TM 5-3895-374-24-1
Recommendations for use
of the motor/speed controller combination
Available torque
Continuous duty: motor derating is linked to two causes
- Although the current waveform is very close to a sine wave, motor heating is slightly
greater than that obtained by direct supply from the mains. The resulting reduction in torque
is in the order of 5 % This is lower than manufacturing tolerance limits
- For self-ventilating motors, the ventilation needed for the cooling of the motor is linked to
the motor speed This results in derating, which occurs at approximately half of the rated
speed
Transient operating periods
Overtorque possibilities are linked to the maximum peak current which the controller can
provide, and the extent to which these overloads are repeated
Overspeed operation (f > 50/60 Hz)
As the voltage can no longer change with frequency, this results in a decrease of the
induction in the motor, which causes a loss in torque The manufacturer will advise whether
the motor is capable of operating in overspeed conditions
(page 3-182)
