Skewed Arc Neodymium Magnets

Skewed arc neodymium magnets, also known as twisted arc neodymium magnets, are special-shaped magnets that provide a solution for engineers to optimize motor performance through the combination of asymmetric shape and neodymium iron boron magnets.

Advantages of Skewed Arc Neodymium Magnets

| Reduce cogging torque or noise: When motors use NdFeB magnets, tilting the stator or rotor is a common means of reducing cogging torque or noise. Since tilting the stator makes mounting the coil windings more difficult, tilting the magnets on the rotor is a more common practice.

It is important to note that skewed arc magnets reduce flux and torque. Therefore, it is necessary to design the optimal tilt angle according to actual needs. Appropriate tilt angles can eliminate the cogging torque. If the tilt angle exceeds the optimal one, it will increase cogging torque.

Based on the same principle, the rotor segmentation dislocation method will also be used to achieve the effect of approximate inclined magnets. When the number of rotor segments reaches 5, the cogging torque can be completely ignored.

Supplementary Knowledge

Cogging torque, also known as positioning torque, specifically refers to the force that causes the rotor of a permanent magnet motor to always tend to stay in certain specific positions when it is stationary.

Due to the existence of cogging torque, the motor rotor always tends to stay in a fixed position, which will affect the control accuracy of the motor. Secondly, cogging torque is a periodic torque fluctuation, which will cause additional torque fluctuations, and the fluctuation will generate noise. The impact is particularly significant when the motor requires low rotational speed.

| Improve the efficiency of the motor: Generally, the magnets in cheap motors are in the shape of square magnets. Because they are simple to process, cheap, and cost-effective, many high-end motors will choose arc magnets. Arc magnets can bring the magnets closer to the stator, increasing the flux between them, and also keeping the air gap between the magnet and the stator consistent, making it more efficient and powerful than square magnets.

| Reduce eddy current losses: Segmented magnets have been widely used in the field of high-temperature motors. The purpose is to improve the segmented insulation of the magnets to reduce the eddy current losses generated by the magnets when the motor is running. Sometimes, epoxy coating is also applied to the surface of the magnet to increase the insulation of the skewed arc magnet.

Disadvantages of Skewed Arc Neodymium Magnets

| Generally, NdFeB magnet blanks are rectangular and require wire cutting to create a skewed arc shape, which will increase material loss and product cost.

| Since skewed arc neodymium magnets are asymmetrical in shape, it is more difficult to assemble the magnets into the motor.

Technical Parameters of Skewed Arc Neodymium Magnets

| Grades: Currently, electric vehicle drive motors mainly use magnet grades with high magnetic energy product and high coercivity, such as 45UH, 48UH, 50UH, 52UH, 42EH, 45EH, etc. A mature grain boundary diffusion process is essential.

UH series: resistant to 180°C
EH series: resistant to 200°C

| Coatings: Various coatings are available, such as Nickel coating, Epoxy coating, Zinc coating, etc.

| Magnetization Direction: Generally, the magnetization direction of skewed arc neodymium magnets is radial magnetization.

Applications of Skewed Arc Neodymium Magnets

| Servo Motor: The servo motor is a key execution component in the automation control system, and its performance directly affects the response speed and accuracy of the system. Skewed arc neodymium magnets provide high torque and fast response capabilities, allowing these motors to perform well in scenarios with high precision requirements such as industrial robots, CNC machine tools, and aerospace equipment.

| Brushless DC Motor: Brushless DC motor mainly relies on the magnetic interaction of an electronic commutator and neodymium iron boron magnet to achieve the rotation of the rotor. NdFeB magnets provide high energy density in this kind of motor, ensuring the motor’s operating characteristics of high efficiency, low noise, and long life. It is widely used in air conditioning compressors, home appliances, and medical equipment.

| Generator: NdFeB magnets also play a key role in some high-efficiency generators. For example, the permanent magnet synchronous generator used in wind turbines achieves efficient conversion of wind energy into electrical energy through the strong magnetic field provided by neodymium iron boron magnets. The high-temperature stability and corrosion resistance of NdFeB magnets ensure the reliable operation of the generator in harsh environments.