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The development of an in situ efficiency estimation technique is a challenging task where the lowest level of intrusion and the highest possible accuracy are required. In this paper, a new algorithm is discussed for the in situ efficiency estimation of induction machines under unbalanced power supplies. Prior work in the literature has concentrated on balanced supplies. In addition, to have a nonintrusive speed measurement, a specific adaptive nonlinear algorithm is applied for the extraction of the speed-dependent current harmonics from the measured current signal. A similar algorithm is used to extract the symmetrical components from the current and voltage signals to handle the unbalanced supply conditions. Experimental results with two different machines are used to prove the effectiveness and generality of the proposed method. Measurement error analysis, as well as repeatability tests, has been done to determine the credibility of the proposed method.Index Terms-Error analysis, evolutionary algorithm, induction motor, in situ efficiency estimation, nonlinear adaptive filter, repeatability test, unbalanced supply.

The efficient operation of induction machines and methods to estimate their working efficiency have received increased attention in recent years due to the growing awareness of the demand side energy management programs. Various techniques have been proposed for efficiency estimation with different requirements. Numerous works have also been published in the literature about estimating the efficiency of a machine in-situ, under the loaded condition without disturbing its operation. However, very little has been done on estimation of the efficiency of the machines after the refurbishment process in the workshops, which in fact can affect numerous machines in the industry. In this paper, a method is proposed for this purpose which requires only the no-load test. The proposed method is validated by experimental results with seven different induction machines.

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