Estimation of temperature dependent equivalent circuit parameters for traction-based electric machines

The influence of temperature conditions on electric machine models is not well understood. This paper investigates modelling the temperature dependence of equivalent circuit parameters. Experiments have been performed on an induction machine to characterise its impedance response (up to 10 MHz) over the temperature range (22.4-210) oC. Using these measurements non-linear parameter estimation is performed using the Nelder-Mead method to derive temperature-dependent models, with an average absolute magnitude error of 270 Ω. The accuracy has been evaluated over the frequency range for the different temperatures and highlights where improvements are needed. This work has important applications in electric machine design and condition monitoring. Also it provides a valuable precursor towards developing age-dependent models for traction based applications.