Power factor of diesel generator for a purely resistive load bank 2

[chao_david]

I'm confused with the factory test report of my 15 kVA, 60 Hz, 220 V, single phase diesel generator. This was tested using a purely resistive load bank where in the power factor is 1. The load bank used can provide maximum load of 15 kW. Since the generator has a rated 0.8 power factor, the 100% load is 12 kW.

Why is it that at 25% to 75% load, the power factor is less than 1?

Thanks!

 

[genhead]

The load bank will have a cooling fan driven by a motor running at around 0.8 lagging power factor. As the resistive load increases so the total power factor increases towards 1.0. At lower loads the inductive fan load is relatively more significant.

 

[chao_david]

Follow up question. If my load bank fan connects to an external power source, does that make the power factor unity? I'm thinking that the coils from the generator somehow contributes to the inductive power factor?

 

[waross]

That test report may be suspect.
There may be some inductive load.
Rock steady frequency from no load to full load is uncommon on a set that small.
Rock steady voltage from no load to full load is uncommon on a set that small.
The KVAR varies;
1.47 KVAR at 25% load.
1.76 KVAR at 50% load.
1.24 KVAR at 75% load.
There may have been a 3 HP motor connected. That would make the numbers believable but still suspect.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

Rock steady frequency from no load to full load is uncommon on a set that small.

Quite true; uncommon, but certainly not impossible, especially if the governor is a good- to excellent-quality isochronous one...but that being said, I'm leery of the test report, too; I'd rather see some time traces of frequency recovery with step load changes, as the frequency reported may only be that found once the system re-stabilizes.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

With the standard 3% droop a frequency of 60.6 Hz would reflect a 33.3% load.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

Correct, if running in droop mode and not isochronously, if these selections are even available in this governor, something not provided in the OP. [ I know, I know, that's something like the Pogo comic line: "If we had some ham, we could have ham and eggs, if we had some eggs." ]

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[shallywawa]

The prime mover was tested at full load and 10% over load. The generator was only tested at part load.
Most customers balk at the price when they see the adder for reactive load banks.

I have a 6k yuchai generator, lasts about 4 hours on a 20lb tank, but since propane is for

ever I plan on getting a large tank installed and feeding my dryer, generator and stove

from the one tank.

I'm happy with mine. how ever it's important to remember that power from propane will cost

you double the cost of power from diesel fuel as propane has a lot less "energy" when

compared to diesel.