Question

Difference between fully controlled and half controlled rectifier

Answer 1

In power circuits, a typical half-controlled rectifier is a bridge rectifier that uses two SCR's and two diodes for a single phase bridge, and 3 SCR's and 3 diodes for a three-phase bridge. Half-controlled rectifiers were used commonly when the SCR's were much more expensive than diodes. A half controlled rectifier (full bridge) can only control power flow in a single quadrant. 

A full-controlled rectifier uses SCR's for all control elements - 4 in a single phase bridge, 6 in a three-phase bridge. Full controlled rectifiers can control power in quadrants 1 and 2. Also, if a second bridge is added for 4 quadrant control, a fully controlled bridge must be used, as one has to be completely turned off when the other is firing.

Answer 2

difference between fullycontrolledrectifier