Low Voltage—Solid-State. Trane Drives, CVHG, Starters, CVHF, Electrical Components, CVHE, CDHG, CDHF

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Low-Voltage Starter Types

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

Starting sequence

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

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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.

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Low-Voltage Starter Types

Features

• Unit- and floor-mounted models are available

• Control-power transformer

• 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"

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Low-Voltage Starter Types

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

5. 4 kVA control-power transformer

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3 4 5

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% to 95%

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

• Voltage utilization range ±10%

CTV-PRB004-EN