ABSTRACT
This chapter discusses different circuit topologies and operational characteristics of ac to dc power conversion, which are commonly labeled as controlled rectifiers. These power converters convert existing ac supply to dc voltage of controlled amplitude. Silicon-controlled rectifiers (SCRs) are employed as switching elements, and commutation of these SCRs takes place with the help of input line voltage, thus making additional commutation circuits unnecessary. These converters are classified as single-phase and three-phase converters based on the availability of single-phase or three-phase power supply. Such ac/dc converters are also categorized as semi-converters and full converters; semi-converters are single-quadrant converters, whereas full converters operate in two quadrants of V-I (voltage-current) diagram. Line-commutated ac/dc converters are used for variable speed operation of dc motors, high-voltage dc transmission (HVDC), battery charging, and front-end feeders to inverter circuits.
