<The Ultimate Fight?: The Singularity v. Resource Depletion and the Limits to Growth The Oil Drum Countdown to $200 oil: $140 oil and speculation>
<DrumBeat: June 29, 2008 DrumBeat DrumBeat: July 1, 2008>

283 comments on DrumBeat: June 30, 2008

Comments can no longer be added to this story.

Show without comments | PDF version

AlanfromBigEasy on June 30, 2008 - 9:38am Permalink | Subthread | Parent | Comments top

The 31 billion Swiss franc TransAlp and related projects should increase passenger modal share for rail (240 kph trains) but the Swiss are planning on an 80% modal share for rail freight vs. heavy trucking.

Much of the portion of the 31 billion that was borrowed (much was "pay as you go" with taxes) will be repaid with new tolls on trucks after two major new rail tunnels are opened.

One tunnel will provide a level, straight rail path from Zurich to Milan using 58 km, 20 km and 10 km tunnels (from memory) for up to 300 trains/day and trains up to 1.5 km long and at speeds to 240 kph (150 mph).

SBB uses 16.7 Hz electricity (1/3rd of 50 Hz so they can convert from grid if need be, but they prefer making their own power in their own hydroelectric plants).

Best Hopes for SBB,

Alan

Comments can no longer be added to this story.
GreenMan on June 30, 2008 - 10:07am Permalink | Subthread | Parent | Comments top

What's the advantage of using a different frequency?

Comments can no longer be added to this story.
AlanfromBigEasy on June 30, 2008 - 11:13am Permalink | Subthread | Parent | Comments top

It allows you to use motors with fewer poles (or get greater torque from a given AC motor) AFAIK. I would like to know more.

Also some long distance transmission advantages.

Amtrak's NorthEast Corridor operates at 25 Hz south of New York City to Washington DC. With modern electric locos, Hz is no longer an issue. They convert single phase AC from wire to DC and then 3 phase AC

Hopes that helps,

Alan

Comments can no longer be added to this story.
TJ on June 30, 2008 - 12:46pm Permalink | Subthread | Parent | Comments top

The speed of the AC motor is determined primarily by the frequency of the AC supply and the number of poles in the stator winding, according to the relation:

Ns = 120F / p

where

Ns = Synchronous speed, in revolutions per minute
F = AC power frequency
p = Number of poles per phase winding

(from Wikipedia)

The lower the frequency the lower the motor speed, and the higher the torque available. Also easier gearing and better power factor in both the motor and the transformers.

Also, in general (with lots of exceptions):

DC motors > AC motors in cost
Synchronous AC motors > Induction AC motors in cost
Cheapest motors in big sizes around are squirrel cage induction motors. Three phase types are self-starting and can act as generators, for regenerative braking.

AFAIK, most traction motors used to be series wound DC, but now tend to be wound-rotor induction. Wikipedia notes the TGV is a synchronous AC, though.

Comments can no longer be added to this story.
AlanfromBigEasy on June 30, 2008 - 7:05pm Permalink | Subthread | Parent | Comments top

Simple schematic diagram of a modern electric locomotive

http://www.railway-technical.com/elec-loco-bloc.shtml

FYI for those curious,

Alan

Comments can no longer be added to this story.
RBM on June 30, 2008 - 7:36pm Permalink | Subthread | Parent | Comments top

Neat !

BTW,
One time you mentioned a 40 pole motor was the most you knew of in locomotive applications.

I told one of my HVAC/R instructors about that (he's a retired nuke engineer) and he expressed an interest in seeing a schematic of that.

Have you come across such a thing ?

I poked around google a bit.

Comments can no longer be added to this story.
AlanfromBigEasy on June 30, 2008 - 8:19pm Permalink | Subthread | Parent | Comments top

I think it was hydroelectric. Matches optimum RPM for the turbine with the generator by increasing the # of poles.

2 pole 50 Hz = 3000 rpm

2 pole 60 Hz = 3600 rpm

40 pole 60 Hz = 180 rpm

40 pole 50 Hz = 150 rpm

www.andritz.com/hydro-media-media-center-hydro_news_2003_05_en_1_.pdf
1.3 Mb pdf

40 pole is not the limit of those in use, I think I once heard of a 62 rpm 116 pole hydroelectric generator. Not economic today (and rewinding it would be "problematic").

Alan

Comments can no longer be added to this story.

283 comments on DrumBeat: June 30, 2008

Comments can no longer be added to this story.

Show without comments | PDF version