At a guess, 1300 hp is a maximum: even the GE U34CH of 1970 was able to take a variable amount of power for HEP depending on the train's demand. It would make sense to have HEP equipment capable of producing more HEP power than you expect to use in normal service: life is full of surprises.
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As for how much is needed... Somewhere in the back of my memory I seem to have a recollection that HEP for passenger trains is on the order of 75hp/100hp per car. Remember that it's not just lighting: modern passenger cars have electric heating. Electric heating (as I have noticed at electric-bull time!) really eats up the old kilowatts. And these locomotives are going to be pulling and heating trains in ALASKA!
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As for how much is needed... Somewhere in the back of my memory I seem to have a recollection that HEP for passenger trains is on the order of 75hp/100hp per car. Remember that it's not just lighting: modern passenger cars have electric heating. Electric heating (as I have noticed at electric-bull time!) really eats up the old kilowatts. And these locomotives are going to be pulling and heating trains in ALASKA!