Extraction of High-Frequency Phase-to-Phase Coupling in AC Machine Using Mixed-Mode Network Parameters

This paper proposes a method that extracts the phase-to-phase coupling of the three-phase stator winding of an ac motor for high-frequency characterization. Under the assumption of a symmetric structure, the multiport network parameters are obtained by the conversion of two-port mixed-mode network parameters. The proposed method simplifies the calculation to extract the impedance parameters of the three-phase winding structure without the full six-port measurement. Using the extracted parameters, we can construct a T-equivalent circuit and the corresponding transmission line model of a phase line, where the phase-to-phase coupling is distinguished from the self-coupling terms. Through the constructed equivalent circuit, the effect of the phase-to-phase coupling is clearly observed by comparing the high-frequency transmission line parameters. To verify the proposed method, the calculated input impedance is compared with the measured data.