Three main causes of permanent magnet demagnetization during motor use

Frequently, motor customers will encounter the problem of permanent magnet demagnetization. What is going on? What could be caused by? Today, the magnet manufacturer MPCO MAGNETICS tells everyone about the three main causes of permanent magnet demagnetization in the actual use of the motor.

First, the demagnetization caused by the permanent magnet material itself

The servo motors that we use today are all made of NdFeB permanent magnets. The NdFeB permanent magnets have the advantages of high remanence and high intrinsic coercivity. They are the most permanent magnetic materials with magnetic properties and are in the rare earth. The content is very high, iron and boron are cheap, and there is no strategic material cobalt. However, the shortcoming of NdFeB permanent magnet material is poor thermal stability. The magnetic temperature of NdFeB permanent magnets with N38SH grade is 150°C. As long as the temperature exceeds 150°C, irreversible demagnetization will occur. The iron-boron permanent magnet contains a large amount of iron and bismuth metal materials, and the surface is easily oxidized. Generally, there is an epoxy resin coating or an electrophoresis or electroplating coating. If the coating process is unqualified, the permanent oxidation of the permanent magnet may occur during use. And cause demagnetization.

permanent magnet demagnetization during motor use

permanent magnet demagnetization during motor use

Second, the demagnetization caused by the motor design

If the motor is not fully understood in the design of the motor, so that the actual working point is below the inflection point of the demagnetization curve, then irreversible demagnetization will occur during use. In addition, the working point calculated during design is usually the average working point of the permanent magnet. However, due to local differences in the permanent magnet material, the maximum demagnetization operating point of the permanent magnet must also be calculated. Moreover, the motor should be designed with full consideration of whether the internal temperature rise of the motor is within 105K. If it exceeds this range, it will cause irreversible demagnetization.

Third, the use of improper demagnetization

The environment used by the motor is bad, especially in the case of high temperature or severe mechanical vibration, the motor magnet may be demagnetized; in addition, the motor may cause irreversible demagnetization due to excessive temperature due to long-term overload of the motor.

The above is the most common reason for the motor to cause demagnetization of the permanent magnet in actual use. If you need a motor magnets, please contact MPCO MAGNETICS.

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