UPS - Uninterruptible power supply - not the courier!

[Paul M]

1 hour ago, Jonk said:

 

Just out of interest, who's UPSs do you have?

The answer might explain why you have issues!

I'd have to look and I'm (happily!) not back in until Sunday. We have a number of the same units across the site, I think they are all the same.  We are a big energy user and have our own 132kv substation so our mains is usually good. The UPS units are battery backed and for control systems only. For critical heavy current equipment we have a couple of big diesel generators. They don't need to kick in too fast just so long as we can make stuff safe if needed down the line. There is some stuff that will just crash even if we keep the PLC's alive, big centrifuges for example.

Where units have gone into fault and also failed to by-pass we've had the manufacturers in to investigate. Not sure of the outcome of the investigations or whether a solution was found. I seem to remember a component failure was to blame.

[discardedastro]

I've got a bunch of Eaton 9130 units here which are full double-conversion units and have configurable bypass thresholds - basically if the incoming mains is within a voltage +frequency range it'll bypass in all internal fault conditions, but if there's an ongoing brownout or other mains fault it will hang on till it's out of internal power and then cut the power fully rather than let half-arsed AC in.

This is generally hugely preferable - it's not pretty when some AC-DC supplies set up for 230-240V suddenly get 100 or 50. The Eaton units are powering a bunch of computers (desktops, servers, disk arrays) and telecoms infrastructure (switches, routers, WiFi APs, etc). None of that tends to like weird voltages.

At $dayjob I've got an estate of a few hundred telecoms sites which are all -48VDC consumers - those just have rectifiers which are immensely tolerant of incoming AC being all over the shop and will do their best to produce some DC for recharging or powering of kit, but even those will give up in the end! To protect against rectifier faults, there's lots of rectifier modules, each rated for a couple of kW or so, so losing one doesn't mean the end of the world.

The trick with all of this is having enough monitoring in place that you get notified when something goes badly wrong, so manual intervention can happen (for work, that means dispatching someone with a generator - at home, much the same!)

For 12V stuff, double-conversion or just having a 12V charger attached to a bunch of 12V batteries (double-conversion by another name) is perfectly sensible and very reliable. It's when you need 230V for something where the components and electronics get fiddly - inverters are much more fickle and prone to faults.