Development of synchronous torques in asymmetrical rotor induction machines

Results of an experimental investigation on an asymmetrical rotor induction motor in developing synchronous torques at any speed other than the `synchronous speed¿ are reported. It is shown that such torques can be developed at any speed wr electrical rad/s by injecting additional balanced stator voltages (of proper sequence) of frequency f¿2fr where f is the fundamental line frequency andfris wr/2¿. The investigation throws light on the feasibility of using these phenomena for variable speed drives.