We have Hyundai 7250 watt portable generator that we use in power outage situations. The generator is feed into a UPS system. When we use the generator it fluctuates from 57 Hz to 60 Hz. The load is constant at about 5500 watts. My questions is, should a generator rated at 60 Hz change or should it always stay at 60 Hz. We have people in to monitor the frequency and they have verified it goes up and down from 57 to 60.

Thanks,

 

Bouncin,

There's something wrong with the governor of the portable generator. It should be able to maintain 5500 Watts at 60 Hz with no problem. The only caveat I could think of would be the power conversion assembly of the UPS may not look like a "stable" load depending on how it "fires" or "gates" the silicon controlled rectifiers.

You may consider asking the UPS manufacturer if a portable generator can be used to power the UPS, or if they have some recommendations for smoothing the load seen by the portable generator.

Some portable generators are really only meant to power lights, refrigerators, microwave ovens, alcoholic drink mixing machines (blenders), and electric saws and drills. Some are "inverter" type machines meant to drive electronics like TVs and satellite dishes and computers. Maybe the type of generator you have (the non-inverter portable generators are much less expensive than the inverter type portable generators) isn't the right type for the UPS.

Hope this helps!

 

Please confirm from UPS drawing that, its isolating transformer at incoming supply has an zigzag winding to ensure what Mr CSA has asked for.

Generator frequency fluctuation is a governor issue if load is not varying with very high d(MW)/dt, you need to fine control the liquid fuel valve.

Ask the diesel engine manufacturer to do the same.