AC source fast short circuit protection device

[semir-t]

Greeting everyone,

I am looking for a fast short circuit protection device for AC sources that I could use when I am powering my custom PCB boards for the first time. I am not keen on using a fuse and would like to use something faster.

I found one device here but I can't seem to buy it: https://mediadesigns.co.in/product/medis-fast-trip/

Here is the video presentation of their device and this is what I am looking for:

I am hoping that someone knows some similar device that can be purchased.

[alm]

Chroma and HP/Agilent/Keysight make AC sources that can do this and a lot more. They are big and very expensive new, but you can occasionally find a deal used.

[David Hess]

DC short circuit protection can be used for AC by placing it within a bridge rectifier.

A benchtop variable AC power supply should be suitable.  A cheap way to do it would be to get a pair of power transformers sized for your load, and connect them back-to-back; this will just limit the current however.

[TheSteve]

This is worth watching:

[David Hess]

This is worth watching:

That brings up the question of how fast he wants it to be.  100s of nanoseconds is possible.  Relays are quite a bit slower.

[ifonlyeverything]

This is worth watching:

That brings up the question of how fast he wants it to be.  100s of nanoseconds is possible.  Relays are quite a bit slower.

I'm also interested in a similar project. My thought was for MOSFETs upstream of a relay. If the MOSFETs blow up and fail shorted, the relay will save the day.

[David Hess]

I'm also interested in a similar project. My thought was for MOSFETs upstream of a relay. If the MOSFETs blow up and fail shorted, the relay will save the day.

I would use a fuse instead of a relay as the fail-safe.

I think I would use a pair of back-to-back power MOSFETs to switch AC directly with a photovoltaic optocoupler to supply the turn-on bias.  For a fast turn-off, I would include a separate optocoupler to drive an SCR (probably a pair of bipolar transistors making an SCR) to short out the gate drive.  Now the control circuit is completely galvanically isolated from the power switch, so it can be placed anywhere convenient to measure the current.

Big TO-247 power MOSFETs are not too expensive and I think would survive shorting out a 15 or 20 amp standard 120 volt AC circuit until a fuse blew or breaker tripped.