Shutting Off 120VAC Before Zero Cross

[ElectronKing]

Greetings:
I have an application where I'd like to turn OFF a small inductive load (vibrating motor, 120vac, ~0.5A) immediately (within a few microseconds) after conditions are met within my microcontroller application, thus I can not use a TRIAC which would switch off but I'd have to wait for zero crossing.

I was wondering if anyone has any suggestions on how to do this.  Perhaps using a GTO???  I also realize I'll also need some type of snubber circuit since I'm often turning off before zero cross but not sure how all this would look.  Really out of my wheelhouse here (I'm a microcontroller/firmware guy).

Thanks.

[Kleinstein]

The alternative would be an bridge rectifier and than an MOSFET or IGBT between the + and - therminals of the rectifier.
It is also possible to use a series pair of MOSFETs with source connected together.
In Theory also Photomos could work, though the load could be a little high for the common types.

Yes you need beefy snubbers. Depending on the switches this could be RCD or similar. Simple RC snubbers will not work well.

[ajb]

A back-to-back MOSFET switch would be the typical alternative to a TRIAC.  Two MOSFETS, connect the gates and sources together, one drain is the input and the other is the output.  Note that your gate drive will be referenced to the source terminal, which is riding the AC voltage.  How you manage that depends on your application, and what other connections to the outside world you require.

Won't the mechanical inertia of a 60W motor swamp your microsecond timing, though?

[Cyberdragon]

If you use IGBTs or IGCTs you won't need any snubber. IGCTs are still latching though, so you'd have to pulse the gate off.

[wasyoungonce]

....Won't the mechanical inertia of a 60W motor swamp your microsecond timing, though?

He could plug brake the motor

[ElectronKing]

Thx for the replies.  Still trying to wrap my head around this.

Ajb, good point about the mechanical inertia.  I've been trying to quantify that for about a week now to see where limit is.

As for IGCTs... did a quick search but couldn't find any that would meet my spec.  Any idea where I would get something like this for 120v, 0.5A?

As for back to back MOSFET switch approach, looking to drive gate with output of micro-controller.  Not sure how to reference microcontroller side (DC) with MOSFETs.