Latching current for an SCR is 100 mA, a dc source of 200 V is also connected to the SCR which is supplying an R-L load. Compute the minimum width of the gate pulse required to turn on the device. Take L = 0.2 H & R = 20 ohm both in series

To determine the minimum width of the gate pulse required to turn on the SCR, we can use the properties of the R-L circuit.

1. Circuit Components:

– DC Supply Voltage (V) = 200 V

– Resistance (R) = 20 Ω

– Inductance (L) = 0.2 H

– Latching Current (I_L) = 100 mA = 0.1 A

2. Total Circuit Resistance:

The initially applied voltage across the R-L load when the SCR is turned on can be calculated using Ohm’s law:

[

I = frac{V}{R}

]

but to find the time constant for the circuit and define the time to reach the latching current, we need to consider the voltage across the inductor and the time constant (tau) of the circuit defined by:

[

tau = frac{L}{R}

]

Plugging in the values:

[

tau = frac{0.2 , text{H}}{20 , Omega} = 0.01 , text{s} , (10 , text{ms})

]

3. Voltage Across the Load:

The voltage across the load at time (t) can be defined by the formula for an R-L circuit:

[