Ramp Triggering and Open-Loop Control

Correct Answer

A — ramp triggering, open loop control

Explanation

A synchronized UJT relaxation-oscillator scheme develops a ramp/sawtooth synchronized to the AC supply and fires the SCR at a controllable point. If firing angle is adjusted only by varying a resistor without output feedback, the control is open loop.

Key Concept

Ramp Triggering and Open-Loop Control

Exam Point

UJT synchronized firing → ramp; resistor-only adjustment → open loop.