A Novel E/F Controller for Squirrel Cage Induction Motor Based on Rotor Flux Orientation

In this paper, a novel E/F control algorithm is proposed for the three-phase squirrel cage induction motor based on its rotor-flux-oriented model. The proposed scheme is meant for a current-sensor-less induction motor drive operating with speed feedback, and it offers an attractive solution to various problems associated with the traditional V/F type of induction motor drive unit. The speed control loop of the proposed scheme emulates the back-electromotive force of the motor and not the terminal voltage, and therefore, the decrease in the magnetizing flux in the low-speed region is overcome. In addition, the lowspeed operation becomes possible with the proposed E/F scheme, which is difficult to realize with the traditional V/F motor drive unit. Moreover, since the proposed strategy is based on the rotorflux-oriented model of the motor, it gives performance that is on par with a vector-controlled induction motor drive unit, and the control algorithm is simplified. The proposed scheme is validated using simulation and verified using a fractional horse-power squirrel-cage induction machine coupled to a separately excited DC machine. To emphasize its performance, it is also compared with the vector-control algorithm.