Thyristor gate trigger

Thread Starter

NANCHI

Joined Sep 13, 2017
11
Hi everyone,
Please I have 2pcs of semikron skkt 250/16e thyristors module, and I need a circuit that can trigger the gates, if 0......10dc is inputted into the circuit.
Thanks
 

Alec_t

Joined Sep 17, 2013
12,824
The control circuit for the triacs will depend on the load you intend to drive. Some loads tolerate phase-controlled switching, others might not. If the load is a resistive heater with high thermal inertia then burst-mode control is usually appropriate.
Be aware that peak mains voltage will still be present, even if the overall RMS voltage is reduced by thyristor switching.
 

Thread Starter

NANCHI

Joined Sep 13, 2017
11
The control circuit for the triacs will depend on the load you intend to drive. Some loads tolerate phase-controlled switching, others might not. If the load is a resistive heater with high thermal inertia then burst-mode control is usually appropriate.
Be aware that peak mains voltage will still be present, even if the overall RMS voltage is reduced by thyristor switching.
The load am controlling is an inductive load, I want to feed the input of a step down transformer.
 

Thread Starter

NANCHI

Joined Sep 13, 2017
11
What are you connecting to the secondary of this transformer?
The output of the transformer is used for annealing of copper conductor. I.e the output is short circuited by the conductor that passes through a roller at s a speed there by heating the conductor for annealing to be achieved.
 

Ian0

Joined Aug 7, 2020
5,213
You can try this.
You can trigger two back-to-back SCRs with a single opto-triac. You might not even need the cathode-gate diodes as most big SCR seem to have a low value resistor (10Ω or so) integrated between gate and cathode.
Although it's a resistive load, I'd still recommend a snubber. either across the thyristors or across the transformer.
For the 0-10V trigger circuit the LM317 should be set to give about 10.5V output, and the small signal transistors are your favourite small signal transistor (BC547/BC847/BC557/BC857/2N3904/2N3906 etc)
The only critical capacitor is the 47nF.
The Opto Triac is the random phase variety (obviously)
The small transformer is >3VA 12-0-12V or 15-0-15V (you may already have one in circuit), with the primary connected to the same mains as your power transformer.2A911992-42CE-4261-B1DA-4EDEB4C47E2C.jpeg
[EDIT] The first NPN transistor should have a 1N4148 diode with its cathode to the transistor base and its anode to the emitter, to protect its base-emitter junction from reverse polarity.
 

Thread Starter

NANCHI

Joined Sep 13, 2017
11
You can try this.
You can trigger two back-to-back SCRs with a single opto-triac. You might not even need the cathode-gate diodes as most big SCR seem to have a low value resistor (10Ω or so) integrated between gate and cathode.
Although it's a resistive load, I'd still recommend a snubber. either across the thyristors or across the transformer.
For the 0-10V trigger circuit the LM317 should be set to give about 10.5V output, and the small signal transistors are your favourite small signal transistor (BC547/BC847/BC557/BC857/2N3904/2N3906 etc)
The only critical capacitor is the 47nF.
The Opto Triac is the random phase variety (obviously)
The small transformer is >3VA 12-0-12V or 15-0-15V (you may already have one in circuit), with the primary connected to the same mains as your power transformer.View attachment 245219
[EDIT] The first NPN transistor should have a 1N4148 diode with its cathode to the transistor base and its anode to the emitter, to protect its base-emitter junction from reverse polarity.
Thanks for your response , but I don't know what point to input 0...10dc, the point that would trigger the thyristors gates
 

Ian0

Joined Aug 7, 2020
5,213
Thanks for your response , but I don't know what point to input 0...10dc, the point that would trigger the thyristors gates
[edit] The unconnected pin on the LM393 is the 0-10V input.
The LED on the LM393 output is the LED in the opto-triac.
 
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