A new energy recovery scheme for doubly fed, adjustable-speed induction motor drives

A new speed control scheme for a wound-rotor induction motor utilizing feedback of the slip power to the stator winding by means of taps is described. It is shown that with this feedback system, the motor can be operated over a very wide range even to slips reaching 0.75. The new concept eliminates the need for a transformer. The selection of feedback point on the stator winding, the equivalent circuit, and the main parameters of this system are discussed. Test results on a wound rotor induction motor are shown, and these indicate that this system also has good performance in addition to its potential for lower cost.>