I think the explanation is that the diesel engines aren't used for motive
power, instead, they drive generators (alternators?) that in turn power
electric motors for motion, by way of motor drive circuitry.

That's the way I've heard it explained anyway.

Dunno about the air supply.

--
WB
..........


"Jon Elson" wrote in message
...
I was at the local ice cream place that is adjacent to one of the local
train tracks.
The Amtrak pulled up to exchange passengers at the nearby station. A bit
after it stopped, I heard a very familiar and unexpected sound.
It was a large air compressor driven by a 60 Hz 3-phase motor. I'd guess
from the sound it very well could be a Quincy, and I'd guess maybe 15-25
Hp 4-cyl 2-stage, with pneumatic unloaders.

Anyway, it struck me as just a tiny bit odd they'd use an electric
compressor, as they have mechanical power available off the Diesel engine.
I also noticed the Diesel didn't seem to change speed when the train
accelerated, so I'm guessing they run a single engine at 60-Hz synchronous
speed all the time, so they can distribute 60-Hz power for air
conditioning, etc. to the coaches. So, no aux engine for the non-traction
power.

Anybody know anything about this?

Jon