From: chalup@presto.ig.com (Michael Chalup)
Newsgroups: rec.railroad
Subject: Re: Diesel vs. Electric Locomotive Maintenance
Keywords: electric diesel traction
Date: 13 Oct 92 03:48:20 GMT
Organization: IntelliGenetics, Inc., Mountain View, California USA

In article <1992Oct6.164839.19878@ntmtv> adrian@ntmtv.UUCP (Adrian Brandt) writes:
>In article <35601@cbmvax.commodore.com>, grr@cbmvax.commodore.com (George Robbins) writes:
>|> An electric (we'll deal with a powerful AC one) has to in effect
>|> have a power sub-station to step down the 11-50KV power from the
>|> overhead to a lower voltage ~300-600 Volts that can be used in brush
>|> type DC traction motor or handed economically by solid-state rectifiers
>|> and switching circuits.
>
>Don't modern electric locos have AC traction motors?
>

They normally use series-type DC motors, the DC supplied by a
rectifier on the locomotive.  These type of motors have the advantage
of high starting torque and simple speed regulation through either
resistive grids or chopper control.  The upcoming exception are plans
for 3-phase synchronous motors, avoiding the brush/commutator problems
(speed control is achieved by a variable frequency supply on the
engine).  I don't believe any units of this design are currently
operating in the U.S., other than the new LRV's in Baltimore.

BTW, The last AC motor locomotives used on the NEC were in the GG1's,
now retired.  The E60, AEM7, E44, E33 are all rectifier-equipped.


>

>Almost nobody uses steam heat anymore.  Isn't head-end power is so much
>nicer with an electric because you don't need to have a smoke-spewing
>noisy diesel engine revving the whole time?
>

Yup, got to keep the prime mover in the F40PH running pretty fast to
supply all the 'Hotel Power' for the consist!  But in the great scheme
of things this is rather unimportant.  I'll gladly take a bit of
exhaust than depend on the steam heat and failing car generators
and batteries of the pre-HEP era.

>
>|> For just about anything except the Northeast Corridor and commuter
>|> rail, the diesels have displaced electric traction, even where the
>|> fixed plant is paid for and there is an effective fleet of locomotives.
>
>Why do you suppose western Europe is so extensively electrified?  With
>each passing year more and more of the relatively few remaining diesel
>lines are being electrified.  Another thing I've noticed is that here
>in the USA I frequently hear talk of how electrification is only worth-
>while on super-high density traffic lines.  While in western Europe,
>I've seen many electrified lines that had relatively low traffic levels
>(like a train every half hour to an hour or so).  It seems that just
>about any line that carries passenger traffic (freight-only lines are
>few) over there is either electrified or scheduled to be electrified.
>

Except in a few (but growing) number of cases, the U.S. rail system is
owned by for-profit concerns.  Whatever the RR chooses needs to be
ultimately profitable to its corporate balance.  Electrification has
alway involved very high fixed costs.  Except for exceptional
circumstances (ventilation problems in tunnels, steep mountain grades,
large traffic densities with limited R of W, substantial commuter
loads) major mainline electrification has not been typically performed.
Even where it was installed, the economies of long run-throughs with
the same power that were made available by dieselization often
resulted in its abandonment.


By U.S. mainline standards, a train every half hour to an hour would
be be very high traffic levels.  If this is mainly passenger service,
it would probably only be matched in the US by commuter operations or
maybe some segments of the NEC.

Europe, however, has nationalized railway systems.  Goverments have a
much better time executing large capitol improvements like
electrification than private concerns; profitability is not of primary
concern.  Also the absolute distances involved in many cases is less
than the major trunk lines in the U.S.  Europe has a vastly higher
passenger traffic density than the U.S. (with the possible exception of the
NEC).  The high level of this traffic does make electrication more
economically and politically desirable; freight is probably of
secondary concern.  As you point out, its the passenger lines that are
getting the 'juice'.
 
I think mainline electrification does have a brighter future in the
U.S., but I seriously doubt that a single inch of catenary will be
erected for any non-govermental, non-subsidized service.  Even with
wire up, the advantages of run-throughs and power pooling will
probably stop any RR from seriously considering electric freight
operations.

I highly recommend William Middleton's book 'When Steam Railroad
Electrified' for a more detailed discusion on this topic.

>
>-- 
>
>Adrian Brandt (415) 940-2379
>UUCP: ...!ames!ntmtv!adrian
>ARPA: ntmtv!adrian@ames.arc.nasa.gov


				My two cents,
				Mike Chalup

				Part-time motorman
				Part-time wrench turner
				Part-time conductor
				Part-time track worker
				Western Railway Museum

Newsgroups: rec.railroad