Patent ID: 7042194

Claim:
A controller for a wound-rotor induction motor comprising: a first voltage-type converter connected to a secondary winding of a wound-rotor induction motor driven by an AC power supply; a capacitor for smoothing DC output voltage from the first voltage-type converter; a second voltage-type converter for supplying the A.C. power supply with a regenerated power from the output of a D.C. power of the first voltage-type converter; a speed detecting means for detecting a speed of the wound-rotor induction motor; a current detecting means for detecting the secondary current of the wounded-rotor induction motor; a voltage detecting means for detecting the DC voltage applied to the capacitor; a speed control means for controlling the speed detected by the speed detecting means in response to a referential speed, and for outputting a secondary current as a referential current; a first PWM control means for controlling the current output from the current detecting means in response to the referential current, and for outputting a voltage signal by witch self extinguishing type switching elements of the first voltage-type converter are controlled by pulse-width modulation; and a second PWM control means for controlling a voltage output from the voltage detecting means in response to a referential voltage, and for controlling by PWM self extinguishing type switching elements constituting the second voltage-type converter; wherein the first PWM control means is constituted to control an ON-OFF ratio of a period in which the first voltage-type converter makes short circuits of the secondary winding of the wound-rotor induction motor.