Delta Electronics AC Motor Drive VFD-G - Manual (Page 180)

Appendix C How to Select the Right AC Motor Drive|
Revision July 2008, EG03, SW V1.06 C-5
4. If the stall prevention function is activated, the accel./decel. time is automatically extended
to a length that the AC Motor Drive can handle. If the motor needs to decelerate within a
certain time with high load inertia that can’t be handled by the AC Motor Drive in the
required time, either use an external brake resistor and/or brake unit, depending on the
model, (to shorten deceleration time only) or increase the capacity for both the motor and
the AC Motor Drive.
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:
3 6 20 60
100
82
70
60
50
0
60%
40%
25%
to
rq
u
e
(%
)
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.