A method for modelling the effect of stator slotting on the magnetic field distribution in the airgap/magnet region of a radial-field brushless permanent magnet dc motor equipped with a surface mounted magnet rotor is presented to enable the analytical prediction of the open-circuit, armature-reaction, and resultant magnetic field distribution under any specified load condition. It is shown that the conventional ''1-d'' relative permeance model, which is used extensively in the analysis of induction and synchronous machines, is inappropriate for permanent magnet motors, for which the proposed analytical method accounts for stator slot openings by the application of the conformal transformation method and a ''2-d'' relative permeance function. The results of predictions from the analysis are compared with corresponding finite element analyses.
