Regarding the turn-on process of an SCR, consider the following statements:1.Latching current is the minimum anode current required to maintain the SCR in the ON state after the gate pulse is removed.2.Holding current is associated with the turn-off process.3.The gate pulse width should be sufficient for the anode current to rise above the holding current.4.Latching current is typically 2 to 3 times the holding current.Which of the statements given above are correct?

Correct Answer: B - 1, 2 and 4 only

Quick Concept Explanation

Latching current is the minimum anode current needed just after triggering so the device stays on when gate drive is removed. Holding current is the lower current threshold below which an already-conducting SCR turns off; latching current is normally higher, commonly a few times the holding current.

Exam focus: Gate pulse must persist until anode current exceeds latching current. Common trap: Do not substitute holding current for latching current during turn-on.

Statement-wise Verification

• Statement 1 - Correct.
  Latching current is the minimum anode current required to maintain the SCR in the ON state after the gate pulse is removed.
  Latching current is the minimum anode current needed just after triggering so the device stays on when gate drive is removed.
• Statement 2 - Correct.
  Holding current is associated with the turn-off process.
  Holding current is the lower current threshold below which an already-conducting SCR turns off
• Statement 3 - Incorrect.
  The gate pulse width should be sufficient for the anode current to rise above the holding current.
  For reliable turn-on, the anode current must rise above the latching current before the gate pulse is removed
• Statement 4 - Correct.
  Latching current is typically 2 to 3 times the holding current.
  Latching current is normally higher, commonly a few times the holding current.

Core Concept

An SCR is a latching thyristor. Latching current is the minimum anode current needed just after triggering so the device stays on when gate drive is removed. Holding current is the lower current threshold below which an already-conducting SCR turns off; latching current is normally higher, commonly a few times the holding current.

Formula / Key Relationship

I_L > I_H typically.

Why the Other Options Are Wrong

Option A is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 4. Option C is incorrect because it omits correct statement(s) 1. Option D is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2.

Exam Shortcut / Approach

Gate pulse must persist until anode current exceeds latching current.

Common Mistake

Do not substitute holding current for latching current during turn-on.

Quick Revision

Latching and Holding Current is linked with SCR Turn-On, Thyristors and Power Electronics. Gate pulse must persist until anode current exceeds latching current.