At present, the magnetic material used in the motor is mainly NdFeb, which is also divided into sintered or bonded (injection molding) NdFeb. If NdFeb is used as motor magnet, the size of permanent magnet motor is relatively small, and light, the corresponding high servo system, high power and speed/weight ratio, high starting torque, more power saving. There are also options to use samarium cobalt or ferrite as motor magnets.
Most of the magnets used in general motors choose tile magnets, there are also circular or trapezoidal, used for different motors, so the shape of the motor is not the same. Such as permanent magnet motor or AC DC motor, linear motor, brushless motor and so on. People usually use motor magnet and motor magnet attraction and repulsive force to drive, under normal circumstances will use radial symmetric magnetizing tile to form a ring. Sintered NdFeb because it is anisotropic material, so it will be more difficult to make complex magnetization direction. At present, there are also sintered NdFeb magnetic radiating magnet, but there are many restrictions on the size and brand, and its magnetic properties are extremely unstable, the consistency is very poor, and the mold coil and magnetizing fixture are very expensive.
A magnetic field is generated after the coil is energized in the motor, and the energized wire coil is also called the electromagnet. The positive and negative poles of the magnet will repel and attract the same poles of the electromagnet. So you need magnets, otherwise if the current coil is not stressed, the motor will not spin. Because the magnet is the core part of the whole machinery, so in the motor, the vast majority of the large and medium motor will use NdFeb, there are also some special purpose electric machine will use samarium cobalt magnet, and some motor with low performance requirements will also use ferrite magnetic tile. Normal electric rotor motor is composed of nickel plating or epoxy resin ndFeb magnet, the average temperature resistance is about 120°C, and ferrite and samarium cobalt can achieve high temperature resistance of about 400°C, but relatively NdFeb in addition to low temperature resistance, all are better than samarium cobalt and ferrite.
