Error analysis of efficiency estimation methods for induction motors

When conducting a laboratory experiment, there are various sources of error associated with the testing process. These errors need to be accounted for in order to validate the qualitative and quantitative values obtained from experimentation. The three major sources of error that are known to exist are instrumentation, human and methodological errors. Methods for determining the efficiency of induction machines contain all three of these errors, each needing to be quantified to ensure an accurate and reliable efficiency value. This paper focuses on the effects of instrumentation errors in determining the overall efficiency associated with the various efficiency estimation methods. The worst case error estimation (WCEE) and real error estimation (REE) techniques are employed to quantify the instrumentation errors associated with the IEC Std 34-2-1, direct and NAGT methods. The effects of stricter instrumentation tolerances placed on the NAGT method are established and indicate how efficiency determination can be improved. Additionally, the variation of WCEE and REE values with load is investigated and explained with reference to the influence coefficient required for the WCEE and REE techniques.