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Thyristor as a triac

Ramesh Adhikari

Apr 6, 2018
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Apr 6, 2018
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Hi, I have a thyristor with the connection as in this thyristor and i am trying to use it as a traic. So i shorted terminal 2 and 3. terminal 1 and 7 are already connected as in this thyristor.Also i have shorted both the gate (4 and 6).Now i want it to act as a traic with terminal M1(7) and M2(5) and gate(wire that has connected 4 and 6). Will this work?

Problem: When i simply gave supply to 7 and 5 with a blub connected between them(no pulse signal to gate) the blub glow. Then I checked the individual gate terminal with my tester i saw a phase indication present in gate terminal 4. That was causing the blub to glow. But i expect no phase indication in both gate since i want it to be controlled through my pulse signal. What actually is happening in this case and how can i solve it? Note my connection is same as in second picture.Thank you.Thyristor-Diode-Power-Module-Easy.jpg
triac-equivalent-function.gif
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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You will require a different polarity signal to turn on one scr vs the other. (I.e. in a single, but different quadrant for each).

In contrast, triacs can often be triggered in 4 quadrants.
 

WHONOES

May 20, 2017
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You have to drive each gate individually. The best way and also get galvanic isolation is to use a small pulse transformer between gate and cathode. This will also allow you to get the opposite polarity required. Sometimes, the trigger pulse is constructed as a series of pulses for the required conduction period. This ensures that each half of the circuit will remain on for the conduction period.
Alternatively, an opto-isolator could be used in a similar fashion. This has the advantage that energy from the SCR circuit will not be reflected back into you drive circuit.
 

Ramesh Adhikari

Apr 6, 2018
2
Joined
Apr 6, 2018
Messages
2
You have to drive each gate individually. The best way and also get galvanic isolation is to use a small pulse transformer between gate and cathode. This will also allow you to get the opposite polarity required. Sometimes, the trigger pulse is constructed as a series of pulses for the required conduction period. This ensures that each half of the circuit will remain on for the conduction period.
Alternatively, an opto-isolator could be used in a similar fashion. This has the advantage that energy from the SCR circuit will not be reflected back into you drive circuit.
Thank you so much, Will this connection work?pulse trer.jpg
 

WHONOES

May 20, 2017
1,217
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A proper circuit diagram will be more illuminating.
 
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