The biggest difference between a permanent magnet generator and an excited generator is that its excitation magnetic field is generated by a permanent magnet. Permanent magnet is both a magnetic source and a component of a magnetic circuit in a motor. The magnetic properties of permanent magnets are not only related to the manufacturing process of the production plant, but also to the shape and size of the permanent magnets, the capacity of the magnetizer and the method of magnetization. Moreover, the magnetic flux and magnetomotive force that the permanent magnet can provide in the motor also vary with the material properties, size, and motor operating state of the rest of the magnetic circuit. In addition, the magnetic circuit structure of permanent magnet generators is various, the leakage magnetic circuit is very complicated and the leakage magnetic flux accounts for a large proportion, the ferromagnetic material part is relatively easy to saturate, and the magnetic permeability is nonlinear.