From: grr@cbmvax.commodore.com (George Robbins)
Newsgroups: rec.railroad
Subject: Re: Diesel vs. Electric Locomotive Maintenance
Date: 7 Oct 92 06:52:19 GMT
Reply-To: grr@cbmvax.commodore.com (George Robbins)
Organization: Commodore, West Chester, PA

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?

I addressed both cases.  I'm not sure that AC motors are universal for
locomotives, though they may be common in lower power applications like
multiple unit cars and transit equipment.

Note that AC motors in modern usage don't run off the distribution
frequency, rather the AC current is rectified and then turned into
variable voltage/frequeny poly-phase AC by solid state inverters
(choppers, switches, whatever).

> |> air brakes and perhaps a steam-heat boiler or provision for head-end
> |> power for the passenger service.
> 
> 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?

No argument here, just that my classic half of my example is based on a
PRR GG1, which had a steamheat boiler, a newer technology unit or one
intended for freight service can omit this.

> |> 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.

On possibility is that by US standards many of these European lines
may be high density.  The "high density" Northeast Corridor offers about
one through train per hour each way during daytime and evening - more
commuter trains in specific urban areas of course. Traffic density on
many "mainline" freight lines isn't all that high either.

There is also a point where if you have most of the mainlines electrified,
it makes sense to almost everything except for local switching, none of
the US railroads achived this point.  The Pennsylvania probably came
closest, but was never able to justify electrification of the western
half of their system.  The eastern electrification also relied in part
on depression era government assistance.

I don't know whether there are significant fuel vs. electicity cost
differences in Europe, fuel in the US has traditionally been cheaper
than anywhere outside of OPEC.  There are probably other factors like
the ecomomics of "owning" the extra fixed plant of the electrification
overhead, but the real problem seems to be that diesels work quite
nicely, are affordable, flexible and are the accepted "standard
practice".

Please note that there are a number of traditional "railway managment"
references/texts that address the economics of steam/electric/disel
traction.  Using these as a framework and pluggin in contemporary
numbers still gives valid results.  Check any good technical library.