All household appliances generate different levels of harmonic voltage and current when the motor is running, making the motor run under non-sinusoidal voltage and current. Higher harmonics will cause the increase of motor stator copper loss, rotor copper (aluminum) loss, iron loss and additional loss, the most significant is the rotor copper (aluminum) loss. Because the ordinary AC asynchronous motor rotates at a synchronous speed close to the fundamental frequency, therefore, after the high-order harmonic voltage cuts the rotor bar with a large slip, a large rotor loss will be generated. In addition, additional copper loss due to skin effect needs to be considered. These losses will cause the motor to generate extra heat, reduce efficiency, and reduce output power. However, if a variable frequency motor is used, its energy consumption can be reduced by about 20% to 30%.
The vibration and noise of ordinary asynchronous motors due to electromagnetic, mechanical, ventilation and other factors become more complicated. The various time harmonics contained in the variable frequency power supply interfere with the inherent space harmonics of the electromagnetic part of the motor to form various electromagnetic excitation forces. When the frequency of the electromagnetic force wave is the same as or close to the natural vibration frequency of the motor body, a resonance phenomenon will occur, thereby increasing the noise. Due to the wide operating frequency range of the motor and the large range of speed variation, it is difficult for the frequency of various electromagnetic force waves to avoid the natural vibration frequency of each component of the motor. But vfd compatible motor can effectively solve these problems.
Stepless speed regulation is from stop to the fastest speed, or from the fastest speed to stop, without gears, it is gradually faster or slower. In addition, the full DC variable frequency motor can divide the motor speed gear into many gears through the frequency converter to control the motor speed and actual demand, while the maximum number of gears of the AC brushed motor is only 3 gears, and the wind speed adjustment cannot achieve the effect of frequency conversion. When the motor speed is reduced, the torque is also reduced, and the calorific value is also reduced. It is suitable to use ordinary motors for frequency conversion, but the time is no longer lower than 40% synchronous speed. For other loads, when running at 60% synchronous speed and above, use ordinary motors. When running at a synchronous speed of 25% to 60%, an external forced cooling cage motor, that is, a special ccs motor VFD electric motor, is selected. When the speed is lower than 25% of the synchronous speed, the completely forced cooling motor is selected. That is, the vector special motor.