METHOD AND APPARATUS FOR CONTROLLING CAGE-TYPE MOTOR

摘要

PURPOSE: To obtain a small and highly efficient low price brake unit by an arrangement wherein a winding is fed with a required DC current from a rectifier bridge being formed under brake state through electric control from the thyristor of a voltage converter. CONSTITUTION: Magnitude of a DC current Udc being fed from a power supply is controlled separately by interrupting current supply to a DC power supply using pairs of thyristors T3, T6 and T7, T10. At the time of brake operation, current supply to a motor 1 is interrupted by turning all thyristors off. A full- wave rectifier bridge for rectifying two phases of a three-phase main supply is then constituted and a DC current is applied to two terminals of the motor 1. In the inventive braking method, respective pairs of thyristors are controlled separately such that one pair of thyristors act as a zero diode in case of high brake torque and perform rectification continuously whereas the other pair of thyristors operate to generate a pulsating DC current.