Our process plant makes use of large 400 VAC 3 phase UPS system which then supplies, DCS, instrument DBs for field devices, DCS servers and finally 400 VAC MCCs.

This is the first plant where I have come across such system, and we have had a few very bad plant outages because of UPS failure.

I would like to hear of any person who has similar installations wrt problems, solutions, general opinion of UPS?

<b>Moderator's Note:</b> wrt is text speak for "with respect to." Had to look that one up.

 

There are many causes may lead to UPS failures.
what alarms appeared before the trip?
how many channels you have "as redundancy"?
how is the batteries condition?

 

Agree with this last post, what alarms presented prior to the failure? Also, what is the configuration: two feeds or one? the KVA (or KWh) rating? the load under normal conditions? Are you doing maintenance on the UPS? The ones I've worked with required periodic inspection, air filter changes, battery checking, etc.