Basic Principle: AC input voltage is transformed by a transformer to produce low-voltage AC power, which is then regulated by silicon-controlled thyristors (SCRs) to DC power, resulting in the required output voltage and current. A control circuit samples the output voltage and current, and after closed-loop feedback, uses phase control to control the phase angle at the moment the SCR is triggered to conduct, maintaining a stable output voltage or current.

System Architecture: Input Side: Three-phase AC power passes through a transformer and enters the rectifier circuit. Rectification and Voltage Regulation: The SCR rectifier circuit converts the AC power into adjustable DC power. Output Side: After filtering and voltage regulation, a stable DC current is output. The Control Unit: This includes the trigger circuit, feedback control circuit, and protection circuitry, precisely regulating the output voltage and current.

Key Parameters: The input voltage is typically three-phase AC, the output voltage ranges from tens to hundreds of volts, and the output current ranges from hundreds to tens of kiloamperes. Rectification methods include three-phase bridge and double reverse star. The pulse count is 12 or 24 pulses. The circuit features an on-load tap changer and balancing reactor, as well as input and output wiring and control methods. The presence of a DC disconnector and cooler is also covered.

Rectification Method

Three-phase Bridge Rectification: Three-phase bridge rectification typically uses a standard three-phase transformer, with the secondary windings connected in a three-phase star or delta configuration. Rectification Elements: Six thyristors (SCRs) or diodes are used to form a three-phase full-wave rectifier bridge.

Double reverse star rectification: Double reverse star rectification is available with or without balancing reactors, also known as the three-phase five-leg design. This requires a specially designed transformer with two secondary windings, each connected in a three-phase star configuration with a 180-degree phase shift. Rectification Elements: Each star-connected three-phase winding undergoes half-wave rectification using thyristors (SCRs) or diodes. To balance the current between the two rectifier circuits, a balancing reactor is usually added on the DC side.

24-pulse double-reverse star-type thyristor rectifier outline diagram