building an H-bridge

================================== An H-bridge usually is used to get fwd and reverse direction with pwm speed control on a brushed dc motor. A triac is usually used to switch on the AC line to a load like a lamp part way through the half cycle. Perhaps you have a new idea to combine these two normally entirely different applications in a unique and unobvious way? Tell us more.

I can imagine using four SCRs in an H-bridge fed from a full-wave rectifier to drive a permanent-magnet motor in either direction. You could also use two triacs and a center-tapped transformer.

used to build an H-bridge?

Probably not that unique and unobvious... just wondering if 4 identical triacs can be used instead of 2 npn and 2 pnp transistors.

Thanks

Michael

AC or DC?

Once switched on, triacs stay on until the current falls below the holding current, so in a DC application they would not switch off unless the current is interrupted.

Triacs are normally used in AC applications where the current drops to zero twice in every cycle.

Maybe you could use one of these?

used to build an H-bridge?

be used to build an H-bridge?

Ok, thanks. Guess that's the deal killer right away, then. I wasn't aware of this fundamental feature of triacs.

Just to clarify: when you say "once they've been triggered ON that's how they want to stay until the current through them goes close to zero", you don't mean the current through the gate, do you? (You mean the current through A2 and A1, right?)

Michael

GTO's ?