The announcement of a joint procurement of hHSR train sets had 2 very interesting points. Here is a snippet of the AMTRAK statementi
"" In addition, the preferred train set has Electric Multiple Unit (EMU) power distribution among all cars, operates bi-directionally with a cab car on each end that allows for passenger occupancy and has a seating capacity of 400 to 600 passengers. ""
Using EMU power distribution is most important for AMTRAK. The potential for quicker acceleration and deccelaration will enable AMTRAK to operate on the NEC quicker with its many slower sections. IMO the EMU operation vs a locomotive / motor would probably save 10 - 15 minutes on the NEC NYP - WASH at the present time ?? AS each NEC slow section is eliminated the timekeeping will naturally improve. Note also the press release says that the first new trains will be for additional service.
Also note the apparent increase of AMTRAK passenge capacity to 600. That would almost double the present ACELA' s 300 + passengers instead of the dropped proposal of adding 2 business class coaches to present ACELAs. So will this be called a "Super ACELA"?
The need for much smaller HP traction motors under each car would reduce the unsprung weight on axels that many of you posters have noted causes problems. will reduce track maintenance.
CA HSR will not get as much benefit from the EMU traction setup since most of its ROW will be built to either 220 where easy or 160 MPH at difficult places ?
One result of the 160 MPH tests may be this decision to get EMU type traction. How many contact PANs will be on the trains is anyone's guess.
Here is the AMTRAK RELEASE;
http://www.amtrak.com/ccurl/620/710/Amtrak-CHSRA-Joint-RFI-HSR-Train-Sets-ATK-13-012.pdf
The benefits of multiple units--the ability to tailor power to the weight of the train and the fact that with several traction motors each one is much lighter than a single or double one would be--have long been known. I wonder why these were not incorporated into the present day Acela.
California is a single state which an make a single decision for high speed rail on a line that will ultimately be 800 miles long. No state on the northeast corridor can possibly do that. New York could do it between New York City and Buffalo and Pennsylvania could do it between Philadelphia and Pittsburgh. However, I guess they are still not inclined to do so.
Several more points.
1. Bi - directional
a. NEC -- BOS, NYP, WASH--- PHL for turns to HARRISBURG
b. CA -- SACREMENTO, SFO new transbay terminal, SAN DIEGO, LAX until run thru at station is built
2. Cab cars with seating -- keeps train sets shorter for given capacity especially important at NYP until new tunnels and expansion of station is built.
3. Wonder if the CA trains will uses the same transformer that will be needed for the NEC 25 Hz ? note ; 25 Hz transformer will work on 60 Hz but 60 Hz cannot work on 25 without major degregation.
Good point about 60 Hz vs 25 Hz. Amtrak will never be able to buy "off the shelf" until they convert to 60 Hz.
MidlandMikeGood point about 60 Hz vs 25 Hz. Amtrak will never be able to buy "off the shelf" until they convert to 60 Hz
But with today's electronic converters all kinds of conversion seems simple. Right now some systems take AC, convert it to DC in the locomotive and then convert it back to some other AC frequency often with a square wave.
In the northeast Amtrak still used some electromechanical converters because it has them. But as time goes on it has to replace them with electronic converters.
MidlandMike Good point about 60 Hz vs 25 Hz. Amtrak will never be able to buy "off the shelf" until they convert to 60 Hz.
It's just the transformer. Amtrak ran an "off the shelf" Rc4 (AEM7), X2000 train set, ICE (gen 1) trainset. These were all returned to Europe and placed in service there. Couldn't be a huge deal....
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmannd It's just the transformer. Amtrak ran an "off the shelf" Rc4 (AEM7), X2000 train set, ICE (gen 1) trainset. These were all returned to Europe and placed in service there. Couldn't be a huge deal....
blue streak 1 How many contact PANs will be on the trains is anyone's guess.
How many contact PANs will be on the trains is anyone's guess.
Right now on MU's it is common to run married pair cars that have a pantograph on every other car.
John WR MidlandMikeGood point about 60 Hz vs 25 Hz. Amtrak will never be able to buy "off the shelf" until they convert to 60 Hz But with today's electronic converters all kinds of conversion seems simple. Right now some systems take AC, convert it to DC in the locomotive and then convert it back to some other AC frequency often with a square wave. In the northeast Amtrak still used some electromechanical converters because it has them. But as time goes on it has to replace them with electronic converters.
And the reason to buy and maintain this extra layer of electronics, is why?
Not sure about which layer of electronics you were referring to, so will attempt to answer both.
Converting from (single phase, fixed voltage and frequency) AC to DC and then back to (three phase variable voltage and frequency) AC is to use of induction motors. Chances are you already knew that.
Converting from three phase 60 Hz to single phase 25 Hz is to accommodate the existing catenary and related power distribution equipment. For a given voltage, more power can be delivered to a train at 25 Hz than at 60 Hz, due to the effects of inductive reactance (scales with frequency) and skin effect (scales with the square root of frequency). In the short term, it may be cheaper to replace the rotating frequency converters with static converters than to replace the catenary and associated electrical gear.
- Erik
Perhaps I am missing something, Erik. All of the jumping back and forth between 60 and 25 boggles my mind.
I understand that the New Haven Railroad when it electrified between New York and New Haven set up the system to use 25 Hz and that that time 25 Hz was easily available.
Today it is not available or it is less available so Amtrak has to deal with that. They deal with it by converting from 60 Hz to DC to 25 Hz because that is the most practical way to do it.
Am I wrong on this?
John WR Today 25Hz is not available or it is less available so Amtrak has to deal with that. They deal with it by converting from 60 Hz to DC to 25 Hz because that is the most practical way to do it. Am I wrong on this?
Today 25Hz is not available or it is less available so Amtrak has to deal with that. They deal with it by converting from 60 Hz to DC to 25 Hz because that is the most practical way to do it.
afraid so --- no DC INVOLVED
3 ways now ---
1. The old PRR method using what is called a rotary converter which looks like an overgrown motor without any shaft but just 60 Hz wires in and 25 Hz out.
2.. Motor generator sets 60 Hz electric motor connected by shaft to a 25 Hz generator.
note; both #s 1 & 2 rotate at a common divisor speed of 3600 & 1500 ( freq times 60 RPM times electric frequency ). (highest speed 300 RPM next 150 RPM)
3. A solid state converter --- method or mechanism unknown.
MNRR changed the NH route to 60 Hz due to failures of COS COB power station. The change over was much simpler than a conversion of the PRR section will be due to much more PRR equipment tied to25 Hz. Even so it took over 2 weekends and a full week to complete. That was just the time there was no electric service by MNRR or AMTRAK only diesel. EMUs were started converting a month or so before and were not completed for almost 2 months. Someone have more details ?
there was a long thread a year or more ago that went into this in detail
erikem ... Converting from three phase 60 Hz to single phase 25 Hz is to accommodate the existing catenary and related power distribution equipment. For a given voltage, more power can be delivered to a train at 25 Hz than at 60 Hz, due to the effects of inductive reactance (scales with frequency) and skin effect (scales with the square root of frequency). In the short term, it may be cheaper to replace the rotating frequency converters with static converters than to replace the catenary and associated electrical gear. - Erik
...
I am guessing you are right about it being cheaper to replace the rotary converters than to change the cat, which is probably why Amtrak did that and put off their planned frequency and cat change. Nevertheless, the present fixed cat is not appropriate for high speed, and will eventually need upgrading. In the meantime they must deal with all the 25 Hz obsolescence problems.
blue streak 1 John WR Today 25Hz is not available or it is less available so Amtrak has to deal with that. They deal with it by converting from 60 Hz to DC to 25 Hz because that is the most practical way to do it. Am I wrong on this? afraid so --- no DC INVOLVED 3 ways now --- 1. The old PRR method using what is called a rotary converter which looks like an overgrown motor without any shaft but just 60 Hz wires in and 25 Hz out. 2.. Motor generator sets 60 Hz electric motor connected by shaft to a 25 Hz generator. note; both #s 1 & 2 rotate at a common divisor speed of 3600 & 1500 ( freq times 60 RPM times electric frequency ). (highest speed 300 RPM next 150 RPM)
The PRR used #2, the rotary converters (AKA synchronous converters) were used for converting AC to DC. "Motor generator set" is slightly misleading, they're actually two synchronous machines that can act as either a motor or generator. Most of the time the 60 Hz machine is the "motor" and the 25 Hz machine is the "generator".
25 Hz is too close to 60 Hz for a cycloconverter to work well, the 1:3 ratio in Europe is more conducive to cycloconverter operation. FWIW, a cycloconverter does a direct conversion of one AC frequency to another that is 1/3 or less of the first frequency.
I would strongly suspect that static (i.e., no moving parts) converters do transform to DC then back to AC. One reason is giving a well balanced three phase load and another is allowing more freedom in ratio of input and output frequencies. FWIW power companies make use of AC to DC to AC interties to allow power to be transferred asynchronously between two grids (such as between the west coast and east coast, though GE has developed a phase shifting transformer that may be more efficient.
Is there any equipment left on the NEC that is not dual-frequency? Perhaps, as the new cat is strung, it could be powered by the same freq and voltage as the north end of the NEC.
I seem to remember that the NJT Arrows can't switch on the fly. Perhaps they could be restricted to Hoboken trains.
I think it is great Amtrak is finally setting standards on HSR trainsets, Corridor Cars and hopefully soon Commuter cars. If we get one basic nationwide design we all save substantial taxpayer money on the orders and maintenence, IMO. No restriction on the amount of tweaks to the platform but the basic platform should be the same across the country, IMHO.
erikem One reason is giving a well balanced three phase load and another is allowing more freedom in ratio of input and output frequencies. FWIW power companies make use of AC to DC to AC interties to allow power to be transferred asynchronously between two grids (such as between the west coast and east coast, though GE has developed a phase shifting transformer that may be more efficient. - Erik
One reason is giving a well balanced three phase load and another is allowing more freedom in ratio of input and output frequencies. FWIW power companies make use of AC to DC to AC interties to allow power to be transferred asynchronously between two grids (such as between the west coast and east coast, though GE has developed a phase shifting transformer that may be more efficient.
oltmannd Is there any equipment left on the NEC that is not dual-frequency? Perhaps, as the new cat is strung, it could be powered by the same freq and voltage as the north end of the NEC. I seem to remember that the NJT Arrows can't switch on the fly. Perhaps they could be restricted to Hoboken trains.
Reasonable questions.
The 25 Hz power is generated by three phase alternators connected to produce single phase, the same way the 25 Hz plants owned by the New Haven, N&W and Virgininian were set up. There were slight modifications made to the alternators to accommodate the phase imbalance.
The 25 Hz power on the PRR is transmitted as single phase, the plus/minus 69kV arrangement is to both minimize the insulation requirements and to keep currents in the conductors balanced to minimize unwanted inductive effects (i.e. where current is induced in other conductors, e.g. telephone lines). The PRR had multiple circuits for redundancy, each pair of wires was one circuit.
I don't think the PRR used autotransformers, as those are more appropriate with a 2:1 voltage ratio as used on the New Haven.
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