Need Help with High-Power SCR Triggering

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Thread Starter

PC Pete

Joined Nov 11, 2011
G'day all!

I've started to need some very high-powered SCRs ("puck" or P30T package) for use in a gauss gun prototype.

The SCR I'm using is a TR956-250F-12. The spec sheet (which is in Russian, komrad) seems to imply a Vgt/Igt value of 2.0/400... which means it requires 2V@400mA (if I'm reading this right!).

However... Supplying 2-9V@400mA doesn't seem to be helping the darn thing trigger (this is with a "proof of concept" supply of 355VDC@250A or so).

I've tested all 3 units, and none of them trigger with this gate voltage/current.

Am I missing something important?

FYI, I'm using the anode connected to +350V, Cathode to coil, coil to ground, and a current-limited supply connected between the cathode lead (negative) and gate (positive).

All devices seem to test OK with a multimeter. No shorts, no opens, apart from what I'd expect.

Any advice would be greatly appreciated!



Joined Oct 26, 2011
2V and 400mA seems typical for such a device.

The ideal way to turn it on is to blast it (gate to cathode) from a 0.47uf cap charged to 12V with a series resistance of 10Ω--resulting current will be in the order of 1A or so.

Make sure that the puck is squashed in a heatsink assy, because the wafer inside the package can float and not make contact.

Also, the circuit is more friendly if the load is in series with the anode rather than the cathode--this puts your triggering circuit at ground potential thus preventing dv/dt issues from bothering your triggering.


Joined Apr 2, 2009
I don't think this topic is Welcome here.

But I do welcome you to AAC.

Better read TOS.

We'll leave this till a MOD approves it.


Joined Apr 5, 2008

I am closing this thread as it violates AAC policy and/or safety issues.

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