Designing Thyristor(SCR) Gate Driver Circuit.

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Scab!

I can see how one could use SCR to control the battery charging circuitry but since a SCR cannot be turned OFF I do not see how to use it to produce the three phase power output when running on battery power. I suspect that there are some clever designs using a resonating circuit that does allow SCR to turn OFF. Good luck in your search.

Yes, a SCR can be turned OFF. It is required, though, another SCR.

A dc conducting SCR is turned off by dumping a capacitor across it to reduce the conduction to near zero long enough for the SCR to shut down. Its a brute force method used in many older Xray machines. They are typically conducting 50A or more at 50+volts, you can imagine the cap energy to quench that SCR.

Quenching circuits to accomodate 3 phases at 60hz will require very large energy waste. Better off to control the current flow through IGBT's.

Redfred, I believe you are thinking DC. In AC the SCRs will turn off every cycle on their own when the sine wave crosses zero. The gate circuit then has to re-fire them. The OP is asking about a static transfer switch on the AC side.

Absolutely, 100% correct. I am thinking about DC. Since this thread discusses a UPS which likely includes a DC producing battery, I still believe my point is valid. I presume that this could be an inertial drive UPS system where only AC motors and generators existed. Any inertial drive UPS design company would certainly have engineers that know to look at the recommended application notes of their suitable SCR. The mechanical engineering of such a system is the hard part. The electrical engineering is the easy part.

Somebody that doesn't know how to look for application notes probably intends to use a battery and therefore nearly all of engineering complications will be electrical engineering. As recent threads here show, getting a sine wave output from a DC source using just semiconductor switches is not as easy as many think.

I need to expand my view. I am using the SCRs in my Static Transfer Switches(STS) which switches between UPS and Line. So i needed a help in Driving this SCRs. . .

Karthikhp12, are you looking to re-invent the wheel here by building your own from scratch? Because there are many companies out there who sell inexpensive gate firing boards used for this exact purpose. Most people who make UPS systems with STS options just use pre-made boards, your sales volume would have to be incredibly large to justify the expense to develop, test and build your own.

anti parallel? SCR can be used in SCS or transistor mode below hold current.