Engine RPM can not be directly correlated to HP output.
As has been mentioned before in this forum neither the
traction motors or the main alternator have built in fields
with permanent magnets.
Power output of a constant speed diesel-electric can be
controlled by adjusting the current level applied to the
field excitation of the main alternator.
Constant speed diesel-electrics have been experimented with
for freight locomotives but the fuel penalty is just a little
too high.
Constant speed diesel-electrics are, pretty much, only used
in passenger operations. The lighting, heating, and air
conditioning needs of just about all modern passenger equipment
are supplied by trainlined electrical cables connecting to the
locomotives. In the case of some locomotives there is a separate
diesel-electric power supply that handles this task. On some
others the equipment's power needs are supplied by another
alternator connected to the diesel used for propulsion.
Since the equipment's needs stay the same whether the train is
moving or not the constant speed diesel is necessary.
Think about standard rapid transit equipment. Every time there
is a gap in the third rail at a switch or something the lights
briefly go out. This is not a problem since the gaps are short
and the train is still moving and very shortly picks the power
back up again.
A loss of services at station stops or a reduction in available
power going downhill or drifting would not be acceptable in
passenger service.
Russ
----- Original Message -----
From: wollffee
To: BRHSlist@yahoogroups.com
Sent: Friday, 07 November, 2003 09:22
Subject: [BRHSlist] How does an F40PH work?
I found the operators manual for this loco and it states that the
engine runs at 893 RPM at ALL times during normal ops. Yet, it still
has the normal 8 power setting positions. If the motor always runs
at full speed, how is power to the wheels adjusted?
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