A general investigation on the differential leakage factor for symmetrical and asymmetrical multiphase winding design

This work provides an investigation based on a fast estimation of the degree of unbalance (D.U.%) and the differential leakage factor (σ0) of multiphase electrical machine windings. This analysis is carried out by exploring almost 5000 combinations in terms of number of slots, pole pairs, phases and layers. The variability of the leakage factor is examined for each condition, defining an optimal region for its minimization. As a result, an extended mapping is carried out for both the degree of unbalance and the leakage factor, providing a useful tool during the early design stage of winding configurations for multiphase electric machines, even with slight asymmetries. The results obtained from this investigation are validated through finite element analysis and demonstrate that the differential leakage factor can be significantly reduced by adopting winding configurations with slight asymmetries, which also represent a valuable alternative in the electrical machine design.