Induction Machine Parameters Determination and the Impact of Stator/Rotor Leakage Split Ratio on Its Performance

Abstract

The relationship between the stator and rotor leakage reactance of the induction machine (IM) according to IEEE Std 112 is assumed to be constant under all operating conditions. However, this is not substantially accurate during severe transients such as the direct online startup and loading conditions of a three-phase induction motor. The leakage reactance of the machine can vary widely during severe conditions. Hence, using constant parameters in the machine model will result in an inaccurate dynamic performance prediction. Moreover, considering a constant ratio between the stator and rotor leakage reactance is no longer valid for all current levels. In this article, a direct and precise method is proposed to estimate and separate the stator and rotor leakage reactance parameters under normal operating conditions and when the core is deeply saturated. The method exploits the two-dimensional time-stepping finite-element method (FEM) with a coupled circuit. The obtained current-dependent reactance functions in both leakage flux paths are included in the dq-model of the IM. Other machine parameters are determined by implementing the standard tests in FEM. To verify the effectiveness of the proposed method, the predicted results are compared to the dynamic responses obtained experimentally from a three-phase, 5-hp squirrel cage IM.