Extending Winding Function Theory to Incorporate Secondary Effects in the Design of Induction Machines and Drives

High-performance electric drive applications necessitate a high fidelity model to predict the terminal characteristics of machines in the design stage to fulfill a system-level evaluation together with the converters. This article interprets winding function theory (WFT) from the field perspective and incorporates secondary effects, such as slotting and iron nonlinearity into it to accurately predict the main flux linkage in induction machines. The method is centered on resolving the magnetic scalar potential on the two sides of the air gap and computes the flux linkage via a winding function. Its performance is benchmarked against 2-D finite-element analysis (FEA) and the state-of-the-art magnetic equivalent circuit (MEC) method. Flux linkage and torque results indicate that the relative error is within 3.1% even in a highly saturated region when comparing to FEA, while MEC using the same circuit network may present a 20% error.