Omron J7 series, User Manual

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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
High-speed Operation When using the motor at high-speed (60 Hz or more), problems may arise in
dynamic balance and bearing durability.
Torque Characteristics 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.
Vibration 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 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).
Torque (%)
Frequency (Hz)
100
80
70
60
50
25% ED (or 15 min)
40% ED (or 20 min)
60% ED (or 40 min)
Continuous
0 6 20 10 3 0