Separation of torque components using Frozen Permeability and Maxwell Stress Tensor

Local force distribution in motors has been widely studied to analyze the origins of torque ripple and vibration. In most cases, there are multiple force waves which need to be identified and analyzed individually. While separation of these forces and the corresponding fields is simpler if the core is below saturation limits, special techniques are required if significant portion of the core is in saturation. In this paper, Frozen Permeability and Maxwell Stress Tensor are used to separate components of air-gap forces in an Interior Permanent Magnet Synchronous Motor. The combined use of Frozen Permeability and Maxwell Stress Tensor is existing in literature. However, the approach proposed in this work allows to view reaction torque as sum of two components that have dissimilar ripple content. Nature of torque-ripple due to these two components is studied by varying the slot-design.