Mathematical Modeling of Fast and Accurate Coupled Electromagnetic-Thermal Analysis

This article proposes a fast and accurate coupled electromagnetic-thermal analysis method for a permanent magnet synchronous motor. In conventional design methods, the electric and thermal characteristics are calculated simultaneously using a finite element analysis (FEA). However, FEA requires considerable computational time. Therefore, in order to reduce the computational time, mathematical models of the electric parameters and characteristics were proposed as an alternative. Accordingly, the models of the electric parameter, such as d- and q-axis inductance and flux linkage, were obtained using a modified lumped parameter magnetic circuit containing a reluctance of an iron core. Furthermore, the models were fitted according to the formula type to consider nonlinearity according to variations in current and temperature. The electric parameters calculated by FEA were used for curve fitting. A greater number of FEA points were required to determine the effect of current and temperature on the electric parameters. Curve fitting using an appropriate formula type was performed considering the accuracy and minimum number of analysis points. Mathematical modeling of the electric characteristics, including efficiency and losses, was performed. The models of losses were coupled as heat sources to the lumped parameter thermal network, which is well known for its low computational time. The proposed coupled analysis method was applied to a reference motor; through this analysis, the electric characteristics and temperature distribution were calculated simultaneously, considering changes in losses and temperature distribution. The experimental validation was conducted with an acceptable error of 4.4%.