AC-to-DC Rectifiers - Introduction

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC) which flows in only one direction.
There are two types of rectifiers:

• Uncontrolled rectifiers, essentially made with diodes, are used when the output voltage does not need to be adjusted.
• Controlled rectifiers, whose output voltage can be variable, include thyristors or sets of diodes and thyristors.

In a rectifier circuit, the output current is always the absolute value of the input current.
However, the shape of the output voltage depends on both the shape of the input voltage and the nature of the load.

In this laboratory, the single-phase Diode Bridge (or Graetz Bridge, which is composed of four diodes), the three-phase diode bridge (which is composed of six diodes), and the three-phase thyristor bridge (which is composed of six rectifiers) are studied.

Figure 1: Single-Phase Diode Bridge Rectifier

Figure 2: Three-Phase Diode Bridge Rectifier

Figure 3: Three-Phase Thyristor Bridge Rectifier