Measurement analysis and efficiency estimation of three-phase induction machines using instantaneous electrical quantities

Estimating the operating efficiency of an induction machine is of prime importance for modern plant management. An extensive testing program of present efficiency estimation techniques was performed at the Motor Systems Resource Facility (MSRF), during which serious shortcomings of the existing techniques were identified.; The objective of the work of this dissertation was to develop and investigate an alternative method of efficiency estimation, which imposes a substantially lower level of intrusion than the previous existing methods, without compromising typically achieved accuracies. A two-axis model of a three-phase induction machine was developed, in which components of current, power and impedance due to rotor asymmetries are investigated. The predicted current sidebands were verified in a laboratory setting and subsequently used for speed prediction of the operating load point. Operating torque was estimated via two axis analysis of the induction machine. With the knowledge of torque and operating speed, output power can be calculated. Input power is measured with the current and voltage sensor array used for output power estimation. Efficiency is obtained as the ratio of output to input power.; A proof of concept laboratory implementation of the suggested method is presented. Seven induction machines were tested on a dynamometer at four load points, verifying predicted accuracies of the implemented technique.