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Hi Sven,
When the turn-off thyristor SCR2 is turned on like a switch being closed the capacitor C is placed in parallel to the main thyristor SCR1. This makes the current go through the capacitor that reverse biases the main SCR by making its anode negative when referenced to its cathode. This turns of this main SCR1. Something has to connect the capacitor in parallel to SCR1 at the moment it is to be turned off as the capacitor can't do that by its own being a passive component. Else the load will have to quickly discharge the main capacitors which will also stop the current through the thyristors.
The class A commutation puts conditions to the load that must be part of an under damped RLC tank. Then why not just have the condition to have the load discharge the main capacitors fast enough to turn off the SCRs quickly? That way the circuit of yours needs no modification except that the load impedance has to be low.
Source: https://www.electronicshub.org/scr-turn-off-methods/#Class_C_Commutation https://www.electronicshub.org/scr-turn-off-methods/#Class_C_Commutation
Regards
Ole
---In [email protected], <s.friedrich@...> wrote :
Hello Ole, it is spoken only by a parallel capacitor to scr path. Additional scr are not provided or with this control not so feasible. Or a capacitor is meant which is simply placed on the anode and cathode. Theoretically, when the scr is switched on, the capacitor should charge so that the cathode side of the capacitor heats up positively, the load would probably have to be on the cathode side. Actually, I only need to generate a fast potential change but how and dynamically depending on the impedance of the load and without electronics. I have already thought of class A commutation. Greetings Sven
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