Reduction of cogging force in PM linear motors by pole-shifting

A technique is described to reduce cogging force in permanent-magnet linear motors due to the interaction between the permanent magnets (PMs) and the stator teeth. It consists of a proper shift of the PMs so that this effect is compensated for among the poles of the machine. This technique, generally adopted for surface-mounted PM motors only, is also applied to interior PM motors. The rules to arrange the magnets appropriately are illustrated and the technique is verified by finite-element analysis and some experimental tests.