Modeling of Stator Teeth-Tip Iron Losses in Fractional-Slot Concentrated Winding Surface PM Machines

This paper presents a model for estimating the iron losses in the stator teeth tips of surface permanent magnet (SPM) machines with fractional-slot concentrated windings based on simplified semi-analytical solutions for the machine flux densities. This model is being developed for use in machine design optimization software that analyzes very large numbers of candidate designs. Tooth tip design details are important because a significant fraction of the total stator iron losses is concentrated in these structures during high-speed operation. The first model in this paper focuses on closed-form solutions for no-load operation. It is shown that the simplified model can estimate the stator losses predicted by finite element (FE) analysis within 15% while consuming less than 0.1% of the calculation time required for FE analysis. Armature reaction is included by means of conformal mapping analysis that makes it possible to predict the tooth-tip losses during loaded operation within 15% of the FE results.