UPS MALFUNCTION

[vmac100]

Gents,
i have two International Power Machines' BlancedPower Plus, BP+225, 225kVA UPS machines that are presently malfunctioning.
We obseved that when the units are started, the start process is okay, showing 'UPS NORMAL' on the indicator. However, when we connect load to the units, they shutdown with the following messages 'transferred to bypass' and 'retransfer inhibited'.
Has anyone had any experience with these make of UPS that had similar problems that were resolved?please i need advice.
also, on assuming duty as the supervisor of the team, i found out that the data sheets were not available,can i get advice on where i can obtain such?
Thanking you for your co-operation and do have a great day.

 

[rbulsara]

My first inclination is that you have excessive inrush current causing the UPS to go to bypass. Are there many transformers connceted as load to these UPSs?

 

[candu6]

Is this a new inverter or have you been using it for years? Has the loading changed? Have you done any maintenance?

 

[vmac100]

Thanks guys.
there is this fear that there may be laser printers, photocopiers, etc connected as load to the UPS output. I plan on carrying out a load rationalization within the next few days. Also, the UPSes are not new, and have been in use for some years.First line maintenance has been conducted, the history of which i am still trying to get hold of.
Rbulsara,i think you may have a very valid point there.while discussing with the team members, they informed me that before the UPS is started up, the output breaker to the load is closed to the busbar and the UPS input breaker to the busbar is closed. Then the UPS is started up.this does not seem like standard practice, but i was informed that the UPS holds if this procedure is followed.
Do you have any views on these?and any more suggestions?

 

[rbulsara]

vmac:

It is a standard and recommended procedure to 'start' a UPS in Bypass mode first and apply "all loads". Then transfer it to 'online' position via soft transfer (closed transition). This way the UPS electronics will not see inrush. I suspect that what your team members told you, please veify that.

But the UPS is tripping just because you turn on a copiers or so you may want to look more closely elsewhere. Look for a new piece of equipment recently added. I do not think a copier or printer will affect a 225kVA unit.

Please explain what you meant by "when we conncet load to the units...". All the loads at a time? individual loads?

 

[vmac100]

Rbulsara,
thanks again for your effort. Each UPS unit feeds four office buildings, and these loads are added together at the same time by closing the output circuit breaker.that's what i meant by 'when we connect load to the units'.
what you suggested that a copier or printer should not affect a 225kva unit is what i and my boss have been debating.we quite agree with you.what about 10 copiers and 30 printers?
i will do as you suggested and conduct load inspection in the buildings.
i am still open to suggestions.
warm regards

 

[rbulsara]

At the least follow the procedure I mentioned. Let us know what happens. Is UPS manufacturer's fied service involved in this?

I still think, even with 10-30 printers/copiers if they are not all turning on and off at the same time it should not be a problem.

If this issue started only after the maintenance, I suspect something else is wrong.

 

[vmac100]

Hi Rbulsara and my other good friends, I am really grateful for all the help you have rendered so far with regards to my malfunctioning UPS. However, I will have to crave your indulgence and ask for more assistance from you.
Yesterday, I followed the advice given by Rbulsara and had the load online on the BYPASS CB before bringing the UPS on. It was able to take either of the loads on the two ways connected to the busbar. The load measured on the two ways A and B are as follows:
WAY A: R=11A; Y=10A; B=12A
WAY B: R=38A; Y=49A; B=43A
However, when I loaded both ways at thesame time the unit was able to carry them without shutting down automatically but there was a high and rising hummimg sound from the UPS unit, the sound was rising so fast, and was very abnormal compared to when either of both ways were loaded, that I had to order that the unit be shutdown. Mind you, this is a 225kVA machine, capable of delivering about 220A/phase based on the existing settings.
My question is, what can be the problem?which component of the unit may be defective?etc?
I may interest you to know that a diesel generator is also connected to the same busbar to feed the UPS load, while the UPS is down and the earth current measured on the cable from that generator, which connected to the same busbar earth as the UPS was about 20A. Can this be an issue with regards to the UPS high noise level?
Also, the Specific Gravity of about 50% of the batteries on the battery bank is about 1.15. Though the battery link voltage was about 410V (as required from the battery bank), can this also be an issue?
Please, I need help on this and desperately so. Any ideas and suggestions will be highly welcomed.
Thanks for your help and continued support.
Regards

 

[rbulsara]

normal battery Specific gravity is either 2.15 or 2.25.

1.15 is too low!!!!! Yes this could be a contributing factor. At least one that needs to be corrected regardless of the problem you have before you place this UPS online.

So fix the batteries first. You need to contact the service department of the UPS mfr or thier authorized representatives. Do not rely on slightly cheaper 3rd party maintenance cos.

 

[rbulsara]

Also is this UPS always fed by a generator? Or is it noramally fed by utility?

Try it on utiltiy only first. Before that fix the batteries.

Also check the grounding. If it has 4 wire input (with N) in the bypass circuit and then connect the UPS output N only to the N of the bypass circuit and do not ground it.
Although the grounding is not the reason for your apparent problem but it should be code compliant and technically correct.

 

[alehman]

1.15 would be low for most types of batteries. Typical flooded cell specific gravities are 1.215 or 1.250 (fully charged). Some (not typical) batteries are as low as 1.15. You need to verify the specified gravity for your batteries, but it sounds like they are run down (and likely damaged if they've been this way for a while). Gravities should be fairly uniform.

The buzzing sound indicates to me that you definately have a malfunction - may be a bad transistor in the inverter or shorted output transformer. You may have a grounding problem as well, but I doubt that is causing your buzzing noise. I would have a reputable service organization take a look.

Obviously the generator is disconnected somehow when not in service? How does that work?

 

[e5fornow]

I think you have a battery problem, the noise you might be hearing might be from the UPS rectifers trying to charge the dead batteries. I would be consired about the 20A of ground current. Is this with the generator supplying the load or all the time? If you have a 3 pole ATS, make sure the generator's neutral is NOT bonded to the ground. Multiple ground bonds can cause excessive neutral-ground current.

 

[rbulsara]

I missspecified batt SG..alehman's values are more correct..but you do need to fix batteries

 

[gezcooke]

vmac100,

When a load is initially applied to a UPS the inverter uses the DC bus to supply the output. What you are describing is typical of a UPS that has a 'soft' DC bus - the sudden drag on the bus causes the bus voltage to dip below the inverter shut-off point sending the output across to bypass.

In most machines automatic restart is disabled as low DC shutoff would usually occur after a battery discharge and once the load is removed the DC bus recovers and you would end up with the inverter restarting and then shutting down again, etc, etc.

Given the levels of load I would suggest that the batteries are either completely u/s (as previously suggested above) or that that aren't even connected!! Check that the voltage level is higher with the unit running than with it off. Even so the DC capacitor bank should hold up with the light load you are looking at. As for the sound these things sound bad even when they are working correctly!

I have played with IPM UPSs - but the last time was around 1989 and since then have been taken over by Exide, who were taken over by Powerware, who were taken over by Invensys, who were taken over by Eaton - so you are dealing with a UPS that is more than just a few years old.

In summary if you load is really so light change the UPS for a smaller one - the reduction in running costs will justify it!

Good luck.

 

[vmac100]

Thanks Gents, I am really very grateful for your input.
Yesterday, and in continuation with my troubleshooting activities, I carried out an offline load test on the unit using a resistive load bank. The unit passed with flying colours, with loads/phase getting as high as 171A without the unit shutting down or buzzing unbearably. I am so delighted.
What I have decided to do is to go on a load rationalization campaign in the affected buildings to ascertain the type of loads connected to the UPS points in the offices.
Further, I plan on changing out the electrolyte in all the batteries in order to ensure that they are within the range of 1.215 and 1.250.
Please if you have any other suggestions with regards to this issue, do let me know.
I am really very grateful to you all. You are GREAT!!!!!

 

[alehman]

You need to get a reputable battery service company to look at the batteries. Changing electrolyte won't fix bad cells. You need to find out why the specific gravities are so low.

Check the overall battery string voltage while connected to the UPS and with it in normal operating mode. If it is correct (roughly 2.25 volts per cell), check the voltages of the cells with low gravity. If they are the same as the others, there's a good chance they're bad. If they are substantially different, you may need to equalize. If the overall voltage is wrong, adjust it.

A battery service company can do all this for you in addition to some other tests. It's important to follow the manufacturer's recommendations and IEEE 450.

Also take a look at

http://www.cdtechno.com/cd/library/manual/f6741/RS1476.htm

 

[vmac100]

Good day guys, i do hope we are all hail and hearty here. i am not and you know why: an IPM, Balanced power plus 225kVA 3-phase static UPS machine that has refused to stop making an annoying and rising humming sound when switched on and loaded, forcing me to shut it down for fear of damage to it and any explosion that may injure my personnel.
After our last communications, i took the learnings and went on to recondition the batteries by changing the electrolyte in the ones that have the low specific gravity.
After that action, I put the battery bank on charge and was able to attain a battery link voltage of 410Vdc.
Next, i brought on a 3-phase resistive load bank and tested that machine. The machine was able to take 171Amps/phase, without that annoying buzzing/humming sound. Rather, the sound was level and the machine seemed happy and even eager to take more load.
Going forward, I deployed my crew to conduct a load rationalization campaign in the office buildings so as to remove all non-UPS friendly loads(?) like heavy duty plotters, photocopiers, etc.
After the load rationalization campaign was about 70% completed, because some office occupants were not available to allow us into their offices, I decided to test the UPS machine with weekend load which was not too high. Below are the readings I got:
LEGEND FOR LOAD ZONES

1 = Block G
2 = Block ATOP FLOOR
3 = Block BGROUND FLOOR
4 = Block BTOP FLOOR
5 = Block C
6 = Block AGROUND FLOOR + AX BUILDINGS

LEGEND FOR LOAD ON UPS
A= Load of 1
B= Loads of 1+2
C= Loads of 1+2+3
D= Loads of 1+2+3+4
E= Loads of 1+2+3+4+5
F= Loads of 1+2+3+4+6
G= Loads of 1+5
H= Load of 5
PARAMETER LOAD ZONES
A B C D E F G H
Ia(A) 9.7 9.7 21 27 56 23 42 22
Ib(A) 5.7 5.7 17 24 34 27 15 5.7
Ic(A) 7.9 15 29 39 49 33 20 9.7
kW 3 5.9 11 15 24 15 14 8.3
kVA 6 6.9 14 19 32 19 18 9.1
pf 0.64 0.53 0.8 0.76 0.77 0.73 0.76 0.8
Bat.Amps 3.5 3.5 6 5.4 7.6 4.8 ? 6.
MaxOutCF 3.58 3.48 3.08 2.76 3.1 3.80 ? 3.18
Noiselevel OK OK OK OK High OK OK OK
(PLEASE FOR EACH PARAMETER, THERE ARE EIGHT COLUMNS. SPACE CONSTRAINT HAS CAUSED A SPILL OVER TO THE NEXT ROW)

When the noise level got high and was rising, I had to shut-down the machine. Again, I wish to state that the machine did not shut-down and the CHECK SUMMARY which was displayed when we started the machine was GOOD.
Can you please look through this data for me and let me know if you have any ideas for me as to what the cause of the high and rising humming/buzzing sound could be?
All help will be highly appreciated.
Regards

 

[rbulsara]

What is rated DC link voltage? Ask mfr or refer to the manuals. How many cells of batteries are required?

Other suspect is the input filter on the UPS, at light loads (less than 20%)the input power may get over capacitive and possibly causing a resonance condition which could make this annoying noise/vibration. I have seen a similar conditon with a mismatched reactor for a VFD drive. (was not directly involved in that, but replacing the reactor fixed it).

If this UPS has input filter, disconncet it and see what happens. You got to involve the manufacturer (factory engineers) in this.