UPS on Diesel Generating Set

What is the loading on the system?

Thanks TonyS,

The UPS are ment to supply the office workstations(computers, printers and scanners). The esitmated demand load for all these workstation is about 80kVA. The 120kVA UPS had been procured and delivered to site by the client.

Please kindly advice if there are technical disadvantages in this system.

what percentage of load does the UPS present share with the generating set?

Is that what you mean?

No, the UPS just won't supply more than the combined output of the remaining battery power plus 100kVA. The load the UPS presents to the DG dependS upon the conversion efficiency of UPS at the load it is supplying.

Thanks. I appreciate

Disadvantage? Usually it's an ADVANTAGE to have a UPS in conjunction with a DG. The DG needs time to come on line, critical systems, such as computers in mid--process, cannot tolerate more than a small fraction of a second of no power. So the UPS ensures a continuous flow of energy to the critical equipment, but only for as long as the batteries last. The DG is then making sure the batteries are kept charged.

As long as the fuel holds out of course...

Another important factor in selecting the DG rating for supplying the UPS is the harmonics that the UPS presents to the DG.

This requires that the generator is oversized and the AVR is appropriately selected to suit the harmonic ridden voltage feedback signal it receives from the generator output terminals.

DG vendors have articles on the subject (for example - Cummins website).

Thanks Raghun. I appreciate your comments.

Kindly send me a link for more details.