Working of a Rectifier

The rectifiers are either oil immersed or air cooled. In air cooled rectifiers, heat in removed by natural convection of the air. Mineral oil is used in oil immersed rectifiers. They are are often used for marine environment applications and in the presence of corrosive vapors.

Operation of a Single Phase Bridge Rectifier:

The following figure shows the operation of a single phase bridge rectifier. In the first half cycle of AC current, the direction of current flow reverses 120 times per second for the 60 cycle AC current.

• The current originates positive T1 on the secondary winding.

• The current is blocked by D3 (silicon diode).

• The current flows through the diode D1 as shown in the figure. It follows the path (3) in the figure and through the diode D4, it enters the negative terminal T2.

• In the next cycle 1/120 of a second later, the direction reverses and follows the path shown in the figure.

• It is blocked by diode D4 and flows through D2, follows the path 3 through D3, in the same direction as before.

• The load therefore receives continuous energy in the form of pulses. The current paths are called 'legs'.

Rather than a single phase rectifier, the three phase bridge is the most common circuit for rectifiers operated from single phase bridges; however, each bridge shares a pair of rectifier circuits.