Investigation of the torque calculation of a DC PM motor

The determination of the reluctance torque calculation error for different rotor positions using the finite-element method is presented. For this purpose, a special model of the motor with a full rotor is used. The reluctance torque value of this model is known for all rotor positions. Each deviation of the calculated torque from this value represents the error of the calculation. The torques are calculated according to the Maxwell stress method (MSM), the virtual work method, and the magnetizing current method. A comparison of measurement and calculation results is included. It has been established that the best results are obtained by the MSM method with the smallest number of elements. When this method is used, it is necessary to choose the proper integration path and to confine the discretization refinement to it