Estimation of Deep Bar Induction Motor Equivalent Circuit Parameters from Starting and Load Conditions

Abstract

The method for experimental determination of the deep-bar induction motors equivalent circuit parameters from normal operating conditions, such as no-load, starting and operation with various loads has been proposed. In these modes, instantaneous discrete values of currents, stator voltages and slip are measured and stator input resistances are determined, which are used to identify the equivalent circuit parameters of the IM with trapezoidal rotor rods. For the latter, the influence of the skin effect is taken into account using the provided analytical expressions for the skin effect coefficients for resistance and inductive reactance. The advantages of the equivalent circuit with trapezoidal rods in comparison with the generally accepted rectangular ones are shown. The efficiency of the proposed method has been tested for a number of motors via mathematical modeling, as well as according to the experimental data for a 4AZM-5000/6000 type squirrel-cage rotor induction motor with 5000 kW rated power and 6 kV stator voltage. The values of input resistances obtained experimentally and according to the designed equivalent circuit differ by no more than 5%, which makes it possible to recommend the developed method to be used in practice.