Permanent magnets models and losses in 2D FEM simulation of electrical machines

This paper presents different methods to model permanent magnet materials within the 2D finite element simulation of electrical machines and discuss them. The modeling deals with both the material magnetic properties and the circuit equations related to different parts of the machine. The emphasis is on modeling permanent magnets as part of the rotor electrical circuit. The methods presented are compared through the simulations of a previously designed machine. The simulations show large differences in the computed PM and other operation quantities of the machine due to the coupling between the filed and circuit equations. The choice of the rotor material is also discussed from the view point of losses. Low-loss lamination is found to be a better choice than solid-steel rotor construction used in some machines. Further, the inclusion of the Joule and permanent magnet losses in the field solution leads to more accurate estimation of the currents and torque.