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Military MEP and Aircraft Gen-Sets

Engine Size for 35 kw Generator End


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  #11  
Old 12-01-2017, 04:38:21 PM
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Default Re: engine size for 35 kw generator end

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Originally Posted by Vanman View Post
While a popularly repeated rule of thumb is 2 hp in per kw out, this assumes a ghastly generator efficiency, but does result in plenty of extra hp for brief periods of overload, but also results in plenty of extra fuel consumption due to the oversized engine.

Probably fine for small sets that are more likely to see intermittent overload and have somewhat less efficient generators.

Lacking the specified generator efficiency, I find 1-1/2 hp per kW to be a vastly more realistic guess. So to get 35 kw, you'll be needing right around 53 hp, give or take, to drive the generator.

The generator will be somewhat less efficient at less than full load, and at relatively light load it could be as poor as 2 hp per kW.

It'll work just fine, but a 170 hp engine driving 20 or 30 hp load will be very inefficient, unless the engine speed can be lowered approximately in proportion. But the generator must (presumably) run at 1800 rpm. Unless it has a gear drive on it, as most PTO generators do. If the input to that is 1000 rpm, it might just work dandy.

A 170 hp 453 sounds like turbocharged and running at least 2500 rpm. I would think that it might be more like 100 hp at the 1800 rpm required for your generator if it doesn't have the PTO gear drive input. In that case, still way too big IMHO.

But, if this is all stuff you already have, and the usage will be infrequent, it may still make sense for you.
And it will want to "wet stack" like a garden sprinkler making a mess of it's surroundings.
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Old 12-01-2017, 04:43:51 PM
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Default Re: engine size for 35 kw generator end

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And it will want to "wet stack" like a garden sprinkler making a mess of it's surroundings.
Well, yes, there is that.
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Old 12-01-2017, 06:18:24 PM
Thaumaturge Thaumaturge is offline
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Default Re: engine size for 35 kw generator end

I use a rough calculation of 80% efficiency for gen horsepower. Based on that, the 50hp diesel would be a good fit. All the moreso being rated at 1800 rpm same as generator head. By my calculations: 50 x 0.8 = 40 x 746(watts) = 29840. So not full potential, but, as has been stated, good overhead without stressing gen head.
Your mileage may vary....
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