CHAPTER 11
Using the Inverter for a Motor
Using the Inverter for a Motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
160
159
Using the Inverter for a Motor
Chapter 11
Using the Inverter for a Motor
Using Inverter for Existing Standard Motor
When a standard motor is operated with the Inverter, a power loss is lightly higher than when operated with a commercial power supply.
In addition, cooling effects also decline the low-speed range, resulting in an increase in the motor temperature. Therefore, motor torque should be reduced in the low speed range.
The following figure shows allowable load characteristics of a standard motor.
If 100% torque is continuously required in the low-speed range, use a special motor for use with Inverters.
Allowable Load Characteristics of Standard Motor
25% ED (or 15 min)
40% ED (or 20 min)
60% ED (or 40 min)
Torque (%)
100
80
70
60
50
Continuous
High-speed Operation
Torque Characteristics
Vibration
Noise
0 3 10 20
Frequency (Hz)
6 0
When using the motor at high-speed (60 Hz or more), problems may arise in dynamic balance and bearing durability.
The motor may require more acceleration torque when the motor is operated with the Inverter than when operated with a commercial power supply. Check the load torque characteristics of the machine to be used with the motor to set a proper V/f pattern.
The J7AZ Series employs high carrier PWM control to reduce motor vibration.
When the motor is operated with the Inverter, motor vibration is almost the same as when operated with a commercial power supply.
Motor vibration may, however, become greater in the following cases.
• Resonance with the natural frequency of the mechanical system
Take special care when a machine that has been operated at a constant speed is to be operated in variable speed mode.
If resonance occurs, install vibration-proof rubber on the motor base.
• Imbalance rotor
Take special care when the motor is operated at a high speed (60 Hz or more).
Noise is almost the same as when the motor is operated with a commercial power supply. Motor noise, however, becomes louder when the motor is operated at a speed higher than the rated speed (60 Hz).
160
Using the Inverter for a Motor
Chapter 11
H Using Inverter for Special Motors
Pole-changing Motor The rated input current of pole-changing motors differs from that of standard motors. Select, therefore, an appropriate Inverter according to the maximum input current of the motor to be used.
Before changing the number of poles, always make sure that the motor has stopped.
Otherwise, the overvoltage protective or overcurrent protective mechanism will be actuated, resulting in an error.
Submersible Motor
Explosion-proof Motor
The rated input current of submersible motors is higher than that of standard motors. Therefore, always select an Inverter by checking its rated output current.
When the distance between the motor and Inverter is long, use a cable thick enough to connect the motor and Inverter to prevent motor torque reduction.
When an explosion-proof motor or increased safety-type motor is to be used, it must be subject to an explosion-proof test in conjunction with the Inverter.
This is also applicable when an existing explosionproof motor is to be operated with the Inverter.
Gearmotor
Synchronous Motor
Single-phase Motor
The speed range for continuous operation differs according to the lubrication method and motor manufacturer. In particular, the continuous operation of an oil-lubricated motor in the low speed range may result in burning. If the motor is to be operated at a speed higher than 60 Hz, consult with the manufacturer.
A synchronous motor is not suitable for Inverter control.
If a group of synchronous motors is individually turned on and off, synchronism may be lost.
Do not use the Inverter for a single-phase motor.
The motor should be replaced with a 3-phase motor.
Power Transmission Mechanism (Speed Reducers, Belts, and Chains)
If an oil-lubricated gear box or speed reducer is used in the power transmission mechanism, oil lubrication will be affected when the motor operates only in the low speed range. The power transmission mechanism will make noise and experience problems with service life and durability if the motor is operated at a speed higher than 60 Hz.
Motor Burnout Caused by Insufficient Dielectric Strength of Each Phase of Motor
Surge occurs among the phases of the motor when the output voltage is switched.
If the dielectric strength of each phase of the motor is insufficient, the motor may burn out.
The dielectric strength of each phase of the motor must be higher than the maximum surge voltage. Normally, the maximum surge voltage is approximately three times the power voltage imposed on the Inverter.
161
Using the Inverter for a Motor
Revision History
Chapter 11
A manual revision code appears as a suffix to the catalog number on the front cover of the manual.
Cat. No. I63-EN-01
Revision code
01
Date
February 2006
Revision code
The following table outlines the changes made to the manual during each revision. Page numbers refer to the previous version.
Revised content
Original production
162
OMRON YASKAWA MOTION CONTROL B.V. – Wegalaan 65 – 2132 JD Hoofddorp – The Netherlands phone: +
31 (0) 23 568 74 00 – fax: +
31 (0) 23 568 74 88 – www.omronyaskawa.com
Note: Specifications subject to change without notice.
Manual No. I63-EN-01
Manual No.
I63-EN-01
VS mini J7
Compact General Purpose Inverter
USER’S ManUal
