A three phase full wave controlled rectifier is a power electronic circuit used to convert three phase alternating current (AC) into direct current (DC). It provides higher output voltage compared to a single phase rectifier and has better electrical characteristics. Or A Three-phase Full-wave Rectifier converts three-phase alternating current (AC) input into direct current (DC) output using semiconductor diodes or controlled switches like thyristors. It provides a smoother, more continuous DC output compared to single-phase rectifiers, making it ideal for industrial applications.

In this article, we will discuss the working, output waveform, advantages and applications of a three phase full wave controlled rectifier. The information in this article helps you extensively in your SSC JE Electrical and GATE Electrical preparation journey.

What is Three Phase Full Wave Controlled Rectifier?

A Three-phase Full-wave Controlled Rectifier is a power electronic converter that transforms three-phase alternating current (AC) into direct current (DC) by using controlled semiconductor switches, typically thyristors (SCRs). Unlike uncontrolled rectifiers, controlled rectifiers offer the capability to regulate the output voltage by adjusting the firing angle (α) of the thyristors, allowing precise control over the DC output voltage and current. A three phase full wave controlled rectifier consists of three single phase full wave controlled rectifiers connected in such a way that all the three phase voltages are used for DC power production. Each single phase full wave controlled rectifier contains two thyristors or transistors which act as electrically controlled switches. When gate pulses are applied to thyristors, it starts conducting immediately and allows current to flow in one direction only.

Let's understand the working with the help of conduction cycle: The thyristors are numbered in the circuit diagram corresponding to the order in which they are triggered. The trigger sequence (firing sequence) of the thyristors is 12, 23, 34, 45, 56, 61, 12, 23, and so on. 

Fig-Circuit Diagram Of Three phase Full Wave Rectifier

This ensures that the load receives the positive half of all the three phase voltages successively, thereby obtaining a continuous unidirectional DC output.

• The Average Output Voltage Of Three phase Full Wave Rectifier is calculated as

The RMS value of the output voltage is 

Three Phase Full Wave Rectifier Conduction Waveform

The following waveforms illustrate one cycle of conduction:

Fig-three phase full wave controlled rectifier waveforms

As seen in the diagram, the load voltage VLoad is the continuous summation of the three phase voltages which is a smoothened waveform without any discontinuities. 

Application of Three Phase Full Wave Controlled Rectifier

Some Important applications of a three phase full wave controlled rectifier include:

• DC drives: Used in variable speed drives and controllers for applications like metal processing machines, paper mills, cranes etc.
• Traction power supplies: Used in electric locomotives, underground metros and trams to convert AC overhead lines/third rail to DC for traction motors.
• UPS systems: Uninterruptible power supplies used in data centers, telecom switches, hospitals employ a 3-phase rectifier for battery charging.
• Induction heating: Used to heat metals by electromagnetic induction for processes like tube bending, pipe welding, heat treatment of steel.
• Electroplating: Provides DC for electrodeposition of zinc, copper, chromium coatings in industry.
• Solar inverters: Converts the DC from solar panels to AC for feeding into the grid or loads.

Advantages Of Three Phase Full Wave Controlled Rectifier

• The key advantages are;
• Higher and more stable DC output voltage
• Lower ripple factor
• Smaller filter components compared to single phase rectifiers. 

Disadvantages Of Three Phase Full Wave Controlled Rectifier

The disadvantages include 

Higher conduction losses due to use of more thyristors and complexity in gate drive circuitry.

This article summarises all the information related to three phase full wave controlled rectifier, which helps propel your preparation for various AE/JE and ESE examinations. You can visit the Testbook app to keep yourself updated with all the exam-oriented information related to the upcoming examination, like SSC JE, GATE, ESE, RRB JE, and state AE/JE Exams.