How common is it (or was it) for PC power supplies to have circuit breakers built into them? (for excessive current draw, short circuit protection, etc)

I know some are fused for the same or similar purposes and plenty of bad ones out there don't have good enough protection to keep from frying the system when they fail, but has anyone else come across ones that have breakers in them instead (either manually reset ones or automatically resetting ones)?

I have a 200 watt EMACS power supply that probably was originally intended for server or external drive usage (or maybe just for AT or XT clone systems without remote power switches) as it has a rocker switch on it and no AC mains power switch leads/button/switch.

It's come in really handy for bench testing various AT-compatible boards, but it's also ended up saving me from some nasty mistakes that otherwise might have damaged or killed hardware or at least damaged the PSU. (like installing un-keyed chips in the wrong orientation, and while I've generally avoided it, I suspect protection against mixing up the 2 AT power connectors would be a big one for this sort of protection)

It also immediately shut off from 12V fan wires that had managed to come loose and short-circuit, but that's rather obvious behavior.

OTOH I have lost a couple DIP DRAM chips that got inserted backwards (or had a bent pin I'd missed) so there's still some margin for certain types of damage.

My unit simply resets itself when the power is disconnected (rocker switch turned off or power cable removed) and I believe it functions via a solenoid or other electromagnet type device. (I haven't opened it up)

It also seems to have a thermocouple reculated fan that shuts off at low temperatures. (somewhere around 65F or 18C going by the conditions it didn't power on when I had it running this winter)

My PSU is an EMACS model ET2-4200UF