3D magnetic field analysis and torque calculation of a PM spherical motor

Abstract

The model of magnetic field inside the permanent magnet spherical stepper motor is developed using integral equation method (IEM) and discrete expressions are also derived. The results by IEM and FEM show the effectiveness and advantages of IEM for the magnetic field computation on PM spherical stepper motor. Based on the results of the magnetic field distribution, a torque computation model is developed by using a modified Maxwell stress tensor method. The torque formulation in the case of one phase electrified is given and the torque-angle characteristics arc derived. Comparisons with the results computed by virtual work method demonstrate the effectiveness of Maxwell stress tensor method in the torque computation and analysis of the PM spherical stepper motor