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UPS Output Voltage going High

UPS Output Voltage going High

UPS Output Voltage going High

(OP)
This may not be the right forum but....

We have had two incidents lately of the output of UPS's going to overvoltage and burning out downstream power supplies. Does anyone have experience of this type of fault.

Units are Emerson Liebert 230V output 50HZ 6kVA and 4.5kVA  

RE: UPS Output Voltage going High

Is this two seperate UPSs causing the incidents?

Also, I think a model number would also help.  

RE: UPS Output Voltage going High

(OP)
Yes
GXT2U

RE: UPS Output Voltage going High

Call Liebert!

Plus there is not enough information to comment on? What were measured over voltages?

It could be cheap power supplies too!

RE: UPS Output Voltage going High

(OP)
We have called Liebert and have their reasons, I am not convinced and hence seeking any others who may have had same problem. Output was measured at 278 V.

RE: UPS Output Voltage going High

278V compared to what?

What are the reasons Liebert giving? If you dont share those here how can one tell if they may be right or wrong?

Knowing Liebert for years, I would still give them benefit of doubt unless you have some information to disprove them.

You have provided zero information so far  to make any technical assessment of any kind.

RE: UPS Output Voltage going High

(OP)
I did not ask anyone to comment on what liebert have found. I asked if anyone had experienced any overvoltage problems. I also noted that the output was 230V.

RE: UPS Output Voltage going High

So you want to hear what you want to hear! Not find the truth. I did not realize that.

RE: UPS Output Voltage going High

(OP)
I'm sorry rbulsara but if you are going to be abusive then I am really not interested in hearing from you.
I am interested in whether others have had a similar problem and what they have found so that I can look in other directions and explore other possiblities. I do not think that as a responsible engineer I should give 'the benefit of the doubt'  

RE: UPS Output Voltage going High

A few questions.

You mention that the output voltage was 278 volts. How was this measured? Was this measurement taken whilst your downstream equipment was damamged ar taken at a later time?

Was the UPS on-line at the time or was it in bypass (reserve) mode?

 

RE: UPS Output Voltage going High

(OP)
At a later date. After the downstream power supplies where damaged. The unit(s) showed no signs of any alarms or on bypass

RE: UPS Output Voltage going High

I've never heard of anything like this. Was the 278 volt output confirmed with more than one meter?

If there were no alarms, then something is wrong with the internal monitoring circuits and with the output regulation.

Alan
----
"It's always fun to do the impossible." - Walt Disney

RE: UPS Output Voltage going High

Another question.

Was the output voltage of the UPS checked with an oscilloscope to see whether the voltage was still sinusoidal?

As described it does sound very peculiar. I can only surmise that for things to stuff up this badly with the UPS that there is some severe software error.

RE: UPS Output Voltage going High

(OP)
The 278V was confirmed at site and off site in local emerson agents office. More to come when I get report....  

RE: UPS Output Voltage going High

It may well be that the output AC capacitors have gone faulty/ open circuit. I have seen this on an AEG system quite recently. This causes the modulated DC to pass to the output circuits without filtering and the peaks are seen as a high voltage.
The only thing that worries me is that the AEG system detected the high voltage and switched off the inverter. This does not seem to have happened in your case.

UPS engineer http://www.powerups.co.uk

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