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DC2FR > INFO 08.07.02 21:55l 70 Lines 3850 Bytes #999 (0) @ WW
BID : 872DB0GV02B
Read: DB0FHN GUEST
Subj: RE: Traction (KB2VXA)
Path: DB0FHN<DB0ZWI<DB0CHZ<DB0ERF<DB0ROF<DB0CWS<DB0FP<DB0GV
Sent: 020708/1944z @:DB0GV.#HES.DEU.EU [Frank4t/Mtl OP:DF5FF] DB19c1 $:872DB0GV
From: DC2FR @ DB0GV.#HES.DEU.EU (Wolfgang)
To: INFO @ WW
Hello Warren and all other rail fans,
thank you for your reply - it was interesting for me you explained the
different current systems of the US railroad. Some years ago, I visited
New York and made a boat trip around Manhattan with the "Circle Line".
I saw the electrificated railroad lines, also visited the Penn Station -
but didn`t know which system of electricity is used by Amtrak or NJT.
Warren wrote:
> Here in the Northeast, we had two (that I know of) systems, the
> Pennsylvania RR, a major portion called The Northeast Corridor from
> Boston to Washington used 11KV 25~ and the Reading which served
> Southeastern Pennsylvania used 25KV DC.
Are you sure that it's really DC? At 25 KV? I wonder - this would be the
highest DC voltage ever used for railroad traction all over the world.
What sort of traction motors / current system inside the locos they use ?
Because DC cannot be transformed and DC commutator motors must be operated
at voltages not exceeding about 1500 volts, I was a little confused about
this. I have heard, a couple of years ago the Russians tested a 6 KV DC
system, as the highest voltage DC system designed for railroads.
But as far as I know, the system did suffer from many problems and failures
of high-voltage operated DC commutator motors, so as I know it was given up
and substituted by the modern 25 kv 50 Hz AC system.
The New York city subway supplies the current by a 3rd rail in side of
the track - I think 600 - 800 v DC or so? Similar systems are used here
in Germany, too.
Berlin, Hamburg, Munich and Nuremberg also use a 3rd rail side supply
(750 vdc), while other cities like Frankfurt and Cologne prefer the over-
head cable / pantograph supply, also with 600 - 750 vdc.
The latest tramway / subway cars now also use three phase asynchronous
motors for traction. They are feeded from the DC supply by means of
transistorized (IGBT) 3phase inverters.
The 16 2/3 Hz railroad locos had since their introduction in the 1910/20`s
mostly the same principle: a transformer for stepping down the high line
voltage (15 kv) to only some hundred volts (max.) supplying the commutator
motors. Speed / traction power control was done by varying the motor
voltage with a lot of taps in the transformer windings.
An example: the DB-locos type 110/140 (introduced in the late 50`s and well
known and used until today) have 4 traction motors, one for each axle,
rated for 920 kw at 487 volts and 2075 amps. Transformer has 28 steps
from 26 v ... 487 v maximum. Total power 3700 kw or 5000 HP.
Now, modern locos in three phase technology, like the 101/120 types or the
superfast ICE trains, also have transformers, but no stepping anymore.
A secondary rectifier generates a constant intermedium DC voltage of 2800 v.
With this, three-phase inverters are feeded to supply the four asynchronous
traction motors with variable 3phase AC system 0 to 2200v rms, 0 to 120 Hz.
Because asynchronous motors are significantly lighter than commutator dc/ac
machines, higher power per motor can be installed. So, up to 6000 kw and more
now can be realized by 4-axled locos (1500 kw per motor) - in conventional
16 2/3 Hz commutator technology at least 6 traction motors have been needed
for this (so f.e. in the famous fast train loco "103", released in 1965 as
the fastest and most powerful loco of the German railways DB).
Less maintenance costs due to no commutator and brushes, more reliability,
the possibility of feeding back braking energy to the mains, and - last not
least - the option of easily constructing multi-system locomotives are other
significant advantages of the three phase traction technology. So, more and
more older 16 2/3 Hz locos are substituted by the modern 3phase types.
73 de Wolfgang, DC2FR @ DB0GV, Frankfurt - Germany
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