Applications of the FFT to the speed measurement of inverter fed induction motors
Azzeddine Ferrah, K.J. Bradley, Greg M Asher · 2003
An alternative to the analog techniques and devices used in detecting the speed of induction motors in adjustable-speed drives is presented. The method involves digital processing of one stator phase current in order to retrieve the speed information contained in the slot-ripple harmonics, using FFT-based spectral analysis. A noninvasive digital speed detector, suitable for steady-state operation, was developed. The detector is designed around an Intel/80386-based microcomputer. Its performance with and without load over a wide range of speeds is reported.>