The definition and application scope of permanent mag […]
The definition and application scope of permanent magnet motor and neodymium disc magnet is as follows:
1. Permanent magnet motors are divided into permanent magnet DC motors and permanent magnet AC motors.
1.1. Permanent magnet AC motors refer to multi-phase synchronous motors with permanent magnet rotors. In the past, ferrite and alnico disc magnet were mainly used. As the power requirements become higher and higher, ferrite and alnico disc magnets are due to magnetic energy. The product is too low to meet the requirements, and the neodymium disc magnet is now widely used in the field of high-power synchronous motors and generators. Of course, neodymium disc magnet, because rare earth resources are precious, the price of raw materials has increased exponentially, and its manufacturing cost and product price will continue to increase in the future, affecting its many applications in some low-end areas. The negative temperature coefficient and low Curie temperature of NdFeB permanent magnet also restrict its application in high-temperature applications.
1.2. Permanent magnet DC motors are divided into brushless motors and general DC motors with the commutator. The application occasions are judged from the shape of the magnet and the number of poles. In general DC motors, there are mostly 2 poles and 4 poles, and disc magnets are used as motor stators. Most of the miniature DC motors use ferrite disc magnets, which are mainly used in toys, home appliances, and cars. When using a disc magnet as a stator for a brushless motor, it generally exceeds 6 poles, so its central angle is much smaller than that of a disc magnet used in a general DC motor. However, when a disc magnet is used as the rotor of a brushless motor, it can have more than 4 or 6 poles. For 4 poles, the rotor is magnetized on the outside, and because it is assembled into a circle, its central angle is close to 90°. One point can be different from general DC motors.
2. Disc magnets have different requirements for performance and magnetic field waveforms depending on the application category. As a rotor category, its outer arc surface has high requirements, and the basic waveform requirements are sine waves. As a stator, it depends on the output requirements of the motor, sparks, and Different noise requirements are selected. The disc magnet used as the stator has a high inner arc surface field. Because of the shape and production characteristics of the disc magnet, its waveform is mainly saddle-shaped. This type of waveform has a large output, but spark noise and no-load current Big. To improve vibration and noise, reverse sparks, and reduce the no-load current, the shape and size of magnets, and mold design must be carefully designed. Among them, disc magnets of unequal thickness are now widely used. The principle is to make the disc magnet arc gas. The gap magnetic field waveform tends to flat-top wave.