Permanent magnet synchronous motors rarely use two poles? Why is that? The professional questions will be handed to the professionals for answers. Bei Ke magic has sorted out the answers from several electrical engineers, hoping to help you.
1. The permanent magnet synchronous machine is not easy to do
The power factor is too low when the number of poles is too many, so the asynchronous machine should generally avoid the situation of too many poles. On the contrary, it is not easy to make a permanent magnet machine with a small pole number, such as 2-pole or 4-pole, so it often makes a multi pole number, such as 8-pole or more
2. For permanent magnet synchronous motor, most of them are frequency conversion power supply. Except for high speed, the pole number has a wide range of options. The disadvantages of 2p are that the winding end is too long, the yoke magnetic density is high, the volume of the yoke is wasted, the outer diameter of the rotor is small, the torque density is small, the layout of the rotor magnetic steel is not free, and the air gap magnetic density is difficult to compare the sine. In addition, the downward constant torque speed regulation has advantages of small copper consumption and large iron consumption, so it is beneficial to increase the number of poles appropriately.