Thyristor as a triac

[Ramesh Adhikari]

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.

 

[(*steve*)]

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]

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]

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?

 

[WHONOES]

A proper circuit diagram will be more illuminating.