Considerations for Nonintrusive Efficiency Estimation of Inverter-Fed Induction Motors

There has been a considerable trend in the use of inverter supplies for induction motors over sinusoidal supplies due to the requirement of efficient control of these machines in many automated systems. However, the use of inverters introduces additional losses in the motor as a result of voltage and current harmonics which impact negatively on the motor efficiency. This paper provides some considerations for nonintrusive efficiency estimation of inverter-fed induction motors, focusing on the quantification of additional losses for different harmonic equivalent circuits and the effect of voltage and current harmonics on the performance of these motors. Based on the analysis of the existing efficiency estimation methods, recommended techniques are proposed for state-of-the-art methods. An application of such techniques is presented. The future trend of the efficiency estimation of inverter-fed induction motors is highlighted. The rotor speed estimation techniques are reviewed.