Performance Analysis of High Power Density Propulsion Motors Under Various PWM Strategies

Abstract

Compared to conventional three-phase machines, multi-three-phase machines are more susceptible to the adverse effects of voltage pulses introduced by pulse-width modulation (PWM) techniques. This increased sensitivity leads to higher current harmonics, resulting in increased machine losses, current distortion, and mechanical vibration. This paper presents a comprehensive investigation into the high-frequency harmonic losses induced by PWM in a voltage-fed electric machine. A circuit-level simulation framework is performed to evaluate the voltage excitation and the resulting current responses of the motor-inverter system under various PWM strategies. The analysis incorporates field-oriented control (FOC) with the synchronous frame PI current controller, ensuring consistent computational effort and control fidelity across all modulation schemes. To maintain a balanced trade-off between simulation accuracy and computational efficiency, the study combines finite element analysis (FEA) for machine loss estimation with a circuit-based approach for predicting PWM-induced current ripple. An in-depth electromagnetic loss breakdown is carried out to pinpoint the dominant sources of high-frequency losses. Two well established PWM techniques, known for their distinct current distortion profiles, are evaluated across a range of switching frequencies, machine operating speeds, and modulation indices. The analysis emphasizes their impact on current waveform quality and high-frequency loss behavior in the context of aerospace propulsion systems.