On the Determination of the Parameters of the Equivalent Circuit of Three-Phase Induction Motors

Abstract

I consider the problem of determining the parameters of equivalent circuits of asynchronous motors with squirrel-cage and wound rotors by using catalog information to construct their mechanical characteristics. In known sources, determination of the parameters is carried out either by the selection method with variation of the ratio of the parameters, which can vary widely, or with some of the parameters being accepted equal to zero and expressions being simplified. The equivalent circuit of the asynchronous motor contains six unknown parameters of the resistance, of which only the nominal stator current and its active and reactive components are known, and so calculation of parameters is performed using well-known formulas describing the characteristics of the motor. In this work, by giving extreme values of the ratio nominal voltage to the EMF of the magnetization chain in the regime of perfect idling, which can vary within ±2.0%, the parameters of compliance with these coefficients are determined and, thus, the area of varying of the parameters of the equivalent circuit in conditions of their linearly interpolated dependence is determined. The calculation is done using equations of the second order based on the constancy of the power of electric motor, balance, and active and reactive power. Determination of the region of conformity of parameters allows making preliminary and, then, specific calculations, followed by assessment of the results of convergence solutions. This calculation method can be used in engineering practice not only for calculating parameters by means of catalog data, but also for determining the correspondence of parameters that are not defined in these data.