaging amperage can reach the motor. The simplest way to ensure that the overloads “see” all current supplied to the motor is to position the PFCCs upstream of the overloads as shown in Figure 49 .

CTV-PRB004-EN


Starter Options

Figure 49. PFCCs installed downstream of starter contactor, upstream of overloads

Power

Circuit

1

2

3

Motor Starter

Contactor

Overload

Protectors

Motor

Fusible

Safety Switch or

Suitable Breaker

Enclosed

Capacitor Unit

3-Phase

Capacitor

Fuses

If the capacitor connection points are downstream of the overload devices, route the PFCC leads through the overloads as shown in Figure 50, p. 71 .This assures that the overloads register both line- and capacitor-supplied current.

Figure 50. PFCC wires routed through overload protectors

1

2

3

Power

Circuit

Fusible

Safety Switch or

Suitable Breaker Overload

Protectors

Motor

Starter

Contactor

Enclosed

Capacitor Unit

Fuses

3-Phase

Capacitor

Motor

Rule 3— Accurately size PFCCs that remain connected to the motor when it is offline.

Connecting PFCCs to the load side of the motor-starter contactor is commonly used as a simple, low-cost way to comply with “Rule 1.” However, the motor may be damaged if the PFCCs are too large. As a “rule of thumb,” the maximum corrected power factor is 95 percent for a CenTraVac chiller motor operating at full load.

Failure to comply with this rule can cause significant damage due to voltage regeneration. The manufacturers of CenTraVac chiller motors place maximum limits on both the corrected power factor and the capacitor size. PFCCs that remain connected to the motor when it is offline must not exceed the motor manufacturer’s maximum limit.

CTV-PRB004-EN 71


Starter Options

Figure 51. PFCCs with separately controlled motor contactor

1

2

3

Power

Circuit

Fusible

Safety Switch or

Suitable Breaker

Overload

Protectors

Fuses

Motor

PR Motor Starter

Contactor or

Silicon-Controlled

Rectifiers (SCRs)

C

Enclosed 3-Phase

Capacitor Unit

Line-side PFCC placement.

Figure 51 , depicts an arrangement that provides an alternative to installing capacitors downstream of the motor-starter contactor. While this configuration can be used with any type of starter, it is mandatory for all solid-state starters.

Notice that the PFCCs are connected to the line side of the main contactor (or other switching device) via a separately controlled contactor.This separate contactor is governed by a pilot relay (PR) at/in the motor-starter contactor or silicon controlled rectifiers (SCRs, solid-state starter applications) to switch the capacitors on- and offline with the load.

By connecting the PFCCs through a separate contactor they do not remain connected to the motor or the line when the motor is disconnected.This configuration prevents voltage-feedback problems and can be used for cases where correction beyond 95 percent is desirable. Correction beyond the manufacturer’s maximum limit should not be done without consulting the manufacturer regarding the application.

If the PFCC connections are downstream of the overloads, the capacitor leads must be routed through the overloads as Figure 51, p. 72 illustrates. Notice that the capacitors are not connected to the motor when it is disconnected from the line. This prevents the “motor-generated voltage buildup” described in “Rule 3”, p. 71 .

72 CTV-PRB004-EN


Glossary

A

Acceleration time

The time it takes a motor to reach full design speed from the moment power is applied. Typical CenTraVac motor acceleration times associated with various starter types are listed in Table 5, p. 17 (low voltage) and Table 7, p. 31

(medium voltage).

Advanced motor protection system

Standard motor protection provided by the CenTraVac microprocessor-based control panel. By monitoring current and voltage in each of the three motor power phases, the panel provides protection throughout the motor starting and running modes from the adverse effects of phase imbalance, phase failure, phase reversal, overvoltage, undervoltage, and electrical distribution fault

(momentary power loss). Sensing any of these faults, the panel trips-out the motor instantaneously and provides a diagnostic display. The chiller controller also protects

“adaptively” for overcurrent. By reducing the load, it may be able to avoid a shutting down the chiller once it reaches the current limit.

Automatic restart is provided after restoration of power when the stoppage is caused by distribution fault or extended power loss.

Air break

Contacts exposed to open air that rely on an air gap to keep an electrical circuit open. Air break contactors are an obsolete technology that has been replaced by vacuum break contactors. See “Vacuum break,” p. 81 .

Aluminum conductors

Trane requires that power wiring to the motor use copper conductors. Aluminum conductors are not suitable for the following reasons:

•UL requirements

•Galvanic corrosion

•Higher probability of connection failure

•Terminal block design

Galvanic corrosion occurs when air and moisture are present at an aluminum-copper connection. The resulting electrolysis process causes the loss of aluminum at the interface of the dissimilar metals.

Another reason to use copper conductors is the decreased probability of connection failure . Aluminum connections require greater care at initial installation as well as periodic maintenance and inspection because of oxidation, torque requirements, cold flow, and thermal expansion coefficients .

Greater care in connecting aluminum wire is required since an aluminum oxide film must be removed or penetrated before a reliable aluminum joint can be made.

This oxide film insulates the aluminum and increases joint resistance.

Torque requirements are critical when aluminum connections are made. It is difficult to ensure that these requirements will be met at the time of installation.

Cold flow or “creep” results because aluminum has a lower modulus of elasticity than copper and tends to creep away from a stressed area when under pressure.

The resulting loosened connection can increase joint resistance and lead to failure of the connection. Periodic maintenance and inspection is required to assure good connections.

Aluminum and copper have different thermal expansion coefficients . Aluminum expands 36 percent more than copper under thermal cycling. When the terminals and connections are subjected to a large temperature change, a gap may open between the aluminum cable and the copper lug. This, combined with cold flow, can result in a very high resistance joint and lead to failure of the connection.

The final reason to use copper conductors is terminal block design . Because aluminum electrical conductivity is about 60 percent that of copper, larger aluminum cables are required to conduct the same amount of current.

These larger cable sizes may not fit terminals designed for copper. It is also possible that the block itself may not be suitable for use with aluminum wire as determined by the block manufacturer.

Amps, motor full-load amps (FLA)

FLA is the amperage the motor would draw if it was loaded to its full rated capacity, i.e. motor size kW. The

FLA is not available from the selection program; however, it can be obtained from CenTraVac Field Sales Support.

Amps, motor locked-rotor amps (LRA)

Once a motor has been selected, there is a specific locked rotor amperage value associated with the specific motor.

This is the current draw that would occur if a motor was running, and then the rotor shaft was instantaneously held stationary. LRA is typically 6–8 times that of the motor fullload amps (FLA). LRA is also used commonly in discussing different starter types and the amperages associated with the start.

CTV-PRB004-EN 73


Glossary

Amps, primary rated-load amps (RLA)

Commonly referred to as the selection RLA or the unit

RLA. This is the amperage that is drawn when the chiller is at full cooling capacity in terms of cooling tons (kW).

RLA is listed on the nameplate, and it is the key number used to size the starter, disconnects, circuit breakers, and

Adaptive Frequency Drives (AFD) for a typical chiller. It is also the value used to determine the minimum circuit ampacity (MCA) for sizing conductors. Primary RLA is always less than or equal to the motor full-load amps

(FLA).

Anti-recycle protection

A control method that limits the number of compressor starts within a given time period. Prior to 2000, the

CenTraVac was limited to one start every 30 minutes

(30 minutes from start-to-start).

Today, a more flexible protection system called restart inhibit is utilized. Typically several rapid restarts are allowed before a time limit is set. The time limit, if enforced due to several rapid restarts, is dependent on motor winding temperature, unit size, and an adjustable delay time constant.

This protection is a standard feature of the CenTraVac control panel.

Available fault current (AFC)

Electrical engineers usually calculate and design to a potential short-circuit current that originally comes from the utility power system. They call this term the available fault current because they take the potential fault current and then evaluate it via computer programs to determine an available fault current just upstream of the chiller starter or frequency drive. The starter short-circuit current rating should be greater than or equal to the available fault current to safely contain starter components should a short-circuit occur.

B

Bus

A bar of conductive material—usually copper—used to carry large electrical currents to supply multiple circuits or components. A bus is typically used to connect several medium-voltage starters together and thereby require only a single power connection for incoming line power.

C

California code

Available on CenTraVac chillers with low-voltage starters

(UL as standard) with disconnects or circuit breakers. Lowvoltage starters with terminal blocks require a special configuration which is available as a standard option in the order system. On medium voltage, the standard UL certification satisfies California Code requirements.

Circuit breaker

A device that protects a circuit by opening its contacts when a current responsive element senses overcurrent or short-circuit current. A circuit breaker protects electrical components from further damage if any one component within that system experiences a short circuit. Circuit breakers are used on low-voltage starters only. The overload function is not used; overload is accomplished by the chiller controller. Circuit breakers are sized based on the primary RLA from the nameplate, the required AIC of the breaker, and the required SCCR of the starter enclosure.

Contactor

A multi-pole relay whose contacts are rated to carry line current. The contactor connects and disconnects a motor to and from line power. The coil of a contactor may be operated by line voltage, control voltage, or through a rectifier (DC voltage).

Control-power transformer (CPT)

A device that reduces incoming line voltage to control voltage (i.e., 480 V to 120 V). The control-power transformer is usually located in the starter. A 4 kVA transformer is provided as standard in CenTraVac starters—3 kVA transformer provided with AFDs. The

Enhanced Electrical Protection Package provides an option to mount the CPT separately on the side of the chiller. This transformer takes care of the chiller’s auxiliary power needs such as the purge, oil pump, heater, etc.

Corona

A visible pale glow surrounding an insulated conductor typically carrying over 2000 volts. Ozone odor is present and the air around the wire becomes ionized. An increase in voltage may cause the corona effect of adjacent wires to increase until spark-over occurs. See “Stress cone

(stress relief cone),” p. 80 .

Current-limiting fuse

A current-limiting fuse is a fuse that recognizes the rate of current increase and will melt its element and open the circuit in less than one-quarter of an electrical cycle in the event of a short circuit. Thus, the total short-circuit current available never passes through the current-limiting fuse.

CenTraVac medium-voltage starters contain three currentlimiting fuses as standard.

74 CTV-PRB004-EN


Glossary

Current transformer

A device that produces a reduced current signal that is proportional to the primary current. A current transformer may resemble a square or round doughnut. Each motor lead passes through the center of a current transformer and a reduced proportional current signal is obtained at the current transformer leads. There is no direct electrical connection between the motor lead and the current transformer. The voltage in the output circuit of a current transformer will be whatever voltage is necessary to drive the output current through the load with the voltage limited only by the line power or saturation level of the current transformer; therefore, the secondary of a current transformer must never see an open circuit.

D

Differential motor protection

Means of detecting current leakage in a motor from winding-to-winding or from winding-to-ground. Differential motor protection requires a six lead motor. Three current transformers, one for each motor phase, monitor the current in and out of each of the motor windings. If, due to leakage or some fault within the motor, the current in and the current out are not identical in each winding, a current will be induced in the secondary of one or more of the current transformers. This induced current will energize a differential relay which will open a contactor and deenergize the motor.

Differential protection is available as part of the Enhanced

Electrical Protection Package’s supplemental motor protection option. Differential protection is not applicable to Trane’s standard, low-voltage wye-delta starters.

Differential relay

Current sensitive relay that has three coils, each connected to one of the current transformers used for differential protection. Energizing any one of the three coils will operate the relay. A differential relay is furnished with the differential protection option.

Disconnect

A device for manually isolating an electrical circuit.

Distribution fault

Transient power losses longer than 2 or 3 cycles will be detected and cause the chiller to shut down, typically within 6 cycles. The chiller can also shut down due to excessive or rapid voltage sags. Shutting down the chiller prevents the motor having power reapplied with different phasing. Utility power outages are not considered distribution faults—Trane refers to this type of fault as a momentary power loss (MPL).

E

Enclosure

The sheet metal structure and access door that surrounds the starter. The standard enclosure is NEMA Type 1, which means general purpose indoor with a gasketed access door. Other enclosure classifications to meet requirements of different environments are available as special options. See “NEMA 1,” p. 78 .

F

Full-load amps (FLA)

See “Amps, motor full-load amps (FLA)”, p. 73 .

Fuse

A device that protects a circuit by fusing (melting) open its current-responsive element due to an overcurrent or short-circuit current. A fuse protects electrical components from further damage if any one component within that system experiences a short circuit.

Fuse - dual element

A dual element fuse is a single cartridge fuse having two different current-responsive elements in series. A dual element fuse is required to carry 500 percent of its current rating for a minimum of 10 seconds. One of the current-responsive elements will have inverse time characteristics while the other element will handle larger currents without intentional time delay. Since most

CenTraVacs draw inrush currents in excess of this rated minimum ampacity during acceleration, all low-voltage

CenTraVacs with fuse protection must use dual element fuses.

Fuse rating

NEC code allows a maximum fuse rating that is

175 percent of the RLA. To prevent blowing fuses during motor acceleration this maximum value is allowed to increase up to 225 percent of the RLA. CenTraVac dual element fuses are sized at 150–195 percent of the chiller

RLA.

G

Ground fault

A leakage of line current to ground. Ground faults are typically caused by the breakdown or cracking of wire insulation.

CTV-PRB004-EN 75


Glossary

Ground fault protection—low voltage

Low voltage ground fault protection consists of a ground fault sensor, a ground fault relay, and a disconnect device

(circuit breaker or non-fused disconnect switch) equipped with a shunt trip device.

The ground fault sensor is a specially rated current transformer and must be applied only with a ground fault relay. Ground fault sensors cannot be used with any other equipment.

The ground fault relay is designed to work with a ground fault sensor. The current level required to activate the ground fault relay is adjustable. The response speed (time delay) is also adjustable to avoid nuisance trips. All ground fault relays require a manual reset. The time-current tripping curve of a ground fault relay is nearly instantaneous when the current setting and time delay have been exceeded. The contacts of the ground fault relay energize a shunt trip device to open the circuit and isolate the ground.

The shunt trip device is a circuit breaker with a shunt trip coil. Such a circuit breaker can either be opened manually, opened by its current sensing element (short circuit), or opened by energizing its shunt trip coil. A circuit breaker is used to open the circuit because it is capable of successfully interrupting fault current; the current to ground may be catastrophic.

The minimum setting of the ground fault protection system should be 20 percent of the disconnect rating with a 10-cycle time delay.

Ground fault protection—medium voltage

Medium voltage ground fault protection consists of a ground fault sensor and ground fault relay. The ground fault relay interrupts control power to the main contactors causing them to open. All medium-voltage starters are equipped with current-limiting fuses. In the event of a catastrophic ground, the current-limiting fuses would react much faster than the ground fault protection relay; therefore, the fuses would perform the act of interrupting the circuit and isolating the ground.

The minimum setting of the ground fault protection system should be 20 percent of the disconnect rating with a 10-cycle time delay.

Grounding

Electrical refrigeration components such as motors and control panels must be grounded for the protection of maintenance and service personnel.

Equipment ground connection bolts are provided in the control panel, the motor junction box, and in the starter of all CenTraVacs. On those CenTraVacs where the control panel is isolated, grounding straps are installed to ground the control panel to the chiller frame. Thus, all pieces of a

CenTraVac are provided with an individual equipment ground.

It is the responsibility of the installing contractor to ground the CenTraVac equipment to an earth ground per NEC and local codes.

“Gutless” circuit breaker

See “Non-fused disconnect”, p. 78 .

I

Inrush current

The current drawn by a motor during acceleration. Inrush current for various types of starters (in percent of LRA) is given in Figure 6, p. 18 (low voltage) and Figure 22, p. 31

(medium voltage).

Interlock, electrical

Auxiliary contacts on a contactor, typically used in control voltage circuits, to monitor the position of the contactor.

These auxiliary contacts may be normally open, normally closed, or convertible.

Interlock, mechanical

Bars, levers, or catches that physically prevent operation of a device under certain circumstances. (i.e. a CenTraVac starter door may not be opened if a circuit breaker is closed)

Interrupting capacity

The rated maximum current that a device can successfully interrupt without damage to itself. This applies to a circuit breaker or a fuse only. It is not proper to refer to a starter as having an interrupting capacity. Starters have an overall short-circuit current rating. See “Short-circuit current rating (SCCR)”, p. 79 .

Ionization

Insulated conductors carrying over 2000 volts are subject to ionization. Ionization results in the formation of gas pockets between the insulation layers. These gas pockets form areas of unequal stress that may lead to premature breakdown of the insulation. See “Stress cone (stress relief cone)”, p. 80 .

IQ digital meters

This is a starter mounted meter that digitally displays many parameters. It is a starter option, however most

76 CTV-PRB004-EN


Glossary functions are displayed as standard on the unit controller.

See the comparison tables ( Table 2, p. 13 and Table 3, p. 14 ).

Isolation switch

A device used to connect and disconnect a load to and from line power for servicing. Isolation switches are nonload break and cannot be opened under load. Trane

® medium-voltage starters have a mechanical interlock that prevents the isolation switch from being opened while the chiller is running. This is a standard item on Trane

® medium-voltage starters.

K

Kirk key

A locking arrangement between a remote disconnect switch and a starter that is designed to prevent closing the remote switch and powering the starter that is being serviced.

A single key is used and it is held captive in the disconnect switch. The disconnect switch must be opened and then locked open. The kirk key may then be removed and used to unlock the starter. The key remains captive in the starter until the starter door is closed and locked. The key may then be removed and used to unlock the disconnect switch. The switch may then be closed.

L

Lightning arrester

A device that protects electrical equipment from high voltage spikes by providing a high resistance path (an air gap) to ground—essentially an air gap small enough to allow a spark-over to occur for voltages much larger than the chiller’s operating voltage. The device provides protection by consistently conducting to ground when the magnitude of the voltage exceeds a predetermined value.

Although lightning arresters may be used alone, they are used usually in conjunction with surge protection capacitors.

The function of a lightning arrester is to limit the magnitude of a voltage spike. The function of a surge capacitor is to limit the rate of rise of a voltage spike. See

“Surge capacitor,” p. 80 .

Lightning arresters are a starter option.

Load-break switch (LBS)

A manual switch that has an interrupting rating and can be used to safely interrupt a live circuit. It is sometimes called an ADM switch. This term is typically used with mediumvoltage starters when customers want Trane to provide a load-break switch. The standard isolation switch that comes with medium-voltage starters is non-load break.

The load-break switch is a design special. The switch is housed within a 90" high, 36" wide, and 30" deep enclosure. A circuit breaker or non-fused disconnect on low-voltage starters can be used as a load-break switch.

Locked-rotor amps (LRA)

See “Amps, motor locked-rotor amps (LRA)”, p. 73 .

Lug

A device used to mechanically connect a conductor (wire) to a piece of electrical equipment. Lugs are furnished by the starter vendor. The number of wires per phase and range of wire sizes that the lugs will accept are listed in the starter submittals. The range of wire sizes indicates the maximum size wire that will fit into the lug hole and the minimum wire size that the screw can securely clamp in place. Optional lugs that accommodate different number of wires per phase and size are generally available for every starter. These can be purchased through a local vendor if required.

Note:Wire sizes “pulled” by contractor that are different from the lug sizes shown on the starter submittal will impact the lug sizes needed. In this case, the correct lug sizes must be obtained locally.

M

Maximum overcurrent protection (MOP)

The maximum overcurrent protection (MOP, or sometimes abbreviated as MOCP) appears on the chiller nameplate.

The electrical engineer often wants to know the MOP when selections are being made. It is used to assist in the sizing of fuses and circuit breakers. MOP is an output of the TOPSS selection program. Also see the discussion on fuse and circuit breaker sizing ( “Electrical System—

Ratings,” p. 49 and “Electrical System—Design

Guidelines,” p. 52 ). Use of improperly sized circuit breakers can result in nuisance trips during the starting of the chiller. For CenTraVac chillers the MOP is NOT the value used to size incoming wire (see MCA).

Minimum circuit ampacity (MCA)

This term appears on the chiller nameplate and is used by electrical engineers to determine the size and number of conductors bringing power to the starter. The formula for

MCA is 1.25 x (Primary RLA) + (4000/motor voltage), rounded up to the next whole number. The formula is

125 percent of the motor design RLA plus 100 percent of the amperage of other loads (control-power transformer,

CTV-PRB004-EN 77


Glossary oil pump motor, and purge etc.) MCA is an output of the

TOPSS selection program.

Table 11, p. 58 through

Table 16, p. 60 show power wire sizing based on the

MCA.

Molded case switch

See “Non-fused disconnect”, p. 78 .

Momentary power loss (MPL)

See “Distribution fault”, p. 75 .

Motor FLA

See “Amps, motor full-load amps (FLA)”, p. 73 .

Motor LRA

See “Amps, motor locked-rotor amps (LRA)”, p. 73 .

Motor size in kilowatts (kW)

The motor size is listed on the program output in kW. This is the motor’s full, rated capacity. There is an amperage draw associated with power draw at full capacity called full-load amps (FLA). FLA is the amperage the motor would draw if it is loaded to its full rated capacity i.e.

motor size kW. The FLA is not available from the TOPSS selection program, however can be obtained from

CenTraVac Field Sales Support.

Usually the selection RLA and kW are used as the nameplate RLA and kW. Occasionally, an engineer may decide to specify slightly higher RLA as the nameplate data to provide “extra” capability for the chiller. The higher kW and RLA cannot exceed the motor size (kW), the starter size (RLA), or the disconnect/circuit breaker size

(RLA).

N

NEMA 1

Enclosures are intended for indoor use primarily to provide a degree of protection against limited amounts of falling dirt.

NEMA 12

Enclosures are intended for indoor use primarily to provide a degree of protection against circulating dust, falling dirt, and dripping non-corrosive liquids.

NEMA 3R

Enclosures are intended for outdoor use primarily to provide a degree of protection against rain, sleet, and damage from external ice formation.

NEMA 4

Enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, hose-directed water, and damage from external ice formation.

NEMA 4X

Enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, hose-directed water, and damage from external ice formation.

Non-fused disconnect

A circuit breaker without a thermal or magnetic overcurrent element. It is used solely as a manual disconnect means. This is also called a “gutless” circuit breaker or molded case switch.

O

Overload protection

A scheme or device that monitors motor current and interrupts control power to the main contactor(s), disconnecting the motor from the line, if motor current exceeds preset limits of current and time. Motor current may be monitored directly or through current transformers.

Overload relay

A device that senses current flow to a motor. The relay can be set to trip at a certain value. If the motor attempts to draw current in excess of this value, the relay will trip, de-energizing the contactor coil, disconnecting the motor from the line.

P

Phase failure

An opening in one of the three main power leads caused by a blown fuse or broken conductor. This results in only one phase being delivered to the load. Thus, phase failure is the same as single phasing. Phase failure protection is standard on CenTraVac chillers with microprocessor-based chiller control panels and was available as a starter option on older CenTraVacs.

Phase imbalance

An imbalance in the current level or voltage level among the three phases. Phase imbalance can cause motor overheating.

Phase reversal

A change in the desired electrical phase relationship.

Phase reversal causes motors to rotate in the wrong direction.

78 CTV-PRB004-EN


Glossary

Phase failure/phase reversal relay

A device that monitors the phase relationship and opens a contact to stop the compressor motor in the event of phase failure, phase reversal or phase imbalance.

The advanced motor protection provided by the chiller controller performs the functions of a phase failure/phase reversal relay.

Pilot relay

A term describing the fact that all CenTraVac starters start and stop the compressor by means of a relay that responds to commands from the CenTraVac control panel.

Push-to-start push-buttons or any other forms of manual starting of the compressor are not allowed. The CenTraVac safeties in the control panel must not be bypassed.

Power factor

The ratio of real power (watts) to apparent power (voltamperes). Induction motors, such as CenTraVac compressor motors, require some energy for magnetizing that does no actual work and is not registered on a wattmeter.

Power factor correction capacitor (PFCC)

May be used to improve the power factor of a CenTraVac by furnishing some of the wattless magnetizing energy required by the motor.

Power factor correction capacitors are a starter option.

They are mounted in or on the starter and are typically wired to the load side of the compressor contactor. Since the capacitors are wired in parallel with the motor, the maximum capacitor size is determined by the motor.

The capacitors furnished as a starter option will correct the compressor motor to approximately 93.5 to

95.5 percent power factor at full load.

Power wiring

Refer to Table 11, p. 58 through Table 16, p. 60 for wire sizing for line and load wire associated with CenTraVac starters.

Primary power

The performance number called primary power is the kW usage at chillers full cooling capacity. The primary power will always be less than the motor size. See “Motor size in kilowatts (kW)”, p. 78 .

Primary RLA

See “Amps, primary rated-load amps (RLA)”, p. 74 .

R

Rated-load amps or running-load amps (RLA)

See “Amps, primary rated-load amps (RLA)”, p. 74 .

Relay

An electrically-operated device whose contacts switch electrical circuits. A relay is always used as a switching device within a control circuit.

Resistance temperature detector (RTD)

A device whose electrical resistance varies with its temperature. RTDs may be used to monitor motor winding temperature.

Every CenTraVac motor has three RTDs buried within its stator windings. These RTDs are connected to the

CenTraVac control panel. There, a device monitors the resistance (hence, the temperature) of the RTDs and will stop the compressor if the motor winding temperature exceeds a preset level. These are dedicated RTDs and cannot be used for any additional functions.

If motor winding RTDs are required for any other function, the RTDs required must be described and ordered as a design special. Then, a specially built motor will be provided.

S

Short circuit

An unintentional direct electrical connection from phaseto-phase or from phase to ground resulting in low resistance and very high current flow. Short circuits can result in destruction of conductors and components. Short circuits are caused by the breakdown of insulation, poor wiring, or a conductive piece of metal that accidentally comes in contact with multiple phases or between a phase and ground (i.e. tools and service equipment). See

“Available fault current (AFC)”, p. 74 .

Short-circuit current rating (SCCR)

When a short circuit occurs, there is a period of time that the short-circuit current passes to the shorted circuit before the protection device (circuit breaker or fuse) can open. This time can be as long as 0.020 seconds (1 cycle).

The short-circuit current rating of a starter is the maximum short-circuit current that it can pass safely. Components within the starter may be destroyed, but the starter cabinet will safely contain any sparks or flying debris. UL listed starters have a listed short-circuit current rating.

Short-circuit withstand rating (SCWR)

See “Short-circuit current rating (SCCR),” p. 79 .

CTV-PRB004-EN 79


Glossary

Shunt trip

A tripping coil added to a circuit breaker or non-fused disconnect to provide a means of tripping the circuit breaker with an external signal. See “Ground fault protection–low voltage”, p. 76 .

Silicone controlled rectifier (SCR)

A solid state signal controlled, one-way power switching device commonly used in solid-state starters and variablefrequency drives.

Single phase (single phasing)

See “Phase failure”, p. 78 .

Solid-state starter

A starter that starts and accelerates a motor at a preset acceleration rate and current limit. A solid state starter performs this function by modulating the current/voltage wave form delivered to the motor with silicon controlled rectifiers (SCRs). For more information on this starter type, refer to CTV-SLB017-EN ( Solid-State Starters for

Trane Chillers ).

Starter

A device consisting of both a contactor and an overload protection system or device whose purpose is to start and stop a motor and protect the motor from overcurrent.

Variable-frequency drives are also classified as starters.

Stress cone (stress relief cone)

Cables carrying above 2000 volts must have a metallic shield unless the cable is specifically listed or approved for non-shielded use. Shielding is necessary because of the danger of corona or ionization. The purpose of shielding a cable is to confine its dielectric field to the inside of the cable or conductor insulation. The shielding must be grounded at one end.

Stress cones are used to reduce and control longitudinal and radial electrical stresses at the cable end to values within safe working limits for the material used to makeup the termination. An oversized junction box at the motor may be required to accommodate stress cones.

Surge capacitor

A device that protects electrical equipment from high voltage spikes by absorbing the peak energy of the spike and then releasing it into the tail of the spike.

Although surge capacitors may be used alone, they are usually used in conjunction with lightning arresters. See

“Lightning arrester”, p. 77 .

Surge capacitors are a starter option.

Switchgear

A switchgear type starter is an across-the-line low-voltage starter that uses a circuit breaker to connect and disconnect the compressor motor to and from the line.

Usually a separate power source (i.e., 125 Vdc from a battery bank) is used to open and close the circuit breaker on demand.

Switchgear starters should be used with caution. Some switchgear starters contain a relay that will trip the circuit breaker if auxiliary power is lost. Others do not contain this auxiliary power monitoring relay. It may then be impossible to automatically disconnect the compressor motor from the line in case of a compressor, chiller or starter fault, if auxiliary power is lost while the compressor is running.

T

Top hat

A supplementary sheet-metal enclosure provided with unit-mounted medium-voltage starters and SMP cabinets to help accommodate the space requirements of stress cones.

Transducer

A device that converts a control signal from one form to another. For example, conversion of a 0–20 psig pneumatic control signal to a 4–20 milliampere electrical control signal.

Transition

Transition is the action taken by a starter when changing from one configuration to another, such as changing

(transitioning) from the wye/star configuration to the delta configuration.

Open transition … a term indicating that the motor is disconnected from the line, transition is performed and then the motor is reconnected to the line.

Closed transition … a term indicating that the motor remains connected to the line during transition.

All CenTraVac starters are closed transition. All SBO starters must be closed transition.

Open transition starters cause stresses in the motor windings that shorten motor life.

Inrush current is nearly constant during acceleration and then drops quickly to less than RLA when the motor reaches full speed. Starters using the Trane

® microprocessor controller monitor motor current continuously and initiate transition when the motor current drops below 85 percent of RLA.

80 CTV-PRB004-EN


Glossary

Trip unit

Device that opens the operating mechanism within the circuit breaker in the event of a prolonged overload or short-circuit current. To accomplish this, an internal electronic rating plug is provided, which tells the trip unit when to open the mechanism. Rating plugs are factory set within specific ranges to meet motor performance requirements and are field-adjustable.

U

Unit controller

The microprocessor controller mounted on the chiller. Also referred to as the control panel.

Vacuum break

Contacts that are encapsulated in an evacuated, ceramic bottle. Since the contacts operate in a vacuum, arcs are quickly extinguished because there are no ionized gases present to support conduction. The claimed advantages are no contact maintenance, long contact life and safety, since there is no exposed arcing. All medium- voltage starters used by Trane have vacuum break contactors.

Vacuum break contactors are used typically only on medium-voltage starters.

V

Voltage

The following voltages apply to CenTraVacs:

Control Voltage

Low Voltage

120 Vac

208–600 Vac

Medium Voltage 601–13,800 Vac

The electrical power industry refers to 2,000 through

69,000 volts as medium voltage.

Voltage monitoring relays, overvoltage relay

A relay and an adjustable line voltage monitor that will stop the chiller if the line voltage exceeds a preset value.

This overvoltage monitoring system is a lock-out type that requires manual reset at the starter.

The chiller controller provides under/overvoltage protection as standard.

Voltage monitoring relays, undervoltage relay

A nonadjustable relay that is powered directly by line voltage. If line voltage drops below 55 percent nominal voltage, the undervoltage relay will stop the chiller. This relay requires a manual reset at the starter.


Voltage monitoring relays, adjustable undervoltage relay

A relay and an adjustable line voltage monitor that will stop a chiller if line voltage drops below a preset value.

This undervoltage monitoring system is a lock-out system that requires manual reset at the starter.


W

Wattmeter

A device that displays instantaneous power (watts) in the form of a dial meter or a digital display. When a wattmeter is ordered for a starter, the wattmeter option includes all necessary transformers.

Watt-hour demand register

An option on a watt-hour meter that indicates the total power used per time period (i.e., 15 minutes). The value displayed is proportional to the electrical energy used in the unit's time period. The watt-hour demand value will only increase when the power demand in a new time period exceeds the power demand in any previous time period; thus, the demand register indicates the largest power demand in any time period. The demand register may be manually reset to zero to monitor a new series of time periods.

Watt-hour meter

A device that measures and registers the cumulative amount of electrical energy used in terms of watt-hours

(or kilowatt-hours). This is a standard feature on the unit control panel.

When a watt-hour meter is ordered for a starter, this option includes all necessary transformers.

Watt-hour meter pulse initiator

A device that generates pulses (contact closures) proportional to a definite energy value (watt-hours per pulse). Output contacts of pulse initiators are normally connected to pulse-operated demand recorders or used to feed energy consumption information to computers and load controllers.

When ordering pulse initiators, the type of pulses and the pulse rate the end devices will accept must be indicated.

Withstand rating

See “Short-circuit current rating (SCCR)”, p. 79 .

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For more information, visit www.Trane.com.

Trane has a policy of continuous product and product data improvement and reserves the right to change design and specifications without notice.

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CTV-PRB004-EN 19 Dec 2011

Supersedes CTV-PRB004-EN (17 Sep 2010)

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