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Department of Electrica1 and Computer Engineering, University of Kuwait, P.O. Box 5969, Safat 13060, Kuwait

ABSTRACT

This paper presents a mathematical model for the magnetizing reactance in terms of voltage, frequency, load torque and motor rating. This model is derived from no-load test data. Using this model the steady-state performance of three different motors excited from three different variable frequencies has been calculated and correlated with the results predicted by the conventional value of the magnetizing reactance. This study clearly demonstrates an improvement in predicting machine steady-state performance. Because the mathematical model simplifies the steady-state analysis, it should prove equally useful in minimizing the computational rime. All motors, when excited from sources represented by the minimum power relationship, show their best steady-state performance at frequencies less than rated frequency. When excited from sources represented by direct relationship, these motors will exhibit the best msteady-state performance at frequencies close to rated value.