Ed_Flecko

We have a Cummins powered generator that powers my data center in the event of power loss.

We recently had a power outage and were planning on using the generator until our local utility provider completed their repairs and restored power. Our facilities manager suggested we do NOT run on the generator because it was discovered the power output was very "dirty" and it may damage our UPS devices, Network Servers, etc. In short, it might damage some/all of my data center equipment!

Can someone tell me what causes a generator power output to be "dirty", and how would one correct that? The generator OBVIOUSLY does us no good if it's power output is that poor!

I'm sure it's also difficult to be accurate, but does anyone have a "best guess" of what it takes and co$t$ to correct this situation.

Thank you!
Ed

CraigV

Contact the generator manufacturer and discuss the issue with them, and get a definitive answer regarding the type of equipment the generator is able to power.

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wildleg

If your UPS for the data center doesn't provide some kind of power conditioning, you got rooked. If you don't have a UPS for your data center, then someone screwed up. find out the specs for your UPS and find out what can be done to make it better, if it is not providing power that is conditioned to suit the center.

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brian john

Depending on the size of the generator and the size of the UPS.
If you generator is a real generator for commercial applications typipcally 30 kva and larger and the UPS load is less than 50-60% of the generator size in kva. Then you facility manger shoud get his resume in order to look for a job.

ASSUMING he does not know somnething your are not aware of.

Power as supplied by commercial generator is when properly set up and properly sized is as good or better than the utility power.

We service and test generators.

With the site load connected one utilizes a line disturbance analyzer to capture possible transients, harmonics while viewing the voltage waveform.

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Brian John
Leesburg, VA

Mshea

Just to reinforce what others have said. A properly sized generator creates pure power without any distortion. The UPS is normally only there to provide transition from normal power to UPS until the generator is up to speed and voltage is stabilized (20 to 30 seconds) and then transfer from UPS to the generator.

The computer loads are in fact the largest source of harmonic distortion (dirt) on the system. IE the output of the generator with no load is far cleaner than the output after the computers are connected. It is the computer power supplies and the fluorescent lights that distort the output of the generator.

Your IT manager does not seem to understand the source of the dirt is the IT system and the generator won't make it worse. In fact it is likely, as stated that the power output of the generator is cleaner than the power from the utility. IE the neighbours of the data center might be making a mess of the power too and by running on a generator their dirt does not come onto your lines.

This is not even a huge issue. Even though your neighbours are the source of Dirt on the utility the power company does work to correct these distortions.

I have to add a caveate. Many of the problems of harmonic distortion caused by switching power supplies and electronic ballast have been mitigated by better design of those power supplies. IE they cause less of it and are better resistant to it too.

brian john

But with a generator that is sized to small harmonics can be an issue.

Lastly moderen PC power supplies are not that sensitive to dirty power.

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Brian John
Leesburg, VA