Asymmetrical controlled rectifier with high power factor - has forced commutation on two phases of three-phase bridge comprising thyristors

摘要

The three phase bridge rectifier feeding a dc load (1, 2) has thyristors in four arms (5-8) and diodes (3, 4) in the remaining arms. The thyristors are provided with forced commutation circuits comprising auxiliary thyristors (19-21) commutating capacitors (9-12) and their charging circuits (17, 18, 13-16). Control is by triggering the main thyristors at the voltage crossover point and then commutating them off to give the required output voltage. The combination of controlled and uncontrolled elements in the bridge combined with forced commutation and capacitors larger than necessary for commutation only enables the rectifier to operate with nearly unity power factor and low harmony distortion.