Finite-Element Supported Transmission-Line Models for Calculating High-Frequency Effects in Machine Windings

Wave-propagation effects in machine windings are commonly simulated on the basis of a transmission-line model (TLM) where the parameters are extracted from cross-sectional electroquasistatic and magnetoquasistatic finite-element (FE) models of a stator slot. In this paper, three improvements are proposed. First, an additional radially-axially oriented FE model deals with the complicated return path of the common-mode current through the laminated core and leads to an additional impedance to be inserted into the TLM. Secondly, an additional TLM section is constructed using parameters extracted from an axisymmetric FE model of the winding overhang. Thereby, the impedance mismatches caused by the end-winding overhangs along the wave propagation direction are incorporated in the model. Thirdly, the capacitive and inductive inter-wire couplings are taken into account. The simulation results indicate the need of all three additions.