Thyristor & Power Control Circuits Unit 5 – UJT Triggered SCR Power Control
UNIT 5 – UJT TRIGGERED SCR POWER CONTROL
UNIT OBJECTIVE
At the completion of this unit, you will be able to use a unijunction transistor (UJT) as the trigger
device for an SCR by using a typical UJT-SCR circuit.
UNIT FUNDAMENTALS
This is the symbol for a unijunction transistor (UJT). The UJT has 1 PN junction and 3
terminals. In this unit, you will use the UJT to control the conduction angle of an SCR.
In this circuit, a UJT phase control is used with a half-wave rectifier.