Merits And Limits of Sensor-Less Flux Estimation of Induction Motor

The emphasis of research on induction motor drives has been on sensorless vector control which eliminates flux and speed sensors. Also, the development of effective speed and flux estimators has allowed good rotor flux-oriented (RFO) performance at all speeds except those close to zero. This paper evaluates documented schemes for sensorless drives, and discusses the merits and limits involved in selecting a particular scheme. But main focuses is on the observer-based flux estimation, by injecting high frequency test current. It is the newly emerging control scheme for all kind of flux operated system, especially for standard induction motors around zero speed. This scheme is free of integration and in relation to the demand of a high performance at very low frequencies. The determination is based on saturation effect using high frequency magnetizing current