Dynamic Irreversible Demagnetization Behavior of Line-start Permanent Magnet Synchronous Motors in the Starting Process

AbstractIn the starting process of line-start permanent magnet synchronous motors, the relative lower flux density of the working point may cause irreversible demagnetization of permanent magnets. To research the dynamic irreversible demagnetization behavior, this article presents a sloped linear demagnetization model based on the time-stepping finite-element method. In this model, a new searching algorithm is used to quickly update the recoil line and the effective coercivity of each permanent magnet element so that the dynamic irreversible demagnetization effect can be considered effectively. Then the relationship between the demagnetization field and the rotor speed is studied, and the operation performances of the line-start permanent magnet synchronous motor after demagnetization in the starting process with different load conditions are compared. It is shown that the demagnetization field becomes larger with the rise of the rotor speed, and the demagnetization is more severe after a longer starting ...