FEA-based investigation of the iron loss of fractional slot PM machines under flux weakening operation

The prediction of iron losses is of great importance in AC machines especially in PM brushless ones. This statement is further confirmed when dealing with fractional slot PM machines (FSPMM) since a wide speed range can be achieved. The paper is devoted to an investigation of the iron loss in both stator and rotor yoke as well as in a 12 slot/10 pole FSPMM. Based on FEA, the investigation focuses on the assessment of iron loss in the flux weakening range in so far as their increase could be a critical issue. The FEA post-processing has led to the iron loss density maps considering low and high speeds. Moreover, an analysis of the variation of the iron loss with respect to speed has been carried out. It has been found that the efficiency of the machine is greatly affected in the flux weakening range which is due to the remarkable increase of the PM eddy current loss. In order to overcome this limitation, radial segmentation of the PMs is proposed and its effect on the iron loss is analyzed.