Factors Influencing Demagnetization in NdFeB Permanent Magnet Motors

Neodymium ndfeb materials have poor thermal stability, and their high temperature coefficient can easily cause irreversible demagnetization (also known as demagnetization) when permanent magnet motors are running.

On the one hand, the eddy current of permanent magnet motors generates heat on the surface of permanent magnets, and the heat dissipation conditions inside the motor are poor, which exceeds the working temperature of permanent magnets, causing permanent magnet demagnetization. Therefore, the temperature stability of permanent magnets is crucial to motor applications.

On the other hand, the unreasonable design of the working point of the permanent magnet motor magnetic circuit is also prone to irreversible demagnetization. When the motor encounters a large demagnetization during starting, reversing and stalling, the working point of NdFeB may drop below the inflection point of the demagnetization curve, causing irreversible demagnetization. Therefore, the working point of the permanent magnet motor magnetic circuit should be designed to be higher than the inflection point of the NdFeB material. When the motor stops running, the residual magnetic induction intensity Br of the permanent magnet material remains basically unchanged.

The design of permanent magnet motors must also understand the actual operating environment of the motor and take necessary measures in assembly to ensure that it is in a stable state without demagnetization at high temperatures.

The SH grade NdFeB magnets used in motors that meet the standard requirements cannot guarantee that the motor will not lose magnetism during operation. Only by increasing the intrinsic coercive force and Curie temperature of the NdFeB magnets can the irreversible magnetic loss of the NdFeB magnets be reduced and the temperature stability of the permanent magnets be improved, thereby extending the service life of the permanent magnet motor.