3000VA UPS Makes Vibrating Noise When Running On Battery

[Anonymous user]

I have a 3000VA UPS that makes a loud vibrating noise when it operates on the internal batteries. The UPS is fully functional but it sounds like a freight train.

Any idea why it is doing this and how can I fix?

[BillP]

If you are NOT an electrical engineer who is comfortable working with high voltage and high currents, then I would strongly suggest that you obtain professional help because there is a risk of bodily harm or death with the following.

I have been it this situation before and it can be an easy problem to fix, a royal pain to fix or a potential death sentence for the UPS. I have never seen the guts of a 3000VA unit, but this might help you.

Put the UPS in a “brain dead” mode, this will discharge many of the capacitors. Look up “brain dead” if the information is needed. DO NOT reconnect the batteries or the utility line at this time.

WAIT about 10 minutes and then remove the top cover of the UPS. The wait time will allow other capacitors with “bleed resistors” more time to discharge.

Are any of the retaining bolts that secure the transformer(s) loose? Put some Loctite or clear nail polish on them and retighten. Your job may or may not be finished.

Inspect all of the electrolytic capacitors and see if any of them are bulging or leaking. You will need to replace all capacitors that are bad. BERFOE you replace them you MUST test them with a volt meter to see if they are discharged. If you are not sure, short the leads with a 10K, 1 watt resister; don’t use a screw driver. Use the same value caps but you can go slightly higher in voltage but be realistic. FYI: I prefer Japanese capacitors.

Find a Variac, turn it on, and adjust the output voltage to match the utility line. The Variac will isolate you from the utility line. You will have to make an AC adapter cable for your 3000VA unit so it will mate with the Variac. The Variac is there FOR YOUR PROTECION!!!

Reconnect the internal UPS batteries. Plug the UPS into the Variac. Turn the UPS on and let it boot. Connect a load to the UPS and turn the load on. A 500watt load should cause the problem to appear.

Turn off the Variac and see if the freight train is less noisy. DO NOT perform this test by unplugging the UPS or Variac from the utility line.

Is the UPS still making noise like a freight train? PUT ONE HAND in your back pocket and place the BACK of your other hand on the metal part of the transformer(s). Can you feel the transformer vibrating? If yes then you have a lamination problem.

You can also place a “C” clamp on the transformer to see if the vibration lessens. This will help to verify the problem BUT it is not a solution. A transformer with bad laminations get very hot and can catch fire. You must address this problem!

I have read about some solutions to correct lamination problems but I have never tried them. I think these solutions would also be too risky at your power level. You can canalize a busted 3000VA and steal the transformer(s). You might find a used transformer on the Internet. You might be able to have the transformer re-wound and they would redo the plate laminations but this is an expensive option.

Do not pitch your UPS. Keep this UPS for parts or find someone who will take it off your hands for parts.

I do not mean to sound like your father with some of my remarks but I do not know your abilities and I have witnessed too many accidents. I hope you understand.

[Anonymous user]

WOW, I was expecting a simple two sentence answer to my question.

I had to read your post several times to grasp what you are saying and suggesting. You seem to know what you are talking about and I do appreciate the safety concerns.

I do not own a variac. I had to look it up on the Internet to see what is does. Do I really need one? Also, my UPS has a standard plug on it. I changed it back when I bought it.

When I calibrate the UPS, I attach a 30% load and just unplug the UPS from the wall until the battery dies. Am I doing something wrong here?

I will remove the cover over the weekend and look around to see if anything pops out as being a problem.

[BillP]

It might be worth to check this topic as well, if your model reads SU3000NET (or SU3000INET)

http://forums.apc.com/spaces/5/smart-ups-symmetra-lx-rm/forums/general/13075/su3000net-rattles-on-ba...

[Anonymous user]

I had something like that with a different model.

It was the fan, that had come loose.

When on battery the fan is on / on high speed...

[Anonymous user]

You were right, I got a nice shock from one of the capacitors!

Two caps are bulging.

I am more of a PC guy. I asked a friend who is a serious electronics guy and he is willing to replace these for me.

Thank You

[Anonymous user]

Thank you for this link. It was very interesting to read.

A friend is willing to do this surgery for me. I will share this link with him because there may be other problems that should be addressed while the body is on the table:)

[Anonymous user]

Thank you for the suggestion.

I was hoping it was the fan at first but the vibration was too strong.

[BillP]

I need to modify something that I stated.

Not all Variacs provide line isolation. My Variac does but you pay more for this option. I do a lot of repair work on older tube electronics and line isolation is a must-have for me. A Variac also allows me to vary the line voltage so I can test the high and low transfer points of a Smart UPS.

Your APC is a sophisticated AC generator of the inverter type. When you “pull the plug” to do a manual calibration, the UPS loses its ground reference. But there is more.

Search the Internet for articles on “Ground to Neutral Bonding”. If you run your UPS unplugged from the wall, then you lose the “ground to neutral bonding” and this is a serious safety issue. Play It Safe!

Good luck on the repairs, Thomas!

[BillP · Accepted solution]

Great Link, Wolf!