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Analysis and Reduction of Circulating Current Loss of Armature Wires in Permanent Magnet Synchronous Machines

In this paper, we investigate the loss reduction of permanent magnet machines, whose armature windings consist of parallel wires. First, the impact of the loss caused by the circulating currents in the parallel armature wires is estimated by finite element analysis. The calculated total electrical loss is compared with the experimental result of a prototype motor. The measured and calculated results are found to be in good agreement. In addition, it is revealed that the circulating armature current loss is larger than the usual copper loss, which is estimated only by the total armature current and the armature winding resistance. Next, the loss reduction by reducing the number of parallel wires is discussed. The optimal number of parallel wires is found by considering the tradeoff between the reduction of circulating current loss and increase in the usual copper loss.