Reduction of Circulating Current by Bundle Inversion in Electrical Machines with Distributed Winding

This study investigates the AC loss reduction caused by circulating current in electrical machines that use multiparallel round-wire bundles. The circulating current in these strands results from the variation of strand inductance. This inductance difference is caused by the relative position of strands in the slot of the stator core. In this study, we proposed a new winding method of bundle inversion to average the inductance variation, resulting in the reduction of the circulating current. The multiparallel round-wire bundles were inserted into the stator core slot for distributed winding, in which every wire was tagged to identify the position in the slot. The finite element method (FEM) simulation model was constructed based on these tagged wire positions, and the circulating currents with and without the proposed bundle inversion were calculated using FEM. The results showed that the proposed bundle inversion reduced the circulating current, and AC loss was reduced by 98%.