Improved finite element computations of torque in brushless permanent magnet motors

Two new finite element (FE) methods for improved electromagnetic torque computation are proposed in the paper. The first method uses an analytical filter applied to the Maxwell stress tensor calculation. The second method is based on the virtual work principle and directly provides the separation of torque in its average and pulsating components. The FE computational methods are validated on a brushless PM motor having a rotor with surface mounted ferrite arcs. The relative merits of each method are discussed, together with computational issues, such as the influence of the meshing and the convergence of the calculation.