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| Subject - UPS's that don't like generators | |
| unknowingsap |
I wonder if any of you guys had run into this problem? I found out today that a small office building in our facility had lost power this weekend for an hour or so. The backup generator came on and supplied the loads for this building (like it was suppose to) and everything seemed fine. Although after a short while the computers started failing. Then people began noticing that all of the individual UPS's supplying the PC's were beeping constantly and clicking from normal power to battery power. Sorry I don't have much more info than that. I will start tomorrow to figure out what the problem was. But if someone has run into this before it could sure save me some time. Thanks in advance for any help. |
| iwire | Two possibilities I can think of right off the bat. 1)The generator is turning to slow or fast which is what controls the 60 Hz. To low or high and the UPS may take over. 2)The generators voltage output is to low or high again the UPS might take over. RPM directly controls the Hz RPM will effect voltage too but the voltage should be adjusted with the voltage regulator. In other words get the cycles dead on 60 Hz with load then once that is established adjust the output voltage with the potentiometer on the voltage regulator. |
| JimmyDee | Did a job for General Telephone (Now Verizon) where we hooked up a huge emergency generator to operate all the computer equipment and on the test run, took out a bunch of computer equipment. The final diagnosis was that the windings of the generator were not big enough to eliminate all the transients that the electronic equipment made and it took out a ton of power supplies for electronic equipment. I wonder if the transients produced would some how shut the UPS equipment down. If I'm not mistaken, the UPS should just shut down when the voltage gets low but the frequency hitting it, may control the shut down. I wonder if it is frequency controlled, if that could be adjusted. Jim |
| iwire | It very much depends on the UPS type, the small UPS on my home PC can not control frequency or the voltage. It only takes over when voltage is low, once transfered it makes a square wave AC that is OK. The bigger and better commercial types of UPS do control the voltage and frequency. But if the incoming voltage or frequency is to far out of whack the UPS will cut off the incoming line and run off the batts. On these units all incoming AC power is converted to DC and put into the batteries. All output power is then drawn off the batteries and converted back to AC @ dead on 60 Hz. I also believe it makes the standard sine wave AC. This is all the time not just when there is a power failure like the home UPS I have heard before about problems with certain size generators not being compatible with certain size UPS systems. From what I have read is you get a bouncing or surging of current that makes the generator speed unsteady which makes the current more unstable which makes the RPM even more unstable and around we go until something fails. Solutions I have heard of are load banks, smaller generator, larger generator. We have installed load banks (think giant electric fan cooled toasters) before to steady out the power from a grossly over sized generator for a computer room. It is also bad for a large diesel engine to run at speed without a large enough load to get up to full operating temp., you get raw diesel into the exhaust system. The load banks solved both problems although it is not fuel efficient. |
| unknowingsap | Thanks to you both. On Monday I had a look. The small UPS is made by a company called APC. The frequency and voltage were both good. The UPS had a sensitivity adjustment on the back of it. I moved it from high to medium and that took care of the problem. I don't have an osciliscope (sp?) so I don't know what the sine wave looked like, sorry. Hope this may help others, good day. |
| Ship Shock | quote: Hey; We have this problem on ship all the time. Electronics gear is not tolerant of diesel gensets. IMO, the isochronous governors on diesels respond too quickly to changes in the load, causing a "hiccup" in the frequency. It's especially noticeable if you're only running on one generator...the entire grid hz is captive to the one governor. As you parallel up a few more gennies, the problem becomes less acute. There's nothing like a turbine for a nice smooth powerband. Cheers; |
| Ship Shock | And speak of the devil... Kinda strange to reply to a two-month old problem, but just today we were de-trashing some of the holds and came across the Mother of all AC line conditioners, which is destined for jettisonning. All 300-400 pounds of it. Back in the early and mid 80's, when this ship was put into service, they had to install this beast upstream of their data systems circuit(s). Looking with trepidation at this critter, it occurred to me that in a jam like Brother Unknowing was in, with a whole building full of fussy little digital gew-gaws being fed from one dinky little genset, a fellow could sell and install one of these puppies for his customers. They get "clean" AC during a blackout,without adjusting every little cotton-pickin' UPS and digital clock in the joint, and their clever electrical savior makes some nice extra profit/commission out of the gig. "Turning slowly in the FAST direction" Cheers; |
| geekboy | Its the feq. on the generater, I installed two 100amp gens. (natural gas and propain) and I had to stick a herz monitor on the generaters and adjust the hertz screw that was located on the top of the moter. The voltage and hertz screws are marked in the manual and tell you what hertz level it should be pumping out. |