The difference between variable frequency permanent magnet motor and asynchronous start permanent magnet motor

According to different starting methods, permanent magnet synchronous motors are generally divided into two types: asynchronous start permanent magnet motors and variable frequency start permanent magnet motors. Both are processed and manufactured using high-performance earth permanent magnet materials. The one with a squirrel cage type in the rotor structure is Asynchronous start permanent magnet motor can be started directly by connecting to industrial frequency power supply. Asynchronous start can run synchronously. It can also be connected to a frequency converter in V/F control mode to run. The rotor structure of the variable frequency start permanent magnet motor has no squirrel cage and must be driven by a frequency converter. It operates in vector control mode, has a small starting current and has better energy saving effect.

Advantages and disadvantages of using both

1. When starting, the variable frequency permanent magnet motor will start very smoothly without any current impact on the power grid; when the permanent magnet motor is started asynchronously, the starting current will be very large during the instantaneous starting process, usually 6-6 times the rated current. 7 times, which has a great impact on the power grid.

2. In terms of operational reliability, variable frequency permanent magnet motors are far more reliable and stable than asynchronous start permanent magnet motors, because the frequency converter has a protection function for the motor. In case of excessive motor current or other faults, the frequency converter will have a protective effect.

3. In terms of material cost, due to the difference in the two rotor structures, the cost of an asynchronous start permanent magnet motor is higher than that of a variable frequency start permanent magnet motor. Relatively speaking, the price of a variable frequency permanent magnet motor is more favorable.

4. Good synchronization and the same speed. When choosing a permanent magnet motor, customers feel that it is more cost-effective to start the permanent magnet motor asynchronously. It does not need to be equipped with an inverter and the cost is low. In fact, this is not the case. It seems like this from the appearance, but in actual use, it is recommended that customers choose Variable frequency permanent magnet motors are better. Because from the perspective of energy saving effect, in the long-term operation of variable frequency permanent magnet motor, the current is smaller and the efficiency is higher, and the energy saving effect is better than that of asynchronous start permanent magnet motor. It can also be adjusted to actual working conditions through a frequency converter, so that the motor can perform work more accurately and avoid unnecessary power.