Reactive Power Compensating Device for High Power Windings Rotor Induction Motor

This papers present how a capacitive voltage source is connected in series to the rotor of induction motor to improve power factor, reduce stator current, and improve efficiency and ability of overloading. The principle of the reactive power compensating device for windings rotor induction motor based on AC-AC cycloconverter is described. A single phase to three phases AC-AC cycloconverter is adopted in order to produce capacitive voltage, which make the circuit simple and capacity of transformer much decremented. Using 89S52 sing-chip microcomputer as the control core. The system is capable of the protecting functions of over current, over temperature, lack of phase and running state's control of the motor. The system was tested on a JR138-8 motor. The result shows that the power factor is over 0.95 and the current of the stator reduces over 15%. The system can be widely applied to large and medium-sized winding asynchronous motors in the fields of building materials, chemical industry, chemical fertilizer, paper making, pharmacy, metallurgical industry.