Mobile vs Stationary Generator 2

[CuriousElectron]

Hi,
Are there any derating factors that need to be taken into account when sizing a mobile diesel generator as opposed to stationary? One modelling software gives a substantially higher kW rating if mobile unit is selected for the same modeled load.
I wonder if that's is because this vendor doesn't carry a certain rating and so it just provided the next higher size unit.

Thanks,
EE

 

[waross]

Mobile is probably standby rated.
If the stationary unit is rated for prime power, 10% overload is allowed for a couple of hours out of 24 Hours.
In many cases a 100 KVA prime power set will be rated at 110 KVA standby power even though both are the same set.
In the larger sizes, the prime power set may have the same engine but extra accessories;
eg: A much larger oil sump, an oil cooler, or other additions to support 24/7 running.
Serious sets of any size will be rated in KVA at 0.8PF, rather than kW.
The voltage used is important.
The same set will have different KVA and kW at 240 Volts compared to 208 Volts.
Three phase to single phase conversions can mess with ratings.
I have been caught about everyway possible on undersized sets.
Always when the customer got a better price sourcing the generator himself.
One set with the KVArated at 240 Volts instead of 208 Volts. Too small for the load.
Another set, KVA rated at three phase rather than single phase. Too small for the load.
Someone guessed at the load and the set was much too small. I changed out 6 or 8 of these for appropriate sized sets.

Bill
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"Why not the best?"
Jimmy Carter