Analytical investigation of open-circuit eddy current loss in windings of PM machines

This paper investigates open-circuit eddy current loss in the winding of surface-mounted permanent magnet machines, based on the subdomain model accounting for tooth-tips but neglecting the eddy current redistribution effect. The influence of various design parameters, such as conductor layout, slot width, slot opening width, tooth-tip height, magnet pole-arc to pole-pitch ratio, gap between tooth-tips and conductors, and air-gap length, on the open-circuit eddy current loss in the bar-shaped windings of permanent magnet machines is investigated. It is shown that radially segmenting conductors has no effect on the open-circuit eddy current distribution and losses if the number of circumferential conductor layers is 1, but can reduce the loss when it is larger than 1. The eddy loss exhibits a large drop when the number of circumferential layers is changed from 1 to 2, but shows slow reduction above this. The analytical predictions of eddy current distribution and joule loss are validated by finite element analysis.