About Brushless Outrunner Motor Magnet Ring

About Brushless Outrunner Motor Magnet Ring

In modern motor applications, brushless outrunner motors are widely used in fans, drones, electric skateboards, fitness equipment and other fields due to their compact structure, smooth operation and low noise. In the “power heart” of such motors, the magnetic ring, as a key magnetic component, plays a crucial role.

Brushless external rotor motor is a special structure motor with rotor placed outside and stator placed inside. Unlike the traditional internal rotor motor, the rotor of the external rotor motor is part of the motor shell itself, and the drive is realized by rotating the whole shell. The magnetic ring is the core component that is affixed or embedded in the inner wall of the rotor housing and is used to provide permanent magnet excitation. The magnetic field of the ring interacts electromagnetically with the stator windings to drive the motor, which is the basis for torque generation.

The illustration shows a typical bonded NdFeB ring for an outrunner motor.

There are four main types of magnetic ring materials for brushless outrunner motors, which have been adapted to different application requirements. Bonded and injection molded NdFeB rings: Molded by injection molding or bonded molding process, they can be molded as a whole to form a ring, and can even achieve multi-pole magnetization at one time, with high magnetic properties, which are widely used in low and medium-speed equipments, such as fans, smart home appliances, etc. The magnetic properties are slightly lower than those of sintered NdFeB rings, which can be used in low and medium speed equipments. The magnetic properties are slightly lower than those of sintered magnets, but they have obvious advantages in light weight and miniaturization. Sintered and injection molded ferrite rings: Although the magnetic properties are lower, they have the advantages of corrosion resistance and good stability, and are commonly used in low-end fans or industrial fans. In addition, there is also the use of magnetic tile splicing ring, the assembly requirements are high.

Magnetic ring polarity and magnetization mode:

The magnetic poles of the ring are usually arranged in a radial direction, i.e. the N-pole and S-pole are arranged alternately along the circumference. According to the motor design requirements, the magnetic ring can be 4-pole, 6-pole, 8-pole, 10-pole, 12-pole, 14-pole, or even more poles. The more poles, the smoother the motor runs, but the speed is relatively lower. If you need to customize all kinds of multi-pole NdFeB or Ferrite rings, please feel free to contact us, and we can also provide close to the size of the samples for testing.