In the following Crowbar Network the Zener Diode is the 1N75

In the following Crowbar Network the Zener Diode is the 1N759(See Data Sheet Posted to Bb). Assume SCR Junction 1.4 V and Typical Values. VGT IGT IH Supply Voltage that will trigger the SCR Crowbar Fuse rating that will protect the SCR (Minimum Value)

Solution

Dear Student:

Just follow the below given points:

1. The connection of a SCR will be parallel to supply voltage, at this situation voltage across the SCR is same as that of supply voltage there is element to dissipation of energy.

2. From the data sheet Vgt = 0.65V (typically). this can be obtained by connecting 100ohms resistor across the gate circuit with in series with zener diode (applied voltage 12V minimum).

3. From the data sheet Igt = 25 micro AMPS.

4. Holding typically 0.5 milli AMPS.

5. Supply voltage typically 12.7V is required to activated the circuit.

6. This will be depends upon load. if you choose load 10 ohms and supply voltage 12.7V the rating of fuse the you can choose 1.5A.

if you have any doubts regarding to the data just open the below link follow the data.

http://www.onsemi.com/pub_link/Collateral/MCR8S-D.PDF

if you want you updated simulation diagram comment me this question

Thankyou.