Modeling for open circuit magnetic field prediction in slotted surface-mounted permanent-magnet machine

A simplified analytical method is presented to study the open-circuit magnetic field in surface-mounted permanent-magnet(PM) motors, considering the effect of stator slotting. First, flux density on the stator surface with slots and teeth is described by employing the magnetic equivalent circuit(MEC) method. With the flux density and other boundary conditions, magnetic field distribution within a pole region is obtained by solving Laplace's and Poisson's equations. Further, solutions are expanded to the whole motor region through residual magnetization vector modulation function. This analytical model combines the advantages of MEC method and analytical method, and provides a useful and quick tool for predicting the open-circuit magnetic field in radial magnetization condition. It is validated by the finite element(FE) simulation for both internal and external rotor topologies, and can be further used to investigate the performances of back EMF and torque.