Q.Explain the construction and working of SCR full wave rectifier with RC triggering circuit.

The SCR full-wave rectifier with RC triggering uses a single thyristor together with a diode bridge so that both halves of the ac are made unidirectional, and the RC network fires the SCR at an adjustable firing angle in every half cycle. …

[!TLDR]

Single SCR plus diode bridge rectifies both halves; the RC network fires it at $\alpha$ each half cycle, giving full-wave output with $V_{dc}=\frac{V_m}{\pi}[1+\cos\alpha]$.

Construction: The ac supply feeds a transformer whose secondary (terminals A, B) supplies a four-diode bridge rectifier. The bridge output is a unidirectional (rectified) voltage that is passed through the load resistor $R_L$ and a single thyristor (SCR). The RC triggering circuit (series resistor $R_1$, variable resistor $VR_1$, capacitor C and diodes $D_1$, $D_2$) is connected to the diode-rectifier output, so the capacitor voltage follows the rectified waveform.

Working: The diode bridge converts the ac into a unidirectional current through the thyristor, i.e. both halves of the supply now drive the SCR in the same direction. In each half cycle the capacitor voltage rises and, when it reaches the trigger level, it supplies enough gate trigger current to fire the thyristor; the thyristor then conducts and the voltage appears across the load. Because the input to the SCR is unidirectional in both halves, conduction occurs in every half cycle, giving full-wave rectification.

Control: The firing angle read from the load-voltage waveform is …