A Simplified Equivalent Circuit Method for Induction Machine Nonintrusive Field Efficiency Estimation

Energy efficiency estimation for in-service induction motors has become a crucial area of research due to the increasing need for energy savings and demand-side management. As a result, several in-service efficiency estimation methods for induction motors have been proposed. This article presents a nonintrusive method for estimating the efficiency of induction motors operating on-site using limited terminal measurements and motor nameplate data. The method uses a modified inverse Γ-model equivalent circuit with series core loss arrangement to mitigate the inherent problems of higher computational burden and parameter redundancy in the conventional T-model. Furthermore, a new method is presented for estimating the friction and windage loss using the airgap torque and motor nameplate data. The proposed nonintrusive field efficiency estimation technique was validated experimentally on standard and premium efficiency induction motors for both balanced and unbalanced voltage supply. The results demonstrate the accuracy of the proposed method and confirm its advantage over the conventional method for in-service efficiency determination.