The regenerative action does not take place in which type of triggering method to turn on the SCR?

Solution:-
There are several methods to turn on the SCR-

→ Forward voltage triggering

→ Gate triggering

→ \(\rm \frac{dv}{dt}\) triggering

→ Thermal triggering

To understand the process of regeverative action in SCR we will have to understand the two transistor model of SCR-

For Q1

Ic1 = α1 I∈1 + ICBO1

Ic2 = α2 I∈2 + ICBO2

∴ Ic1 + Ic2 = α1Ia + α2Ik + ICO

Where, IC0 = ICBO1 + ICBO2

Ic1 + Ic2 = IC1 + IB1 = IE1 = Ia

Ik = IE2 = IB2 + IC2 = Ig + (IC1 + IB1) = Ig + Ia

∴ Ia = = α1Ia + α2Ik + ICO

Ia - α1Ia - α2Ia = α2Ig + ICO

\(\rm I_a=\frac{α_2 I_g+I_{CO}}{1-(α_1+α_2)}\)

If Ig ↑ ⇒ Ia ↑ ⇒ IE1 ↑ ⇒ α1 ↑

Ig ↑ ⇒ I_k ↑ ⇒ IE2 ↑ ⇒ α₂ ↑

→ When the SCR is forward bias, and a small Ig given to it. then it will help in establishing the regenerative process within the SCR.

After this regeneration process establishes, the gate current can be removed. This can be ensured when anode current (Ia) is greater than a prespecified value known as holding current.

→ High forward voltage triggering method will not help in regeneration action instead it will lead to breakdown of junction J₂.

therefore, correct option is (2)