# UPS fault



## Black Dog (Oct 16, 2011)

cuba_pete said:


> I have an APC Symmetra 500kVA (480V) unit which recently failed outright in two successive incidents. The first time it was under about 180kW load. From the logs it appears that it first saw a ground fault on the third phase of the output. Screen shots indicate about 2500A. For some odd reason this fault was passed through to the 800A input breaker which tripped. The short duration was set to 300 msec. The fault was. Less than 5 ms at the output of the UPS, and of similar duration at the input. No independent monitoring outside of the UPS is present, so those values cannot be corroborated.
> 
> Within 5 seconds the UPS had errors on two of the modules, output waveform errors, and then tripped all (7) battery breakers...end of show.
> 
> ...


Bump!:thumbsup:


----------



## guest (Feb 21, 2009)

I don't feel that the fault "passed through" to the inputs....in the direct meaning of the statement anyways. 

What I feel happened in rapid order was:


Ground fault happens on output;
UPS switched to on battery mode to try to keep power up;
Phase fault blew out the inverter module for that phase;
UPS switched back to utility due to module failure; and
Main breaker tripped due to the fault still being present.
Remember that in the world of electrons, this can all take place in milliseconds or seconds. 



The tech deleting the files is odd, I think he was trying to hide something. 



That said, APC's quality (on the smaller units anyway) has gone waaayyy down, the reliability they founded the company on is long gone ever since a certain company bought them out.


----------



## cuba_pete (Dec 8, 2011)

*More info*



mxslick said:


> UPS switched to on battery mode to try to keep power up;
> Phase fault blew out the inverter module for that phase;
> UPS switched back to utility due to module failure; and
> Main breaker tripped due to the fault still being present.


I will reply as needed since there are many considerations.

the UPS never actually made it to battery mode. No parts were damaged according to APC (yet). The UPS is up and running, now, with all modules (14 in total).

The fault still being present is likely, but under-reported by the UPS' internals.


----------

