C.3 How To Choose A Suitable Motor - Delta Electronics VFD-VE User Manual

C.3 How to Choose a Suitable Motor

Standard motor
When using the AC Motor Drive to operate a standard 3-phase induction motor, take the
following precautions:
1. The energy loss is greater than for an inverter duty motor.
2. Avoid running motor at low speed for a long time. Under this condition, the motor
temperature may rise above the motor rating due to limited airflow produced by the
motor's fan. Consider external forced motor cooling.
3. When the standard motor operates at low speed for long time, the output load must be
decreased.
4. The load tolerance of a standard motor is as follows:
5. If 100% continuous torque is required at low speed, it may be necessary to use a special
inverter duty motor.
6. Motor dynamic balance and rotor endurance should be considered once the operating
speed exceeds the rated speed (60Hz) of a standard motor.
7. Motor torque characteristics vary when an AC Motor Drive instead of commercial power
supply drives the motor. Check the load torque characteristics of the machine to be
connected.
8. Because of the high carrier frequency PWM control of the VFD series, pay attention to the
following motor vibration problems:
Revision Dec. 2008, 04VE, SW V2.05
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Appendix C How to Select the Right AC Motor Drive|
Load duty-cycle
25%
40%
60%
100
82
70
60
50
0
3 6 20
Frequency (Hz)
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continuous
60
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C-5