Efficiency estimation of induction machines using nonintrusive no-load low voltage test

Efficiency of induction machines can be determined using international efficiency test standards such as the IEEE standard 112, IEC 60034-2-1 and JEC 37. The methods presented in these standards involve tests such as the no-load test, lock rotor test and a dynamometer test. Performing the no-load test is simple with fewer requirements in terms of equipment. The dynamometer test and the locked rotor test are however not usually simple and involve expensive equipment that may not be available in motor repair/rewound workshops. Efficiency estimation after motor repair or rewound is vital in order to assess the quality of work. This paper presents a simple nonintrusive method for efficiency estimation using only no-load test measurements. The method is based on equivalent circuit parameter identification from a no-load low voltage test and the application of the identified parameters in efficiency calculation. The equivalent circuit parameters are determined by solving a nonlinear least square minimization problem using Artificial Bee Colony (ABC) optimization algorithm. Two induction motors of sizes 7.5kW and 11kW are tested and the results are compared to the IEEE std 112-B1efficiency test method. Error of less than -0.83% and -0.95% on a load range of 50% to 100% are obtained for the 7.5kW and 11kW test motors respectively.