Effect of design parameters on electromagnetic torque of PM machines with concentrated windings using nonlinear dynamic FEM

This paper focuses on influence of design parameters of permanent magnet machines with concentrated windings on cogging torque, torque ripple and mean torque. An efficient approach is presented to estimate the magnet width and slot opening width for minimizing cogging torque and/or maximizing mean torque. Two-dimension nonlinear finite element analysis including rotor motion is used for the calculation. The torque is calculated using different methods: Maxwell's stress tensor and Virtual work method. Comparison of results between linear and nonlinear magnetic circuit show that the torque is sensitive with magnetic saturation. The maximum torque of the linear case is about 15% higher than for the magnetic saturation case. Linkage flux, internal voltage and mean electromagnetic torque calculation are verified by experiments with error margin smaller than 1%, 2% and 3% respectively.