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back to back scr circuit

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kamal3498

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Hello guys
I have used the following image circuit to drive two back-to-back SCR.
i use two scr, D1 & D2 (1200V, 25amp).
and the my load is inductive.
when I use this circuit the D1 SCR is short.
can anyone help me?
thanks.

Capture1.PNG
 
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Hi everyone,

I’m working on a circuit that involves an EL3063 optocoupler and a 25TTS12 SCR. The circuit is designed to control an AC load, and I've included a schematic (attached below) for reference.

Problem:The issue I’m facing is that the SCR labeled D2 in the schematic keeps getting damaged after a short period of use. I’m not sure what’s causing this problem, and I would appreciate any guidance.

Circuit Details:
  • ZCD Optocoupler: EL3063
  • SCR: 25TTS12 (D2)
  • Gate Resistor (R7): 330 ohm, 1/2W
  • Snubber Circuit: 19.5 ohm, 4W resistors(39 ohm 2W parallel) and 0.1uF, 310VAC capacitor (R16, R3, D1, C1)
  • Other Components: As shown in the attached schematic
Symptoms:The SCR (D2) seems to work initially, but after some time, it gets damaged. I’ve already tried replacing it, but the problem persists.

What I’ve Tried:
  • I’ve checked for any obvious short circuits or incorrect connections.
  • Replaced the SCR with a new one, but it also got damaged after some time.
  • Verified that the gate resistor value is correct.
Request:Could someone help me identify why the SCR is getting damaged? Is there something wrong with the component values or the circuit design? Any suggestions or advice would be greatly appreciated.
 

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FvM said:
My load is ...
Click to expand...
My load is 0.5HP motor auxiliary winding with starting capacitor 80-100uf 300vac. i use the circuit for connect starting capacitor for 3 second to auxiliary winding. the back to back scr use as ac switch.
 
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kamal3498 said:
My load is 0.5HP motor auxiliary winding with starting capacitor 80-100uf 300vac. i use the circuit for connect starting capacitor for 3 second to auxiliary winding. the back to back scr use as ac switch. Could someone help me identify why the SCR is getting damaged?
Click to expand...
 
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