Magnetic Field Analysis of Multi-Flux-Barrier Interior Permanent-Magnet Motors Through Conformal Mapping

An extended analytical method for predicting the open-circuit air-gap field distribution in interior permanent magnet (IPM) machines equipped with multilayer Permanent Magnets (PMs) is proposed in this paper. This presented method is based on the conformal mapping technique. The mapping is used to calculate the relative permeances, which consider the effect of stator slots and rotor saliency on the magnetic field distribution. The open-circuit air-gap field distribution in a multi-flux-barrier IPM can be predicted through the superposition principle. The analytical solution is implemented on: an eight-pole, 50 kW IPM motor used in 2004 Toyota Prius hybrid electric vehicle and four IPMs with two, three, four, and five flux barriers per pole. To verify this extended method, the results are compared with those obtained from the finite-element analysis.