A wound-rotor induction motor closed-loop control system

A subsynchronous cascade system implemented in the laboratory permits motor speed control by using two cascade-connected governors (the first for speed and the second for current), to fire the inverter of the rotor DC link. A diode bridge is connected to the rotor terminals and the thyristorized inverter is connected to the line by means of an autotransformer. This system makes it possible to recover the rotor energy when compared to the conventional rotor resistance variation, that causes an energy dissipation in the rotor circuit. The torque speed curves have been traced by modifying the inverter firing angle and the load torque. These curves are polemical in the literature and laboratory tests permit the determination of their real aspect. Current and speed are registered, when a load disturbance torque takes place, to confirm the speed regulation and the current. >