Modelling frequency dependency of induction machine equivalent circuit parameters

This paper briefly discusses the variation with frequency of induction machine equivalent circuit parameters. It is important to include these variations in machine models used with variable speed drive models for performance prediction. Of particular concern is the accurate calculation of induction machine electrical harmonics, and the frequency and amplitude of the airgap torque pulsations they produce. Initial attempts to improve the calculation of electrical current harmonics using existing time domain simulators were unsuccessful. A specifically developed frequency domain program was used successfully, although the frequency domain approach does have limitations. The current aim is the development of an improved time domain model that includes frequency dependency of the key parameters. The model is being developed in the C language in a format suitable for use with MATLAB and SIMULINK by compilation to a MEX-file. This approach allows maximum flexibility in the development of the motor model, combined with the functionality of a commercial simulation package.