The motor is driven by a powerful permanent magnet. The most widely used is sintered NdFeB magnet. At present, radial (multipole sintered neodymium iron boron) magnets have replaced traditional assembly blocks or arc magnets and have become the mainstream magnets for micro motors.
The radial ring sintered NdFeB magnets are relatively mature products, which can significantly improve the output characteristics of the motor and reduce the loss of the motor. They are manufactured by a new technology-hot press. The hot-pressing production process includes milling, hot pressing and thermal deformation. Compared with ordinary sintered materials, it does not require magnetic field-oriented forming and sintering. This is because its radial orientation is formed during the thermal deformation of the material, and its internal structure is a nanocrystalline structure. They can be magnetized into multi-pole, deflection multi-pole and radial unipolar (a unipolar magnet means that the magnet has only a pair of north and south poles).
(1) The sintered NdFeB magnets reduce a lot of assembly costs.
(2) It has high dimensional accuracy.
(3) It can reduce the air gap of the motor to increase the power density.
(4) It can reduce the number of poles and deflection angle of cogging torque.
(5) The magnetic flux waveform can be controlled by a rectangle to be sinusoidal.
(6) It has excellent temperature stability, corrosion resistance and time stability.
(7) It can reduce the noise of the motor.
(1) It has a high flux density.
(2) It can realize the efficient utilization of rare earth permanent magnets.
(3) The non-magnetic material rotor shaft can reduce the weight of the motor without reducing the performance of the magnet.
(4) It makes the motor design smaller and lighter.
For example, power tools, synchronous motors, stepping motors, brushless DC motors, peripheral motors, spindle motors, steering control motors and so on.