MEC407 wrote:That's not really unusual. The GEVO-12 in its current incarnation produces over 4500 horsepower, but GE rates the ES44AC and ES44DC as having 4400 horsepower for traction. EMD locos are probably similar.
I suspect 4,500 gross HP for the GEVO V12 prime mover installed in a locomotive is significantly understated!
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Consider the following published energy conversion efficiencies. (These incidentally represent "best case" efficiencies for top of the line components):
- Main alternator – 96%
- Traction motors – 93% (this is for an AC traction motor; DC traction motors might be a % or two LOWER).
- Electrical power controls (rectifiers, inverters, etc) - 95%
Combining the above gives an overall engine-to-drawbar transmission efficiency of ~85% (= .96 x .93 x .95)
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What's this mean? It says for 4,400 HP to show up at the drawbar, 5,187 HP (= 4,400 / 85%) must be supplied to the main alternator by the diesel engine.
Next consider a locomotive's “parasitic losses”, ie. the power required to run the locomotive auxiliaries. Items like radiator cooling fans, intercooler blower, traction motor blowers, the air brake compressor, aux alternator (ie. the control/lighting/battery charging generator), etc. all consume power. Combined these easily represent another 100 HP, probably much more.
Finally there's the power required simply to move the locomotive itself - 180 or so tons of locomotive deadweight has gotta be kept rolling before the drawbar can apply any horsewpower to pull a train. Depending upon the speed there's another 100 - 200 HP is "lost" to that activity.
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Bottom line: For 4,400 HP to show up at the drawbar and be available for pulling a trailing load, well in excess of 5,000 HP must be developed by the locomotive's prime mover.