Torque computation by mean and difference potentials (PM motors)

A technique for torque computation is proposed and applied to finding the cogging torques in a neodymium-iron-boron permanent-magnet motor. Results agree with measured values to within a few percent, within the limits of measurement accuracy and the approximations inherent in 2D analysis. When applied to the same model, the virtual work method fails to predict torque adequately. The new computational method is shown experimentally to be robust under changes of mesh fineness. Details of the method are set out and the technique of torque measurement described briefly.