Instantaneous magnetic field distribution in brushless permanent magnet DC motors. III. Effect of stator slotting

For pt.II see ibid., vol.29, no.1, p.136-142 (1993). A method for modeling 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 allow the analytical prediction of the open-circuit, armature-reaction, and consultant magnetic field distribution under any specified load condition. It is shown that the conventional 1D 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 permanence function. The results of predictions from the analysis are compared with corresponding finite element analyses