Ordinary motors are not suitable for use as variable frequency speed control motors controlled by frequency converters because there are significant differences in design between ordinary motors and true variable frequency motors. Variable frequency motors mainly consider how to reduce the losses caused by various high-order harmonics and improve the insulation of the coils, while ordinary motors do not have high requirements in these aspects. If you want to solve the problem, it is easier to buy a true variable frequency motor.
Two questions:
1) Incorrect motor selection. If you want to use a frequency converter to drive a motor, you should use a variable frequency motor. There is a big difference in insulation performance between ordinary motors and variable frequency motors.
2) Regarding the issue that the frequency converter still does not provide protection after the motor burns out, the rationality of the frequency converter selection needs to be carefully considered.
1) Is there a filter device added after the frequency converter?
2) Is the inverter and motor a one-to-two configuration? Is the circuit design correct in this case? We have also encountered a situation where one inverter drives two motors, but the control circuit was poorly designed and always burned out the windings. Under the same operating conditions, one motor with one inverter works fine. You can check the control circuit.
3) For inverter operation, choose a variable frequency motor or reinforced insulation.
The voltage output by the frequency converter is a pulse voltage. When it is transmitted through the cable, if the cable impedance does not match the load impedance, reflection will occur at the load end. As a result, the incident wave and the reflected wave superimpose, forming a higher voltage. Excessively high voltage spikes are applied to the motor stator windings, causing voltage surges in the windings. Frequent overvoltage surges can lead to premature motor failure. The higher the frequency converter's carrier frequency, the more voltage spikes are generated per second.
