diesel generator power factor

The load determines the power factor. If you have a load such as electric heating, the PF = 1. If you have motors the PF might be 0.80.

Usually the generators do not need derating for 1000ft or so, after that as I remember 2-5% derating is recommended for every 1000ft.

Derating is also required for ambient above 40⁰C (cooling, air density, humidity, etc all matter). For 55⁰C it may go as low as 90% (ie DRF=0.9)

Unfortunately both these parameters are design specific and hence not only manufacturer but also model dependent. Since it all depends on how that air is utilised, how the heat is dissipated and the capacity of the machine to withstand heat.

The actual answer may be obtained from the manufacturer

for example

I thought your question was about power factor.

Please note that the alternator loading is in Amperes and the Diesel Engine loading is in HP. So, control alternator loading by monitoring the ammeter and control the engine loading by monitoring the kW meter.

It is very clear that the question is how to calculate engine + alternator de-rating at the said ambient conditions.

I have worked many years with generator design and calculations.

Engine derating is different from manufacturer to manufacturer, for the same power.

Derating can be different for each engine, even the same manufacturer's product . If the engine is turbocharged, derating is different, In the cases the charge air is Inter/aftercooled, derating also varies.

The only reliable way how to calculate derating for a certain engine is to refer the leaflets of the manufacturer's laboratory tests. Diagrams on the engine's own leaflet is indicating the power decrease in altitude and ambient temperature variations. Values are extracted from real test results.

The same logic is valid also for the alternators. Altitude is effective on the cooling air of the alternator (The cooling air is thin in the high altitudes, therefore cooling is poor), as well as the ambient temperature.

You must refer the manufacturer's test reports and must take both the engine and the alternator deratings into consideration for your own ambient conditions.

Kindest Regards