Reduction of Eddy-Current Losses in Fractional-Slot Concentrated-Winding Synchronous PM Machines

This paper presents the results of an investigation focused on the rotor eddy-current losses of a permanent magnet (PM) synchronous machine that is equipped with fractional-slot concentrated windings (FSCWs). Major spatial harmonics that induce the most significant rotor eddy-current losses are identified and evaluated. Time-stepped finite-element analysis results are presented to compare the predicted losses in the proposed FSCW-PM machine designs. It is shown that the lowest total eddy-current losses in the rotor core and magnets are achieved by introducing flux barriers into the rotor back iron along the d-axis.