Air-gap layers and adaptive mesh generation for torque calculations in rotating electrical machines

An error estimation technique based on the L₂ error norm is implemented in this paper for magnetostatic finite-element analysis. Convergence of both the global and local errors are used as indicators. The air gap is refined based on the rate of change in the calculated force and consists of layers. Results that highlight the accuracy of the combined methods for cogging torque calculations are displayed for machines with odd number of slots without periodicity with and without bifurcation, and for a machine with bifurcated or pitted teeth. These machines have low cogging torque values that are difficult to compute accurately. This paper outlines the adaptive mesh generation available in the BLDC motor design software ldquoSamariumrdquo.