tom66
Junior Member level 1
I wish to switch a large, possibly inductive load AC mains (up to 250Vac or 440Vac) using SCRs.
I could use a TRIAC but these present problems in switching off with inductive loads and require snubbers (except the snubberless TRIACs) but for the moment TRIACs are not an option. It is simpler to use an SCR in this application. SCRs also seem to be rated for much higher loads at lower cost, even when two are required for every TRIAC.
I have read that a TRIAC is very similar, though not identical, to two SCRs in inverse parallel with the gates joined together. So I whipped a simulation up and I found that the circuit would always conduct in reverse and triggering the gate made it conduct forwards and backwards. Significant current (5 amps!) flowed through the gate terminal into the AC source or load. So I'm confused as how to control inverse-parallel SCRs.
Thanks,
Tom
I could use a TRIAC but these present problems in switching off with inductive loads and require snubbers (except the snubberless TRIACs) but for the moment TRIACs are not an option. It is simpler to use an SCR in this application. SCRs also seem to be rated for much higher loads at lower cost, even when two are required for every TRIAC.
I have read that a TRIAC is very similar, though not identical, to two SCRs in inverse parallel with the gates joined together. So I whipped a simulation up and I found that the circuit would always conduct in reverse and triggering the gate made it conduct forwards and backwards. Significant current (5 amps!) flowed through the gate terminal into the AC source or load. So I'm confused as how to control inverse-parallel SCRs.
Thanks,
Tom
