Low Speed Performance Operation of Induction Motors Drives Using Low-Resolution Speed Sensor

In this paper, indirect field oriented control (IFOC) of induction motor at very low speed range (1-5 rpm) using a low-count encoder is presented. To test the lowest possible pulse encoder that gives both satisfactory performance for IFOC algorithm and precise enough speed information, a low-count encoder implementation algorithm is developed. This algorithm converts high-resolution encoder data to various number of pulse low-count encoders. Using this algorithm, different pulse encoders are tested and the lowest possible pulse encoder is selected for IFOC implementation due to the cost limitation. Furthermore, solutions to computational problems of microprocessing unit associated with low speed measurement techniques are given. These contributions are experimentally tested and successfully applied to digital signal processor (DSP)- based (TMS320F28xx) ac drives used in traction applications.