Effect of AC losses on temperature rise distribution in concentrated windings of permanent magnet synchronous machines with parallel strands

This paper investigates the effect of AC losses on the steady-state temperature rise distribution in concentrated windings of permanent magnet machines with parallel strands by combined electromagnetic and thermal finite-element analyses. The copper losses are decomposed into DC loss, strand-level AC loss and bundle-level AC loss. It shows that the AC losses can significantly increase the winding temperature and influence the temperature distribution in the slot. The bundle-level loss becomes dominant at high speed but has a small influence on the location of the hot spot in the slot, while the strand-level loss could pull the hot spot to the slot opening. A 12-slot 10-pole FSCW permanent magnet machine was prototyped and measured to validate the effect of AC losses on the winding temperature rise. The obtained results could be helpful for designers to build a detailed lumped-parameter thermal model of the winding or for the manufactures where to insert a thermal sensor to capture the real hot spot in the slot.