Hi all, we have a 5000VA UPS from APC, 5 years old (incl.batteries) which still holds for various minutes at full load so we are keeping it. Downstream from that one we have about 8 servers which load the UPS at about 80%.
The UPS is connected to a 16A line (220V) with a C charachteristic curve. Normally the whole thing draws about 10.5A from there.
When we have a blackout and then the electricity comes back, the 16A breaker trips, then after a few minutes the UPS batteries are flat and the whole thing goes down.
I have tried pulling up the breaker when the batteries were totally flat, and it would stay up for about 3.5 seconds (this is approximate because I didn't really measure that with a stop-watch), then broke again. I waited 10 seconds then I pulled it up again and that time it stayed up. Reports from my colleagues are similar.
Now looking at the C charachteristics curve for the breakers, (it is the one at the bottom of page 2, isn't it:
Do you have a reasonable explanation for what is happening here? It seems there is like a very large capacity loading... Might this be a thing like "memory effect" of the old batteries which we have in the UPS?
Unfortunately our panelmount voltmeter measures a moving average so is not reactive enough to let us see how many amperes we are drawing in those 3.5 seconds.
Thank you