Western Power Fridge magnet

[JohnW2]

During that period, you either corrected your post or else it corrected itself!

You were quick - I posted, saw that I'd b******d up the quoting, and edited it straight away.

Yes, I probably was fairly quick in starting to respond - but I had to leave my my almost-completed response (complete with the quote of your original 'imperfect' post) sitting in the 'reply window' until the power came back on before I could post it.

Talking of the power cut, it transpires that one of my routers was running off a UPS, but something about the 'power cut' (I suppose probably something immediately before the power went off) seems to have killed the UPS - such that nothing now comes out of any of its outputs, even when it is mains-powered. I need to investigate!

Kind Regards, John

 

[ban-all-sheds]

That's a pretty fundamental requirement for a UPS - not to fail when there's a power cut.

Are you sure it failed when the power went off, and not when it came back on?

 

[JohnW2]

That's a pretty fundamental requirement for a UPS - not to fail when there's a power cut.

Indeed it is!

Are you sure it failed when the power went off, and not when it came back on?

Up to a point. I was using a laptop which was wirelessly connected to the router in question, and I lost my internet connection immediately the power went off. That, in itself, could have been due any number of faults in the (quite old) UPS (dead battery, faulty inverter or sensing circuitry etc.). However, when power was restored, nothing was coming out of the UPS, even though it must have been (mains-derived) right up until the moment the power failed - so something additional must have 'happened' to the UPS, although I suppose that 'additional something' could have happened when power was restored.

It's all a bit odd, and I'll see if I can discover what has happened. I wonder if the power cut (all 3 phases) might have been in response to an automatically detected voltage problem which damaged the UPS just before the power was disconnected - do you think that's credible?

Kind Regards, John

 

[bernardgreen]

Here we go pedantic, UPS or SPS.

UPS Un-interruptable Power Supply

The invertor is running continuously and supplying load. It is fed by DC derived from the mains float charging the battery. If mains failure occurs the invertor continues running on the battery without any break or phase or voltage change in the supply to the load

If the invertor fails then the load is moved to the incoming mains. This can result in a jerky transfer with phase and/or voltage changes.

SPS Standby Power Supply,

The invertor doesn't run until mains fails so there is a break after mains fails and the invertor has started. The break is normally only one or two cycles ( at 50 Hz ) and would only affect "sensitive" equipment.

The big advantage of a UPS is that failure of the invertor will be discovered before any mains failure occurs.

 

[JohnW2]

UPS Un-interruptable Power Supply ... The invertor is running continuously and supplying load. It is fed by DC derived from the mains float charging the battery. If mains failure occurs the invertor continues running on the battery without any break or phase or voltage change in the supply to the load. If the invertor fails then the load is moved to the incoming mains. This can result in a jerky transfer with phase and/or voltage changes.
SPS Standby Power Supply, ... The invertor doesn't run until mains fails so there is a break after mains fails and the invertor has started. The break is normally only one or two cycles ( at 50 Hz ) and would only affect "sensitive" equipment.

Indeed - but I strongly suspect that the ones used 'domestically' are almost invariably the latter, yet they are equally invaliably called 'UPS's!

The big advantage of a UPS is that failure of the invertor will be discovered before any mains failure occurs.

Indeed - although in my case, something more complicated has seemingly happened. Although battery/inverter failure could explain why output disappeared immediately the power failed, it cannot, in itself, explain why output did not return when power did! Watch this space!

Kind Regards, John

 

[ban-all-sheds]

Don't rule out something as prosaic as a fuse blowing when a bunch of old batteries suddenly demanded to be fed when the power came back on.

 

[JohnW2]

Don't rule out something as prosaic as a fuse blowing when a bunch of old batteries suddenly demanded to be fed when the power came back on.

Indeed, that's why I need to investigate. There is no externally accessible fuse, but there's no telling what might be inside!

Kind Regards, John

 

[plugwash]

Here we go pedantic, UPS or SPS.

UPS Un-interruptable Power Supply

The invertor is running continuously and supplying load. It is fed by DC derived from the mains float charging the battery. If mains failure occurs the invertor continues running on the battery without any break or phase or voltage change in the supply to the load

If the invertor fails then the load is moved to the incoming mains. This can result in a jerky transfer with phase and/or voltage changes.

SPS Standby Power Supply,

The invertor doesn't run until mains fails so there is a break after mains fails and the invertor has started. The break is normally only one or two cycles ( at 50 Hz ) and would only affect "sensitive" equipment.

The big advantage of a UPS is that failure of the invertor will be discovered before any mains failure occurs.

Maybe different terminology from different fields

It appears that what you are calling a "UPS" is what UPS vendors call a "double conversion online UPS". What you call a "SPS" is what UPS vendors call an "offline UPS".

There are various devices desribed as "line interactive" or "delta conversion online" between the two exteremes.

 

[mfarrow]

I got my magnet today. Do you think it will stick to my meter?

 

[bernardgreen]

It appears that what you are calling a "UPS" is what UPS vendors call a "double conversion online UPS". What you call a "SPS" is what UPS vendors call an "offline UPS".

It seems that once again mis-use of a name has occurred,

In the 1980 a UPS provided un-interrupted power when the mains failed. For some equipment such as radio transmitters and receivers this un-interrupted power was essential. The hick up in power as an "offline UPS" powered up could corrupt the transmission or reception of a digital data package. The communications protocols would ( in 99% of events ) detect the error and request a repeat of the corrupted package but this could delay data on a busy communication link.

Obviously in the event that a UPS invertor failed there would be a hick up but mains failures, total or brown out were much more frequent than failed invertors in well designed and built UPS invertors.

 

[JohnW2]

In the 1980 a UPS provided un-interrupted power when the mains failed. For some equipment such as radio transmitters and receivers this un-interrupted power was essential.

Since such electronic equipment virtually invariably runs off DC, the combination of what you call an "SPS" and the PSU will (if adequately designed) nearly always achieve a truly "un-interrupted" (DC) supply to the equipment, since a capacitor (and associated regulation) in the PSU will maintain the (DC) supply to the equipment during the cycle or three of 'changeover' from mains to inverter supply.

Kind Regards, John

 

[bernardgreen]

what you call an "SPS" and the PSU will (if adequately designed) nearly always achieve a truly "un-interrupted" (DC) supply to the equipment,

For individual items of equipment that is often valid but when it is a rack of equipment with many items including cooling fans a no break AC supply was essential.

Some items of the equipment would have needed their power supply modules to be modified to have larger capacitors if they were to continue operating smoothly over a mains break of a few cycles.

Some "elderly" sites were powered from a motor generator set with a fly wheel to provide mechanical energy storage to power the site until the standby diesel generator was at speed.

 

[JohnW2]

what you call an "SPS" and the PSU will (if adequately designed) nearly always achieve a truly "un-interrupted" (DC) supply to the equipment,

For individual items of equipment that is often valid but when it is a rack of equipment with many items including cooling fans a no break AC supply was essential. ... Some items of the equipment would have needed their power supply modules to be modified to have larger capacitors if they were to continue operating smoothly over a mains break of a few cycles.

There is obviously a valid theoretical basis to everything you say, but I do wonder how significant these issues really are/were in practice. Certainly today, a cheap 'SPS' running a PC with a (very) cheap PSU seems to be able to achieve a 'seamless' transition from mains to inverter supply.

Some "elderly" sites were powered from a motor generator set with a fly wheel to provide mechanical energy storage to power the site until the standby diesel generator was at speed.

Indeed - I very nearly mentioned that. A flywheel is the mechanical engineer's 'capacitor'!

Kind Regards, John

 

[westie101]

The item in question

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[ban-all-sheds]

Covers Skeggy - that popular seaside resort in Western England