Proximity Losses in the Windings of High Speed Brushless Permanent Magnet AC Motors With Single Tooth Windings and Parallel Paths

Proximity and additional eddy-current losses can be difficult to calculate and if there are parallel paths then there can sometimes be increased losses which can be unexpected. The paper addresses these winding losses in a brushless permanent magnet machine with 18 slots, 16 poles and a spoke type rare earth magnet rotor. The winding has coils that are one pitch. Different simulation scenarios are investigated to illustrate the even when the windings are in slots they can still experience increased ac copper losses when rotating at high speed. High speed machines often have few series turns because of the high rate of change of flux linkage so they can have many parallel turns or strands in hand. Simulations are carried out at 12 000 r/min then some simulations are run at 4000 r/min for completeness. The simulations are run in a 2-D finite-element analysis environment.