Normalized-Characteristic-Current-Based Methodology for Quantifying Active Winding Reconfiguration Benefits in Permanent Magnet Synchronous Machines

Abstract

Abstract

Traction electric machines in electrified mobility are constrained by limited supply voltage and critical materials. Active winding reconfiguration (AWR) changes the winding connection during operation to improve voltage utilization and field-weakening (FW) capability. However, general design rules for AWR remain limited. This work extends the characteristic-current-based normalized parameter-plane framework to AWR via topology-dependent reconfiguration factors and evaluates the resulting torque-speed-power behavior over the design space. The analytical model is compared against finite-element analysis of six baseline machines and test-bench measurements from one machine. Normalized characteristic current is the dominant design parameter, capturing the balance between magnetic and current loading, while saliency and the reconfiguration factor set the magnitude of the benefit. Figures of merit are defined to quantify reconfiguration benefit across peak performance, crossover points, torque-speed envelopes, and part-load performance. Across these figures of merit, three explicit thresholds for normalized characteristic current are analytically derived and identified. Below the lowest threshold, designs such as synchronous reluctance and ferrite-assisted machines gain up to four times higher constant power speed range and 40% higher peak power, based on the analytical model. Above it and up to the middle threshold, conventional rare-earth traction machines gain mainly in part-load efficiency instead. Above the highest threshold, narrow-FW designs gain mainly in speed-range extension. These thresholds provide generalized, geometry-independent early-stage AWR screening for traction machine concepts.