Brushless motors (BLDC motors) are widely used in industries, home appliances, power tools and other fields due to their high efficiency and reliable performance. However, as the use time increases, the motor may experience magnet demagnetization failure, which directly affects the motor’s operating efficiency and stability. Magnet demagnetization can cause the motor’s output power to drop, torque to be insufficient, and even the motor cannot start. X-TEAM will discuss in detail the causes, manifestations and solutions of brushless motor magnet demagnetization failure.
- Causes of magnet demagnetization
1) High temperature environment
The permanent magnets (magnets) of brushless motors are prone to demagnetization at high temperatures. The demagnetization temperature of the magnet depends on its material. Common rare earth magnets (such as neodymium iron boron) will lose some of their magnetism at high temperatures, resulting in a decrease in motor performance. Excessive operating temperature, especially when the motor is overloaded for a long time or the heat dissipation is poor, may accelerate the demagnetization of the magnet.
2) Overload operation
When the motor is overloaded or overloaded for a long time, in addition to excessive current, it may also generate excessively high temperatures, further exacerbating the demagnetization process of the magnet. In particular, when the load of the brushless motor is outside the design range, it is easy to cause the magnet to overheat and cause demagnetization.
3) Motor collision or mechanical shock
The magnet itself is a brittle material, and it may cause partial magnetic loss when subjected to external shock or collision. During the operation of some equipment, the motor encounters mechanical shocks such as vibration and collision, which may damage the structure of the magnet and cause it to demagnetize.
4) Current fluctuation or driver failure
The fluctuation or instability of the current can also cause the magnet to demagnetize. The brushless motor relies on the driver to accurately control the current. If the drive system fails, it may cause the current to be too large or too small, which in turn affects the magnetism of the magnet.
- Performance of magnet demagnetization
1) Power reduction
When the motor magnet is demagnetized, the magnetic field strength is weakened and the output power of the motor will drop significantly. The motor becomes powerless, the load cannot be driven normally, and even under light load conditions, the speed may be insufficient.
2) Difficult to start
The demagnetized motor may have difficulty starting, the motor cannot reach the expected speed, or even cannot start at all.
3) Increased vibration and noise
After the magnet is demagnetized, the magnetic field between the rotor and stator of the motor is unbalanced, which may cause abnormal vibration and noise when the motor is running, affecting the smooth operation of the motor.
- Solutions to magnet demagnetization
1) Control the working temperature
To prevent magnet demagnetization, ensure that the temperature of the motor working environment is within the design range. Using an efficient heat dissipation system and avoiding long-term operation under overload can effectively reduce the risk of demagnetization.
2) Avoid overload and mechanical shock
Try to avoid long-term overload operation of the motor and ensure that the load is within the rated range of the motor. In addition, reduce external shock or vibration to the motor to avoid physical damage to the magnet.
3) Check the drive system
Regularly check the motor’s drive and control system to ensure stable current output and avoid demagnetization problems caused by current fluctuations.
4) Replace the demagnetized magnet
If the magnet has been significantly demagnetized and cannot be restored to its original magnetism, it is necessary to consider replacing the magnet. For some applications with high precision requirements, the use of higher quality permanent magnet materials (such as NdFeB) can effectively improve the motor’s anti-demagnetization ability.
The magnet demagnetization failure of brushless motors is a common problem that affects motor performance, mainly caused by factors such as high temperature, overload, impact and drive failure. Understanding the causes and manifestations of demagnetization and taking effective preventive and maintenance measures can effectively extend the service life of the motor and restore its stable working performance. Regularly checking the operating status of the motor and maintaining a good working environment are the key to ensuring long-term and efficient operation of the motor.
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