Exact analytical method for surface-mounted permanent-magnet brushless motors

The exact analytical method is applied to compute air-gap main magnetic field distribution, cogging torque and electromotive force (EMF) in surface-mounted permanent-magnet (PM) motors. The solution regions are divided into air-gap domain, permanent magnet domain and slot domains. The Laplace's or Poisson's equations of the sub-domains are solved by the exact analytical method and the solutions are obtained using boundary and interface conditions. The actual depth of slot and distance between slots are taken into account in the computation. Air-gap magnetic field distributions, cogging torque and EMF waveform computed with the proposed analytical method are respectively compared with those issued from two-dimensional finite-element analysis and experimental waveforms, the comparison results are consistent and show the correctness and effectiveness of the proposed analytical method.