Thyristor Help

[Mark34]

Hello!
I have a BT151 500R rated 500V thyristor and I want to use it in forward conducting state, so I when a current flows into the gate the anode cathode starts conducting. I need to know if the anode cathode path can support a 300V Capacitor 1000uf discharge plus a coil without frying.

 

[duke37]

Show us a schematic. The peak current will depend on the coil inductance. The power loss will depend on the frequency.

 

[Mark34]

 

[duke37]

Your circuit ill not work.

1. The gate is held positive and the SCR will behave like a NPN trnasistor which is hard on.
2. There is no DC connection across the SCR so it cannot pass current.

Normally the gate is connected to the cathode via resistor (<1k) to ensure that the SCR is not falsly triggered.
The trigger pulse shoud be short, stopping before the SCR current stops.so that the capacitor can be recharged
You will need some way of charging the capacitor.
What is it you wish to do?

 

[Gumby_Kevbo]

Placing the '2222 in series with the SCR makes no sense. SCRs were the first semiconductor devices available that would block high voltage, so people found novel ways to use them that don't really make sense nowadays with the availability of high voltage mosfets, BJTs, IGBTs etc.

The functional description of your OP sounds vaguely like the early CD (capacitive discharge) ignition systems, or a photoflash trigger, both of which SCRs were used for....so yes you can certainly use an SCR to discharge a capacitor through a coil...and that is a desirable way to use one, because if you just use an SCR switch the coil to a supply with no capacitor, then there is no way to turn it off. This is why the CD ignition system came about...it allowed you to use an SCR to trigger the ignition. Now that we have high voltage mosfets, you can just use the FET like a set of breaker points, and store the energy magnetically in the coil, and trigger the spark by switching the FET off.

 

[PAFMElb]

Never mind the health of the thyristor! Worry about the poor little 2N2222 in the path. That's got a 600mA max continuous current, so estimate 10 times that for a peak current and even assuming a low duty cycle you still need to consider if that is the right transistor for the job. As others have said, the current being handled depend much on the coil / capacitor combination. I understand you have not shown the full circuit, but what is there is suspect.
Why a pot for the phototransistor load? Why a photo coupler at all, when there is no isolation shown? Why is the SCR cathode floating? Why is the gate permanently tied to the 9V supply? When the 2N2222 turns on you are shorting the 9V supply to ground via the gate-cathode path.

Did you mean for the 2N2222 to shunt gate to ground rather than be in the thyristor discharge path, and for there to be a limiting resistor from gate to 9V instead of the gate connecting directly to the 9V supply?