Two-dimensional magnetic field analysis of internal-rotor permanent-magnetmotors

An improved analytical method is proposed for predicting magnetic field dis tribution in the air-gap and permanent-magnet regions of radial field topol ogy of a brushless internal-rotor permanent-magnet motor. It is a two-dimen sional model based on a conformal transformation approach a here difference s in the current density have been compensated for, The method involves a n umber of integrals of the vector potential, instead of the scalar potential found in the literature. The method is convenient for magnetic fields havi ng complicated boundaries. The motor model is formulated in polar coordinat es and accounts for the large effective air gap, resulting from the low mag netic permeability. Results of the motor analysis are compared with predict ions from corresponding finite element analysis and other analytical techni ques. They indicate the advantage of the developed approach over other rece nt analytical techniques.