Efficiency Enhancement of a WBG Device-Based Rare-Earth-Free PMaSynRM Drive Considering Both Machine and Inverter Losses Via Switching-Frequency Adjustment

Synchronous reluctance motors (SynRMs) offer a sustainable alternative to electric vehicle (EV) traction drives by eliminating reliance on rare-earth materials and mitigating associated supply chain and geopolitical concerns. However, the absence of rare-earth magnets leads to reduced efficiency and power density. To address these limitations, ferrite magnets are incorporated into the rotor to realize a rare-earth-free permanent magnet-assisted SynRM (PMaSynRM), and a wide bandgap (WBG) device-based inverter is employed to further enhance efficiency and power density. In this paper, a novel loss modeling framework is developed to accurately predict the efficiency of the WBG-based PMaSynRM drive by incorporating both inverter losses and machine losses, including fundamental and pulse-width modulation (PWM)-induced components. The proposed approach leverages a double Fourier integral (DFI)-based formulation to account for switching harmonics and applies a golden section search to determine the optimal switching frequency that maximizes overall drive efficiency across different operating points. As an example, at 1200 rpm and $4 \mathrm{~N}. \mathrm{m}$, the optimal switching frequency of 64.89 kHz improves system efficiency from 83.3% at 1 kHz to 87.8%, demonstrating a performance gain unattainable with a fixed switching frequency strategy.