Reflecting Saturation in the Equivalent Circuit of a Three-Phase Induction Motor: A Numerical and Comparative Detailing

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Author(s) Peter M. Enyong
Pages 496-503
Volume 5
Issue 9
Date September, 2015
Keywords Three-Phase Induction Motor Performance, Saturation Influence.

Abstract

The equivalent circuit parameters of a 20kW 3-phase induction motor were investigated under magnetic saturation influence. The approach adopted involved determination of the unsaturated version of the equivalent circuit parameters in the first place. Saturation effect was then introduced by application of a saturation factor which was numerically obtained. In this paper, the author presents the no-load and short-circuit test results by means of which the equivalent circuit parameters were obtained. To that effect, the short-circuit test was carried out by the reduced-voltage method. The computations leading to the determination of the required saturated equivalent circuit reactances as well as the no-load current are hereby equally detailed. The motor magnetic saturation factor, Ksat, was found out to be 1.249 and the adjusted reactances to reflect saturation included 1) the stator and rotor leakage reactances, x1, and x21, respectively, which were 1.728Ω each; 2) the magnetizing reactance, xm, which was 68.29Ω. These values amounted to 19.9% decrease from the unsaturated values, giving rise to a 3.66% increase in the motor input current and a consequent 23.5% increase in the no-load current. Hence, it was observed and concluded that magnetic saturation had a reduction effect not only on the machine reactances but also on its efficiency sequel to the rise in the no-load current.

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