As an electronics professional in my working days, I am always intersted in circuits. I was looking at a photo of Washington Union Station tracks with catenary all over the place. I realize the power all comes from one source. But in general in a setting like that, are all the wires essentially wired together, one big criss-cross grid? Or does each track have its own branch circuit? I am sure there are breakers cordoning it off into sections. So for example on a two track main, would the two stripes of wire be on separate breakers? Or would it be just one for the pair. Any other considerations I haven’t thought of?
Guess any electrified RR can shut off power to one track while running trains on the other tracks? To allow work on the catenary, if nothing else?
I think one of the frequent posters has some hands-on experience with this matter, but I believe there is a NEC ex-PRR power control room, probably within the 30th Street, Philadelphia complex, or at Zoo or N. Phila., with essentially a wire-and-track map of the entire system from New Rochelle to Harrisburg and the current end of wire in the tunnel south of Union Station. Insulation breaks are shown, each section has its own push-to-cut-power button (and possibly push a second time to restore) and some lights to give a report on conditions. Metro-North-Connecticut-DOT has its own, and probably Amtrak New Haven - Boston is another. Before my move to Israel, Sunnyside - New Rochelle was controlled in the same room as Woodlawn - New Haven, but I am pretty certain that is now controlled in the same room as Sunnyside -Harrisburg and Washington.
Individual tracks in each station can be switched on and off, and ditto each track in each section in multi-track RoW.
But I expect to be corrected in one detail matter or another. Like my false memory of New Haven 6-10 sleepers. Rode them over a hundred times too. But they were not 6-10s.
I should also point out that the power room has control circuits, not the actual power. Power is fed from the substations spaced along the line with on-off relays controlled from the power room.
Any one know the various steps to verify the power is off and stays off ? The old PRR equipment certainly would make one very cautious that power is off and stays off. Wonder if any equipment will be replaced ?
The NEC is single phase, but the power supply is presumably 3 phase. I am guessing that the 3 phases are distributed to different tracks to try to even out power usage.
Nope. PRR power supply is actually single phase. Note power lines are in pairs. Power is just like what comes into your home. Feeders to ground are 180 degrees out of phase so voltage feeder to feeder is twice that of feeder to ground.
Safe harbor generators provide this unique high voltage power. If comercial 3 phase power is used at power stations then. Phase balancing is actually done with motor generators called rotary converters in PRR dictionary. Or done electronically at the new Siemens power station being built in NJ. Also there are some phase balancing transformers.
Does mean that the rotary converters convert 60 Hz 3 phase directly to 25 Hz single phase?
Actually, I believe they might just do that. Either by how they are wired, or via gear reduction…
The “rotary converters” are more accurately named frequency changers sets, being composed of a 300rpm 24 pole 60 Hz synchronous motor coupled directly to a 10 pole single phase synchronous generator. There is a frame shifting arrangement on the set to allow for adjusting the power flow through the 25Hz lines as oppposed to the 60Hz lines.
Lots of woodworkers use rotary converters to create three phase power at their home work shops that are fed by single phase power.
Very interesting article. Can now understand why PRR, Reading, and New Haven RRs all started with 25 Hz 11 kV CAT. Statement by author that he did not know of any operating rotary converters is puzzling. He may have been only referring to 25 hZ to DC converters. We Know Amtrak still uses 60 hZ to 25 hZ converters.
Also the use of Ignition rectifiers and later Ignitron rectifers that led to their later use on RR locos.
These were traditionally called phase converters, essentially being a free running three phase synchronous or induction motor with the single phase input connected across one winding and the three phase output connected across all three windings. Some means is needed to get the rotor turning as with any single phase induction or synchronous motor.
The N&W electrics, the VGN Squareheads and the PRR Big Liz all used phase converters.
The term “rotary converter” traditionally referred to machines that combined a stationary field synchronous motor armature with a shunt wound DC generator. The armature windings would be connected to AC fed slip rings on one end and a DC fed commutator on the other end. Most of the power transfer between AC and Dc was through the windings as opposed to torque generated by the armature.
Rotary converters could also be used to convert DC to AC, with small units being used in the DC districts of major cities to provide AC power.
As I wrote before, the frequency changer set in Safe Harbor was/is a motor generator set. This is very different from the traditional meaning of “rotary converter”.
- Erik
I find myself impatient for Rick Rowlands to finish up with his red Glyptal and get this running for at least one Youtube video, replete with zarks and other mad-scientist effects:
https://www.flickr.com/photos/33523379@N03/15178605648/in/album-72157647667854548
Quoting Erikem: “These were traditionally called phase converters, essentially being a free running three phase synchronous or induction motor with the single phase input connected across one winding and the three phase output connected across all three windings. Some means is needed to get the rotor turning as with any single phase induction or synchronous motor.”
When I was working and issuing replacements to the line maintenance people, I was amazed that the techs could not look a the motor on a vacuum pump and tell if it were a single phase or three phase motors, for each of the single phase motors had one or more capacitors on it to give the motor a jump start. At firt, we kept all pumps of a certain size under one part number, but we made life easier on the techs by giving pumps with a single phase motor one p/n and pumps with a three phase motor a diffierent p/n.
As an electrical engineer who was used to three phase power, I found this article of interest:
https://en.wikipedia.org/wiki/Amtrak's_25_Hz_traction_power_system
I had observed the transmission lines along the former PRR ROW and for some reason thought they were two phases of a three phase system and that the catanary made up the third phase. No. They are a single phase 69 kv to ground 138 kv phase to phase line and a second line on the other side of the ROW. I felt so dumb when I learned that I didn’t know that. Utilities need balanced loads on their 3 phase lines and I should have known better.
As Johny Carsons sidekick used to say, “EVERY THING YOU NEED TO KNOW” is in the wikipedia article.
Back in the early years of electrification, when there were a few three phase electrifications (GN old Cascade tunnel, many lines in Italy), single phase electrifications were specifically called single phase.
While the ex-PRR 25Hz power tramission system is impressive, it is small potatoes compared to the 16 2/3Hz transmission system in Germany. The low frequency was originally used to allow for use of AC series (universal) motors.
Seveal other sites have had various criticisms of the cost over runs for the first phase of the constant tension CAT installation.
-
The replacement of present transmission poles due to their rusting out below grouns level. Using different methods to prolong poles.
-
Related to #1 is that poles are being placed closer than originals. Allows shorter spacing of cross poles that support CAT. That can be explained due to the problem of harmonic oscillations of the CAT under higher speed trains and also that NJT wants to run longer EMU trains with more PANs contacting which could cause possible oscillations.
Pictures of the work seem to show cross beams are being set at a much higher height. May be to allow Amtrak to raise CAT height above rail ? Possible plate “H” clearance ?
- Extra heavy and extra tensioning of guy wires both parallel to tracks and cross wise. Trying to keep constant tension in spec ? Attach poles for weights will need extra guy wires.
Thoughts ?