Three-phase asynchronous motors, especially high-power motors, have a whistling noise during operation. It is probably because the output cable contains considerable high-order harmonic voltage and current, which causes the input voltage of the motor to be distorted, and the electromotive force of the stator and rotor is high-order harmonic. The wave further increases, and the effect makes the phase electromotive force severely distorted, and the maximum value rises a lot, resulting in serious fever of the motor coil and insulation aging and breakdown.
Because the high-order harmonic magnetic field generated by the high-order harmonics generates the additional torque of the variable-frequency speed-regulating motor, the motor produces obvious vibration and severe noise. This kind of obstruction will greatly shorten the machine life and insulation life of high-power motors.
At this moment, the whistling noise of the variable frequency speed control motor in operation often gives people an illusion that it is caused by the frequency modulation of the frequency converter, but it is not necessarily. You should first confirm the origin of howling, and then deal with it.
In the first step, the inverter recycles the V/F control and runs the motor to the highest speed;
The second step, then manipulate OFF2 of the inverter to free stop;
The third step is to identify that the motor speed drops along with the free stop process. If the howling or vibration still exists, it is not a problem of inverter control, but a problem of high-power inverter motors.
There is a resonance point in the machine transmission during operation. Explain that it is a machine-manufacturing problem, not an electronic control problem. If during the free stop process, the motor runs smoothly and there is no whistling, it is a problem of inverter control, which can be handled by adjusting the control parameters of the inverter.