Basic Principles and Applications

Basic Principles

The AC input voltage is transformed by a transformer to obtain low-voltage AC power, which is then integrated into DC power through thyristors to obtain the required output voltage and current. The control circuit samples the output voltage and output current, and after closed-loop feedback, controls the phase angle at the moment when the thyristor triggers conduction through phase control to maintain stable output voltage or current.

System Architecture

Input side: Three phase AC power enters the rectifier circuit through a transformer. Rectification and voltage regulation: AC power is converted into adjustable DC power through a thyristor rectifier circuit. Output side: After filtering and stabilizing, output stable DC current. Control unit: including trigger circuit, feedback control circuit, and protection circuit, accurately adjusting output voltage and current.

Key Parameter

The input voltage is usually three-phase AC power, with an output voltage range of tens to hundreds of volts and an output current of hundreds to tens of thousands of amperes.There are two types of rectification methods: three phase bridge and double anti star, with 12 or 24 pulses. There are load regulating switches and balancing reactors, as well as incoming and outgoing line methods and control methods. Whether they are equipped with DC isolation switches and coolers, etc.

Pulse Wave

The pulse count of a thyristor power supply refers to the number of pulses output by the power supply during a complete AC cycle. The more pulses there are, the smoother the output waveform and the lower the current harmonic content. Theoretical value of 6-pulse harmonic content is 30%; Theoretical value of 12 pulse harmonic content is 15%; The theoretical value of 24 pulse harmonic content is 7.5%.

6 pulse waves:

Produced by a three-phase fully controlled bridge rectifier circuit. Output 6 pulses per cycle. High harmonic content, suitable for general industrial scenarios.

12 pulse waves:

Composed of two three-phase fully controlled bridge rectifier circuits with a phase difference of 30 degrees. Output 12 pulses per cycle. Low harmonic content, suitable for occasions with high requirements for power quality.

24 pulse waves:

Composed of four three-phase fully controlled bridge rectifier circuits with a phase difference of 15 degrees. Output 24 pulses per cycle. Extremely low harmonic content, suitable for occasions with extremely high requirements for power quality.

Structure of SCR Type Rectifier

Air Cooled Type SCR Controlled Rectifier

Water Cooled Type SCR Controlled Rectifier