6-2
6-1 Notes on Using the Inverter for a Motor
H Using the Inverter for an Existing Standard Motor
When
a standard motor is operated with the Inverter
, power loss is slightly higher than when operated
with a commercial power supply.
In
addition, cooling effects also diminish in the low-speed range, resulting in an increase in the motor
temperature. Therefore, the motor torque should be reduced in the low speed range.
The following graph shows the 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
24%
ED (or 15 minutes)
24% ED (or 15 minutes)
24% ED (or 15 minutes)
Torque (%)
Continuous
Frequency (Hz)
D High-speed Operation
When using the motor at a high speed (60 Hz or more), problems may arise in dynamic balance
and
bearing 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
3G3HV Series uses a high carrier PWM 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 or use the frequency jump
function to skip any frequency resonating the machine.
• Imbalanced rotor
Take special care when the motor is operated at a higher speed (60 Hz or more).
Appendix Chapter 6
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