The problem of motor insulation strength At present, the middle and small frequency converter, many are using PWM control mode. His carrier frequency is about thousands of to Shing khz, this makes the motor stator windings to withstand a very high voltage rise rate, which is equivalent to the motor to exert a very large impact voltage, so that the electric motor between the turn insulation withstand more severe test. In addition, by the PWM inverter generated by the rectangular chopper impact voltage superimposed on the motor operating voltage, the motor on the ground insulation poses a threat to the ground insulation in the high pressure of repeated impact will accelerate aging.
Second, harmonic electromagnetic noise and vibration of motor Ordinary induction motor using inverter power supply, the electromagnetic, mechanical, ventilation and other factors caused by vibration and noise become more complex. The frequency conversion power supply contains all the time harmonics and the natural space harmonics of the electromagnetic part of the motor interfere with each other, forming a variety of electromagnetic excitation force. When the frequency of the electromagnetic wave and the natural vibration frequency of the motor body are consistent or close, the resonance phenomenon will be generated, thus increasing the noise. Because of the wide range of motor working frequency and the wide range of rotational speed, it is difficult to avoid the inherent vibration frequency of various electromagnetic wave.
Third, the electric motor to the frequent start, the braking adaptation ability
Due to the use of inverter power supply, the motor can be at very low frequency and voltage with no impact current to start the way, and can use the various braking modes provided by the inverter for rapid braking, in order to achieve frequent start-up and braking to create conditions, so the motor mechanical system and electromagnetic system under the action of cyclic alternating force, Fatigue and accelerated aging of mechanical structures and insulating structures.
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