Variable frequency and variable pole speed regulation are two completely . Variable pole speed regulation can only achieve multiple speed gears for the same motor, and the corresponding gears correspond to constant speeds; while variable frequency speed regulation can achieve smooth speed transition or soft start of a motor with a certain number of poles, allowing the motor to run stably at any speed.

Permanent magnet synchronous motors also use frequency conversion technology to achieve soft speed regulation of the motor, and can automatically adjust the motor speed according to the actual needs of the load to achieve energy saving.

Permanent magnet synchronous motors and asynchronous variable frequency motors have one thing in common, that is, they are powered by a frequency converter. Because of the frequency converter power supply, permanent magnet synchronous motors can achieve soft start and variable frequency operation functions, but the frequency converter software control method is different. Some frequency converter manufacturers have also launched special frequency converters for permanent magnet motors with better performance.

Permanent magnet synchronous motors are divided into self-starting permanent magnet synchronous motors and variable frequency speed permanent magnet synchronous motors according to the starting mode. Self-starting permanent magnet synchronous motors generally use high-performance rare earth permanent magnet materials and have asynchronous starting cages in the rotor structure. They can be directly powered by industrial frequency and run at a fixed speed, or they can be powered by a frequency converter and used for speed regulation. The variable frequency speed permanent magnet synchronous motor has no winding or starting cage in the rotor, cannot start automatically, and must be driven by a dedicated frequency converter. In theory, the rotor does not heat up or lose, and the energy saving effect is extremely good.

In view of the above, some people may ask: How to choose a permanent magnet synchronous motor? Ms. Shen suggested that it should be selected according to the actual supporting equipment and working conditions: for direct replacement of ordinary motors, self-starting permanent magnet synchronous motors should be selected; for fan and water pump loads that do not require high starting torque and mainly achieve energy saving through speed regulation, self-starting permanent magnet synchronous motors can be used to replace variable frequency asynchronous motors. Similarly, by changing the modulation ratio or carrier ratio of the frequency conversion parameters to improve the motor performance, better energy saving effects can be achieved; for equipment that requires a wide speed regulation range (i.e. wide-band working requirements) and high power density, only variable frequency speed regulation permanent magnet synchronous motors can be used.

Self-starting permanent magnet synchronous motors were used very early. When frequency conversion technology was not yet fully mature, self-starting permanent magnet synchronous motors were used on small-power industrial equipment. They were directly powered by the industrial frequency power grid, achieving significant energy saving compared to general asynchronous motors.

From the overall demand analysis of energy saving and speed regulation, variable frequency speed regulation permanent magnet synchronous motor will become the new favorite motor of the era. As frequency conversion technology becomes more and more popular, variable frequency speed regulation permanent magnet synchronous motor will gradually replace the most widely used asynchronous motor and enter various industries.