Abstract
In this thesis, various aspects of induction motor performance are discussed. The importance of the speed-torque curve for an induction motor system and its various applications are emphasized. Difficulties in the presently available methods of obtaining the speed-torque curve of an induction motor will justify the need for novel methods for obtaining it. First, a study of induction motor torque and torque calculation methods is presented. Effects of slot combinations, test voltage, and connected inertia, are seen to be crucial factors in the torque calculation process. Then, a study of saliency induced harmonics and their generation in a three phase induction motor follows. Presently, well established theory will be touched upon in order to aid in the physical explanation of the phenomenon. Tracking algorithms and approaches used for extracting such saliency harmonic signals from the motor current spectrum are then discussed. This section will conclude by recommending the short time fourier transform (STFT) as the most suitable method for the tracking of such nonstationary harmonic components in the current spectrum. After having thoroughly discussed induction motor torque, and saliency harmonic tracking techniques, a novel digital technique for obtaining the speed-torque curve of an induction motor is proposed. An online method of rotor inertia estimation will be used along with the motor's mechanical model and saliency harmonic tracking to obtain the complete speed curve. The air gap torque method will then be used to obtain the complete speed-torque curve in a novel sensorless way. A brief discussion and recommendations for future research then follows. Some of the myriad of applications of the speed-torque curve will then indicate the importance of it as a crucial performance determining factor.
Ahmed, Shehab (2000). Sensorless performance evaluation of induction motors. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2000 -THESIS -A381.