Explain thyristor gate drive circuit.
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Answer :
Thyristor Gate Drive Circuit:
The thyristor can be turned on by pulse voltage signal at gate terminal and it does not require continuous drive signal like the transistor. The gate circuit is used for triggering or firing thyristor this circuit called triggering circuit or firing circuit. If the gate signal voltage exceeds gate triggering voltage then thyristor turns on. In case of resistive load, the single sharp rising pulse is enough for triggering but in case of inductive load the pulse should be slightly higher than gate triggering current is applied till the successful triggering takes place. The thyristor is used for high voltage levels and there are two circuits one is control circuit and one is triggering circuit. If the thyristor is used for high power applications then the triggering circuit and control circuit should be isolated from the power circuit. This isolation is done to avoid the high transients of voltage and current. Thyristor gate drive circuit may be non-isolated or optically isolated or it may be transformer coupled gate drive circuit. If the firing circuit or triggering circuit provide required minimum gate voltage and gate current then the thyristor conducts properly.