Sensorless speed measurement of induction motors using an adaptive frequency-tracking algorithm

Sensorless speed estimation is of importance to a variety of industrial applications where speed information is required. Standard shaft-mounted speed transducers are the commonplace solution to speed estimation. However, they add complexity to a motor and wear with time. This paper presents a novel technique of determining speed from eccentricity harmonics within the stator current. The presented technique provides a computationally efficient, real-time sensorless speed measurement method based on a frequency-tracking signal processing algorithm. The proposed technique is shown to be advantageous in that it is capable of providing precise real-time speed estimation through changes in mechanical load and source frequency changes. The developed technique is suitable for all adjustable drives including direct torque control (DTC) drives.