Modeling of High-Frequency Common-Mode Impedances for Hairpin Winding Machines

In modern variable-speed electrical drive systems, high efficiency and power density are achieved using wide-bandgap (WBG) inverters and hairpin windings. These choices directly affect the common-mode (CM) behavior of the drive system, notably because of the faster switching speeds and different high-frequency (HF) behavior compared to conventional windings. To implement countermeasures against parasitic effects, such as electromagnetic interference or bearing currents, already within the design process, CM impedance and currents need to be predicted for drives with this altered set of parameters as well. Several CM modeling techniques have been proposed in the literature, but their applicability to modern highly integrated drive systems (HIDSs) has not yet been evaluated. In order to contribute to closing this gap, this article analyzes the HF CM characteristics of hairpin windings. The investigation clearly demonstrates the relevance of wave propagation and interactions via the neutral point for CM behavior and, consequently, for CM modeling.