Multiphysics analysis of a high loss induction motor.

Abstract

In Carelian Drives and Motor Centre (CDMC) different models to predict an electric machine behavior are been developed. Among them, a thermal model is needed to simulate the temperature distribution inside a motor. Since is difficult to identify the losses in machines with high efficiency, a test motor built with a high loss electrical steel is considered to build a simple and accurate model, which is the goal of this thesis. This work presents an electromagnetic and thermal analysis of an induction motor manufactured with an electrical steel which presents high iron losses to identify the eddy current and hysteresis losses more easily which are one of the main sources of heat in an electric machine. First, the electromagnetic analysis is carried out to find the losses distribution inside the machine. In order to do this, an analytical approach was used to find the Joule stator and rotor losses. The iron losses were found using an FEA software, where using the mass-loss curve provided by the manufacturer, the coefficients needed for the calculation were obtained. These values are going to be use as input data for the thermal analysis. Then, the thermal analysis was done, first with the lumped parameter method (LPM). With this technique, a thermal circuit was built to obtain the temperature distribution inside the induction machine. Using the conductance matrix method, as in electric circuits, the node’s voltages were obtained, which in the context of thermal networks, are the temperature of each part of the motor. Also, a finite element method analysis (FEA) was carried out to solve the heat transfer problem inside the motor and obtain the temperature distribution. After the simulation were done, the LPM results and the FEA results were compare to experimental data to validate the models. The results showed a better accuracy from the FEA model, but the LPM model only reach around a 5% error with respect to the validation data.