Frequency conversion and pole-changing speed regulation are two completely different speed regulation methods for motor products. Pole-changing speed regulation can only achieve multiple speed gears of the same motor, and the corresponding gears correspond to constant speed; The frequency conversion speed control can achieve a certain number of pole motor speed smooth transition or soft start, can make the motor under any speed stable operation.  

Permanent magnet synchronous motor also uses frequency conversion technology to achieve soft speed regulation of the motor, which can automatically adjust the motor speed according to the actual demand of the load to achieve the purpose of energy saving. 

Permanent magnet synchronous motor and asynchronous variable frequency motor have a common, that is, inverter power supply. Due to frequency converter power supply, permanent magnet synchronous motor can achieve soft start and frequency conversion operation function, but the frequency converter software control mode is different, some frequency converter manufacturers also launched a better performance of permanent magnet motor inverter. 

Permanent magnet synchronous motor is divided into the operated according to the startup mode of the permanent magnet synchronous motor with frequency control of motor speed permanent magnet synchronous motor, since the launch general adopts high performance rare-earth permanent magnet materials, permanent magnet synchronous motor with squirrel cage asynchronous start in the rotor structure, can be directly power frequency power supply using run, fixed rotational speed, also could be used for speed control inverter power supply and working conditions. The rotor of VVVF permanent magnet synchronous motor has no winding or starting mouse, so it cannot start automatically and must be driven by frequency converter. Theoretically, the rotor has no heat and no loss, and the energy saving effect is excellent. 

In view of the above content, some people may ask: how to choose permanent magnet synchronous motor? Xiaobian suggestions: Should be carried out according to the actual supporting equipment and working conditions: direct replacement of ordinary motor, should choose self-starting permanent magnet synchronous motor; For the fan and water pump load with low starting torque and energy saving mainly achieved through speed regulation, variable frequency asynchronous motor can be replaced by self-starting permanent magnet synchronous motor, and the motor performance can be improved by changing the modulation ratio or carrier ratio of variable frequency parameters, which can achieve better energy saving effect. Frequency conversion permanent magnet synchronous motor can only be used for equipment requiring wide speed regulation range (i.e. broadband working requirements) and high power density. 

The application of self-starting permanent magnet synchronous motor is earlier. In the age when frequency conversion technology is not very mature, self-starting permanent magnet synchronous motor is used in low-power industrial equipment to directly supply power from power frequency grid, which achieves obvious energy-saving effect compared with general asynchronous motor. 

From the overall demand analysis of energy saving and speed regulation, variable frequency speed regulation permanent magnet synchronous motor will become a new favorite motor of the era. With the increasing popularity of frequency conversion technology, frequency conversion speed regulating permanent magnet synchronous motor will gradually replace the use of very common induction motor into all walks of life.