Strand-level proximity losses in PM machines designed for high-speed operation

The stator windings of surface PM synchronous machines with fractional-slot concentrated windings are vulnerable to high proximity losses when operated at high speeds due to their typically high pole numbers and resulting high electrical frequencies. The limitations of an existing 1-D flux density model are demonstrated and an improved 2-D analytical model is introduced for estimating flux densities and stand-level proximity losses inside the slots. The 2-D analytical model is shown to provide good matches with finite element analysis for the predicted flux densities and proximity losses inside a rectangular slot with a variable slot opening and electrical frequency.