25 Hz power stated as challenge to opening NYP tunnels

[oltmannd]

John WR

Thanks for your explanations, Erik.  If I understand you correctly the Pennsylvania choose 25 Hz because it was available at the time and needed only a step down transformer to directly power it traction motors.  At 60 Hz back emf is a real problem but at 25 Hz it is not.  DC was rejected because of the expense involved in converting AC to DC.  

But in the 1960's when Amtrak electrified the line between New Haven and Boston solid state electronics made it much easer and cheaper to convert AC to DC.  In fact the conversion could be done on board the train itself.  And a 25 Hz motor may be run on DC.  At the same time 60 Hz uses much smaller transformers and is converted to DC as easily as 25 Hz is.  So Amtrak chose 60 Hz at high voltage and step it down and convert it to DC on the train to run DC motors.  

The reason Amtrak has not converted to 60 Hz and DC motors south of New Haven is because opponents in the Congress will not grant Amtrak the funds it needs to modernize.  

I'll add a bit here.  Way back, at the dawn of Conrail, there was quite a bit of work done trying to figure out the future of the PRR & NH electrification.  One piece was a study to extend the wire to Pittsburgh (Conway Yard).  That would have been  60Hz since that was the state of the art at that point.  It was pretty clear at that point the the days of 25Hz were ending, but there would be a transition period to manage through.   The hydro power on the Susquehanna and all the rotary converters were in rough shape - the result of PRR and PC having no money to spend for a couple decades.  The Cos Cob generating station on the NH was wheezing, underpowered and failing regularly.  NJDOT/NJT had their ancient Lackawanna 3000 VDC system to update with a desire to start direct service to Penn Sta and a desire to extend the wire on the NY&LB (North Jersey Coast) to Red Bank as the commuter population in that area grew to avoid all those engine changes at South Amboy.

There was the problem of figuring out what to do with the electric locomotive fleet.  For a whole bunch of reasons, the GG1s needed to be replaced.  There was Federal funding for a couple of demo locos from EMD plus some money to convert an E44 to dual voltage/dual frequency.  Amtrak has spec'd out and taken delivery of their ill-fated E60s.  These were capable of running on 25Hz or 60 Hz  and a variety of voltages.  The AEM7s came on in 1979/80 similarly equipped.  The Metroliners went out for rebuild and came back ready to handle 25 or 60Hz and various voltages.

The dominoes started to fall.  MN just couldn't wait and went first, finally retiring Cos Cob and going with 12,500 VAC, 60 Hz.  Amtrak was ready to go.   NJT converted the Lackawanna to 60Hz AC, retiring the old DC MUs, and extended the NJ&LB wire to Matawan using 25Hz, but beyond that, went with 60Hz.  

Amtrak was planning on ditching all the 25Hz equipment, but the advent of solid state converters and the lack of money for conversion stalled things out.  They did a ton of modernizing on the south end of the NEC, installing concrete ties and new rail, CTC and a pilot solid state power supply.  But, after that, the money dried up and the focus changed to the NH-Boston section of the NEC and acquiring the Acela train sets.

And.... here we are.

[blue streak 1]

MidlandMike

John WR

...

But in the 1960's when Amtrak electrified the line between New Haven and Boston ...

I'm not sure if this was a typo, the line was converted in the late 1990s.  The following link has a review of early RR electrification supply systems, recent electric system conversions, and some thoughts for the future:

  http://www.ltrc.lsu.edu/TRB_82/TRB2003-001318.pdf

activated

[MidlandMike]

henry6

MidlandMike

blue streak 1

MidlandMike

I get the impression Amtrak would like to upgrade the entire system to 60 Hz to avoid future problems like this emergency compatibility, but (according to another railfan forum) SEPTA is the final holdout.

SEPTA may / should not be a big problem as the silverliner - 5s are being built to work on both 25 and 60 Hz...

SEPTA might not object to ATK modernizing the lines they both run on, however, wouldn't SEPTA also have to modernize their own suburban lines as all the operations are integrated?

But SEPTA Rail  already has integrated their electric operations so all equipment seems to run on former PRR and former RDG tracks.

I'm guessing the equipment can handle 60 Hz, but the EMUs might have problems with the on-route voltage change from 12.5 Kv to 25 Kv.  I believe NJT has a similar problem on the North Jersey Coast line

[henry6]

MidlandMike

I'm guessing the equipment can handle 60 Hz, but the EMUs might have problems with the on-route voltage change from 12.5 Kv to 25 Kv.  I believe NJT has a similar problem on the North Jersey Coast line

NJT has to change power from Morristown/Montclair line trains at Kearny Jct to the Corridor and at Matawan on the NJCL to Long Branch..

[timz]

Which is why NJT doesn't use EMUs on those trains.

[henry6]

TIMZ, I presume you are talking MidTown Direct.  Which, yes, are locomotive driven, or push pull,  trains.  BUT, trains from Matawan and South Amboy can be either push pull or EMU as all trains from Trenton.  BUT ALSO, there are several EMU sets on the Hoboken Division (normally) for runs Hoboken to Montclair, Summit, Gladstone and Dover but not for Mid Town Direct Service.

[John WR]

Not really a typo, Mike, but when I said Amtrak electrified the line in the 1960's I guess I was confused.  Amtrak did not even exist in the 1960's.  I went back and changed my original statement.  Thanks for pointing out this error.  

[Phelps]

Lots of people have very nicely given the theory and history of the use of 25 Hz; I don't need to repeat it.  However, discussion of SEPTA (and to some extent NJT) seems to overlook a bit of history that, as it happens, I personally participated in.

At the time the cars that became the Siverliner IVs and Jersey Arrow IIs were being specified, there were firm plans to convert the former Reading lines to 25 Kv, 60 Hz, and the eventual use of 12.5 kV, 60 Hz in various places was pretty well established.  Accordingly, the specifications required that those two fleets be capable of operating on any of the three possible combinations - (then) 11 kV, 25 Hz, 12.5 kV 60 Hz, and 25 kV, 60 Hz.  Those Silverliners that were to run on the (converted) Reading lines had to have "on the fly" changeover capability.  The main transformers were designed with two primary windings, to be connected in parallel at the lower voltages and in series for the higher voltage.  The greater losses at 60 Hz were compensated for by the higher nominal voltage (the change to higher nominal at 25 Hz came later, as one commenter pointed out). 

By the time the cars were actually delivered, the plans to make the Reading 25 kV had fallen through, but GE did develop and test on one car the automatic changeover system.  Yours truly, together with one other GE engineer, received a patent for the system (which has long expired; the system now in use on the NEC works generally the same way as the GE system, with some refinements made possible by the evolution of technology since the early '70s).  Now, again as someone pointed out, the changeover on the EMUs is made, if necessary, by manually cranking the changeover shaft from one position to the other (the power contacts are inside the transformer tank).

The "M-(even number)" series cars on MN (ex NH lines) have a 60 Hz-rated transformer that is designed not to saturate at 25 Hz, but only one primary winding, so they can't operate at 25 kV.  The exception is the newest, the M-8s, which are dual voltage.

The folks who explained the history of 25 Hz did a great job, by the way, thanks!

Dave Phelps

[blue streak 1]

Phelps

  Now, again as someone pointed out, the changeover on the EMUs is made, if necessary, by manually cranking the changeover shaft from one position to the other (the power contacts are inside the transformer tank).

The "M-(even number)" series cars on MN (ex NH lines) have a 60 Hz-rated transformer that is designed not to saturate at 25 Hz, but only one primary winding, so they can't operate at 25 kV.  The exception is the newest, the M-8s, which are dual voltage.

Dave Phelps

Dave;  thanks for the info.  a few questions about the silverliner - IVs / arrow - IIs since they were specified somewhat earlier than the -Vs.

1. where do the outputs of the transformer go ? Rectifiers or do some go directly to auxilaries ?

2. type traction motors ?

     a. any difference in acceleration?

3. did lighting look different on the different frequencies ?  

4. NOTE;  All AMTRAK reports etc now specify the 25 Hz as 12.0 Kv.

5. There has been some debate whether the M-8s could operate on 25 Hz but you suggest they could ?

6. Of course the M-8s can also operate on the under running DC out of grand central terminal.

7. if the earlier Ms are not retired first could they be retrofited for dual voltage ?

[daveklepper]

I'll leqve it to Dave Phelps to answer the above question accurately, but my understanding is that the new M-8's cannot run on 25Hz, because in design it was decided that the transformers would occupy too much space and be too heavy.  They can, I believe, switch automatically between 12,500 and 25,000 volts.

But a major correction to an earlier posting is required.  The first big step in chaning ac locomotives was moving to rectivication and using pure dc motors instead of 25Hz (or 16.5Hz in Europe) ac commutator motors.   Thus the "Jets" (NYNH&H EP-5's), the Virginian and PRR post-WWII electric freight locomotives, the Washboards (4400's), and the early Silveliners, possibly up to Silverliner-4's.   But now all modern electric railway equipment, from streetcars to European freight electrics have a development paralleling that of the most efficient diesels, and use ac non-synchronis, slanted bar (as opposed to the bars in squirel-cage) hysterisis motors.  As on ac diesels, this eliminates brushes and commutators and their wear.   The ac is rectified to dc, then converted back to ac at the Hz corresponding to the speed of the motor plus slippage.  The M-8's use such motors and so do the latest Silverliners, and of course Acela and Bombardie Amtrak locomotives, the NJT dual-modes, etc.  Some of the Amtrak Swedish Meatballs or Toasters have been converted.   Indeed, Metro North and LIRR even had some FL-9's upgraded with such motors!

[John WR]

But Dave, don't asynchronous motors have a drawback in that the electronics needed to convert AC to DC and then back to AC again requires a certain amount of maintenance that a single conversion to DC with series wound DC motors does not need?

[erikem]

The inverters usually don't require much maintenance beyond keeping the cooling system working. There is nothing mechanical to wear out, where DC series motors have commutators and brushes that wear. An AC induction or synchronous motor is typically cheaper for a given power output than a DC motor as well as being smaller, lighter and more rugged. We may soon see DC motors as an extra cost option on locomotives as opposed to being a lower cost option.

- Erik

[daveklepper]

The inverters and their controls are electronic devices that require the sort of maintenance that a high quality stereo or tv set requires.   The DC motors running off an ac catenary required tap-changing transformer contactors or the same sort of electronic control on the voltage output of the rectifier system that the inverter control requires.   So there is absolutely no cost advantage in maintenance for dc motors over ac regarding the control system and considerable maintenance saving for the motors.

[henry6]

Wed. Nov 14th AMtrak news release with co sponsor  NJT, says they feel the Kearny Substation will be online and in service on Friday...this will increase catanary  power as well as signal and switch power.  Therefor there can be an increase in the number of trains being handled on both the Corridor and trhough the East river tunnels to Sunnyside Yard.  No new schedules posted...but MNRR is complete, LIRR is busing the Long Beach Branch and east of Riverhead and still modified schedules (reduced services) on most lines, especially east to Montauk., NJT has modified (reduced) schedules on all lines except the NJCL which is hoped to have some kind of service by this weekend..  

[John WR]

Meanwhile another nor'easter is predicted for the middle of next week although it is not predicted to be as strong or cold as the last one.  It could cause problems over Thanksgiving.

[oltmannd]

John WR

But Dave, don't asynchronous motors have a drawback in that the electronics needed to convert AC to DC and then back to AC again requires a certain amount of maintenance that a single conversion to DC with series wound DC motors does not need?

With the AC to DC machine, you need to control the voltage to control the power and speed.  This was typically done with tap switches on the transformer - so you have lots of high power switch gear and a control system to operate it.    With the AC-DC-AC machine, the DC buss is maintained at a constant voltage and it's chopped back into variable frequency AC by inverters.  Much less mechanical machinery involved.

[John WR]

Don,  

I am not entirely unfamiliar with the difference between alternating current and direct current as they are applied to motors.  However, in April of 2010 Don Graab wrote an essay for Trains.  He argued that asynchronous motors produced high torque at low speeds and were particularly valuable for pulling long heavy trains.  However, at high speeds there was little or no advantage and, since the electronics were more expensive, many freight railroads used DC motors for that job.  Of course technology can change fast these days so what was true 2 1/2 years ago may no longer be true today.  

Here is a link to the essay:  http://trn.trains.com/en/Railroad%20Reference/Locomotive%20Profiles/2010/04/AC%20traction%20a%20motive%20power%20bosss%20perspective.aspx

[blue streak 1]

IMHO the solution should be a long term operation. One way would be to gradually remove the 25 Hz equipment in a section at a time with new 60 Hz equipment.  Move the 25 Hz equipment that still has some life left to in service 25 Hz locations that needs replacing. That way no new 25 Hz equipment would be bought ? Maybe even some given to SEPTA ?

consideration would be needed to convert those lines where all in service rolling equipment can use 60 Hz.

1. The primary generators for 25 Hz is at Safe Harbor with the transmission lines from there to Harrisburg, Perryville, and Atglen ( on to Trenton & PH).  That may be the last section feeds to be converted.

2. Newark - Trenton is going to be the first to get a rebuilt constant tension CAT by 2017 so maybe that line along with continuing to NYP & Sunnyside might be first especially since the voltage would go from 12.0 Kv to 12.5Kv. That would give a silght increase of power capability carried by the CAT for the higher speeds that have already been tested. AMTRAK also want to abandon the 25 Hz primary that runs along the PRR old Trenton cutoff.

3. Harrisburg - ATGLEN  might be another shorter segment

4. Perryville -  WASH might be a good segment as all MARC electric can use 60 Hz either 12.5 Kv or 25 Kv.