11-2
H 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 tem-
perature. 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 Invert-
ers.
Allowable Load Characteristics of Standard Motor
25% ED (or 15 min)
40% ED (or 20 min)
60% ED (or 40 min)
Torque (%)
Continuous
Frequency (Hz)
D High-speed Operation
When using the motor at high-speed (60 Hz or more), problems may arise in dynamic balance and bear-
ing durability.
D 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.
D Vibration
The 3G3MV 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).
Using the Inverter for a Motor Chapter 11
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