Controlling the speed of an induction motor by resonating the rotor circuit

The possibility of obtaining various torque-speed characteristics from a wound-rotor induction motor by operating such a motor close to its rotor resonance is described. It is shown that, by the use of reactive rotor networks, high starting and braking torques may be obtained. An induction motor operating with this proposed technique of speed control also reacts favorably to nonsinusoidal supply voltages and has an improved power factor. No auxiliary machines or power supplies are required and any slip ring induction motor of conventional design can be used.