Chapter 3 How to Select the Right AC Motor Drive
|
C200 Series
3-5
3-3 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:
3 6 20 60
100
82
70
60
50
0
60%
40%
25%
to
rq
ue(
%
)
continuous
Frequency (Hz)
Load duty-cycle
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:
Resonant mechanical vibration: anti-vibration (damping) rubbers should be used to mount
equipment that runs at varying speed.
Motor imbalance: special care is required for operation at 50 or 60 Hz and higher frequency.
To avoid resonances, use the Skip frequencies.
9.
The motor fan will be very noisy when the motor speed exceeds 50 or 60Hz.
Special motors:
1.
Pole-changing (Dahlander) motor:
The rated current is differs from that of a standard motor. Please check before operation and
select the capacity of the AC motor drive carefully. When changing the pole number the motor
needs to be stopped first. If over current occurs during operation or regenerative voltage is too
high, please let the motor free run to stop (coast).
2.
Submersible motor:
The rated current is higher than that of a standard motor. Please check before operation and
choose the capacity of the AC motor drive carefully. With long motor cable between AC motor
drive and motor, available motor torque is reduced.
3.
Explosion-proof (Ex) motor:
Needs to be installed in a safe place and the wiring should comply with the (Ex) requirements.
Delta AC Motor Drives are not suitable for (Ex) areas with special precautions.
4.
Gear reduction motor:
The lubricating method of reduction gearbox and speed range for continuous operation will be
Call 1(800)985-6929 for Sales
deltaacdrives.com
sales@deltaacdrives.com
Call 1(800)985-6929 for Sales
deltaacdrives.com
sales@deltaacdrives.com
