Hello All,
I am making a 3phase static transfer switch using triac.The triac which I used is Bta-12 800b.Actually I want to switch load between 3phases in my home.The problem is whenever I switch my circuit on ,the triac got ruptures and there is a blast.I am working on resistive load so I haven't put snubber.Can u plz tell the issue.Attached is the schematic of my circuit
Thanks

 

Here is the schematic

 

You must be very, very sure that only one triac is ever switched on. The triac which is switched on will continue to conduct until the end of the cycle even if the control signal is removed so you need a delay between switching one off and switching the next one on.

 

You must be very, very sure that only one triac is ever switched on. The triac which is switched on will continue to conduct until the end of the cycle even if the control signal is removed so you need a delay between switching one off and switching the next one on.

I have to agree. If two TRIACS are turned on at the same time, you're basically creating a short circuit. This is three phase we're dealing with here, so assuming you're always supplying power to the RED, YELLOW, and BLUE phases, they would most likely be at different voltage levels. So if the TRIAC of RED PHASE and YELLOW PHASE are both activated, RED PHASE would be at a different voltage potential than the YELLOW PHASE and when there is a connection with almost no resistance between different voltage potentials, a high amount of current can go through them. Thus a short circuit.

 

You must be very, very sure that only one triac is ever switched on. The triac which is switched on will continue to conduct until the end of the cycle even if the control signal is removed so you need a delay between switching one off and switching the next one on.

Thanks 4 reply.But I am giving a delay of 2s between switching so it won't be a issue

 

Where does that "Ground" connection on the left go to?
According to your circuit that lead is hot with the load voltage when the TRIAC fires.

 

If you're giving a 2second delay, then why dont you use relays instead??