Need input requirement for APC UPS system for generator provided power

[Anonymous user]

We had power shut down on July ,4, 2008, and we rented a 15kw generator to provide power to our server room, we have total six APC UPS, 2x 3000, 3x2200, one 7500RT, The electrician connect power cable to panel, measured 120V on phase 1, but all UPS refuse to use power provided by generator, stays on Battery mode, We have to force emergancy shut down ( not a fun stuff!)
We have the power shut down every year since two years ago. Last year, we rented also a 15kw single phase two hot wires generator last year, and had no problem at all. the only different this generator seems smaller and older( after I have find out , this generator we got is made on year of 2002, last year we had generator made on 2005)
I did some reasearch on what kind of power the UPS will accept, but I miss some of the numbers, this is what I have found
• Slew Rate <1Hz/Sec
• Ramp-in Time < 10Sec
• Freq Tolerance <+-5%
_• High/Low/No RMS Voltage-------------Need*_
*• THD(Total Harmonic Distortion)-------Need*
*• Dv/dt(Change in Voltage over Time)---Need*

Cab some one help me to have this number?

Thank you very much

Jerry Tan
July 7, 2008

[BillP]

Hi Jerry

First, before trying a completely new generator, you may want to adjust the UPSs sensitivity. On the standard SmartUPS 3000 and 2200 units, there should be a button on the rear of the unit, near the outlets, labeled Sensitivity. There will be a green LED next to this button, which can be pressed with a ball point pen or paper clip.

Bright LED = High Sensitivity, most likely to use battery when on generator power
Dim LED = Medium Sensitivity, less likely to use battery when on generator power
LED OFF = Low Sensitivity, very unlikely to use battery when on generator power

These settings can be changed on the fly and then you can test at a later date.

Since you were able to run on-line off a 15kW genset earlier, it's very likely something that can be addressed by adjusting UPS sensitivity.

[Anonymous user]

Thank you very much for your reply, JoeMomma

This is why I need to find out the input requirement of UPS, There was no problem last year, even without adjust the sensivity, but this year, its a older generator, and looks like have dirty power output, we even lower the sensivity, still won't accept by the UPS, So what I need to find its requirement from UPS input ,and make sure the generator we are going to rent next year meet the requirement, Plus, we are going to rent a bigger (most likely will be 22.5kw) and newer generator.
If you or anybody can provide the numbers I am missing that would be very apprecieted.

Thank you,

Jerry

[TheNotoriousKMP_apc]

Matt,

While I don't want to steal your thunder on this, a lightbulb went off while reading this thread.

Jerry,

You stated you have a 15kW generator powering these 6 UPS? If my math hasn't failed me, that would be a total consumption of 20.1kVA, which, even at a .9 Power Factor, you're at 18kW, and at a .8, you're at 16.08. How was this generator even sized to work on this entire load?

The other thing is that you stated this 15kW generator was a single hot. The RT7500 requires a 2PH+G, so that probably doesn't help (and makes sense why that UPS ran online last time).

I don't think that obtaining the numbers for THD for the UPS's are going to help any. The generator should be sized for at least 2-3 times the total load powered (even if the load is just 6 UPS's). That would mean a minimal 40kW generator, to eliminate any excess harmonic distortion on the output of the generator and should allow the UPS's more than sufficient power to run online.

My guess is that if you were to take a single 2.2kVA UPS, and run ONLY that on a gen-test, that it will work fine. You can probably even add one more UPS to the mix and that will run online fine with the generator output.

[Anonymous user]

Kevin,
Thank you for your number. That really help us later on.

We have 20 servers and couple of switches routers in the server room, one 2200 UPS take care of switches/routers, load on 20%, when we have power shut down, we can shut down about 14 servers, only let 6 servers up and running, two of them are blade servers with SAN connect to RT7500, what we did last year, when these 6 servers up and running, the actually reading on A is only 15A, so we even later turn on one of our AC to cool dwon the server room. So the capacity is not an issue.

To explain why the single phase generator can provide power to two phase RT7500, need to start from two years ago. (Before I work for this company),On 2006 power shutdown,a three phase generator connected to the panel, because of most of the load are on phase 1 and 2, ( only one UPS connect to phase 3), the generator tried so hard to balance the power between three phases, and really struggled, the generator have to shut down.
Last year, I rent a single phase generator with two hot wire, one N and one G, 180 degree apart on the two hto wire, so when I connected two hot wire to phase 1 and 2, instead of 208V, its 240V between phase 1 and 2, which the RT7500 can handle fine, I simply move one UPS from phase 3 to phase 2, so all UPS and devices are up and running.

I have talked to United Rental , the different between this year and last years 15kw generators is this year generator is made on 2002, last years was made on 2005. the model is IPS 15kwC-T,
We are going to rent a bigger generator for next year, they have Magnum MMG25 and MMG35, What I need from APC is the input requirement for UPS,
• Slew Rate <1Hz/Sec
• Ramp-in Time < 10Sec
• Freq Tolerance <+-5%
• High/Low/No RMS Voltage-------------To Be found
• THD(Total Harmonic Distortion)-------To Be found
• Dv/dt(Change in Voltage over Time)---To Be found

I need last three numbers,
I am very appreciated if you can give me any information of these.

Thank you,

Jerry Tan

[Anonymous user · Accepted solution]

prcdiscover wrote:
We had power shut down on July ,4, 2008, and we rented a 15kw generator to provide power to our server room, we have total six APC UPS, 2x 3000, 3x2200, one 7500RT, The electrician connect power cable to panel, measured 120V on phase 1, but all UPS refuse to use power provided by generator, stays on Battery mode, We have to force emergancy shut down ( not a fun stuff!)
We have the power shut down every year since two years ago. Last year, we rented also a 15kw single phase two hot wires generator last year, and had no problem at all. the only different this generator seems smaller and older( after I have find out , this generator we got is made on year of 2002, last year we had generator made on 2005)
I did some reasearch on what kind of power the UPS will accept, but I miss some of the numbers, this is what I have found
• Slew Rate <1Hz/Sec
• Ramp-in Time < 10Sec
• Freq Tolerance <+-5%
_• High/Low/No RMS Voltage-------------Need*_
*• THD(Total Harmonic Distortion)-------Need*
*• Dv/dt(Change in Voltage over Time)---Need*

Cab some one help me to have this number?

Thank you very much

Jerry Tan
July 7, 2008

The transfer points are adjustable. Try searching the knowledge base or reading the manual. Keep in mind that the power quality from generator varies significantly depending on load. If you're using standard IT equipment with no power factor correction, it is very high in crest factor and rich in 3rd harmonic and the generator will need to be significantly oversized ( 2-3 times the kVA load of the connected load) to accommodate harmonics.