PWM-Induced Losses in Electrical Machines: An Impedance-Based Estimation Method

The continuous development of electrical machines and power electronic converters is increasingly demanding for higher efficiency targets, especially in those application fields where a limited amount of stored energy is available (e.g., electric mobility). Notably, in modern inverter-fed variable speed drives (VSDs) and integrated on-board battery chargers (iOBCs), the electrical machine losses induced by pulse-width modulation (PWM) can represent a relevant component of the overall system loss and are gathering increasing attention from both industry and academia. In this context, a novel approach to estimate the PWM-induced losses in electrical machines is proposed here, exploiting a straightforward impedance measurement in the frequency domain. The key features of the proposed methodology are its simple implementation and its wide applicability, being unaffected by the machine kind (i.e., induction and synchronous machines) and/or design characteristics. In essence, the machine phase impedance knowledge allows to derive a simple and accurate high-frequency machine loss model, commonly known as machine loss factor. This model can then be exploited to estimate the machine harmonic losses induced by a generic voltage excitation waveform.