Analytical prediction of cogging torque in spoke type permanent magnet motors

An analytical method is presented for calculation of no-load magnetic field distribution in the slot-less and slotted air gap of a spoke-type permanent magnet (PM) motor. The slot-less air-gap field and the relative air-gap permeance considering the effects of the slots are derived from the conformal transformation. The analytical field solutions are used to predict the cogging torque of an 8-pole, 48-slot spoke-type PM motor. The computed cogging torque using this method is compared with the 2D finite element analysis (FEA) results.