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#1 acelafan

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Posted 29 July 2009 - 08:27 PM

Probably a very simple answer to this question...but I'm sure others who have ridden the NEC might have noticed the head end power (lights/ac) might go out in the coach cars for 10, 20, or 30 secs on rare occasions. I've experienced this situation on both the Acelas & the NE Regionals. Does this mean there is a dead spot in the electrical catenary wires? If the train were moving very slowly and it hit one of these "dead spots" - could it cause the locomotive to lose power and thus effectively make the train stranded on the tracks? Would Amtrak then need to tow it to a section of electrified wire?

#2 battalion51

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Posted 29 July 2009 - 08:31 PM

There are certain places along the corridor that are designated dead spots. There are signs for these dead spots. Engineers know where these are and always have enough momentum behind them to get through the dead spot.

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#3 Dutchrailnut

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Posted 29 July 2009 - 08:39 PM

Probably a very simple answer to this question...but I'm sure others who have ridden the NEC might have noticed the head end power (lights/ac) might go out in the coach cars for 10, 20, or 30 secs on rare occasions. I've experienced this situation on both the Acelas & the NE Regionals. Does this mean there is a dead spot in the electrical catenary wires? If the train were moving very slowly and it hit one of these "dead spots" - could it cause the locomotive to lose power and thus effectively make the train stranded on the tracks? Would Amtrak then need to tow it to a section of electrified wire?



yes on NEC there are several phase breaks or phase gaps were a locomotive momentairy loses the power, prime exaples are cos cob bridge were a 90 foot gap exist for the bridge to be raised.
normally a train will just coast through such power interuptions but once in a while a locomotive has bad batteries and goes in emergency , so there will be need for a tow.

#4 acelafan

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Posted 29 July 2009 - 09:36 PM

Cool, thanks for the replies. Always wondered about that.

#5 Acela150

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Posted 29 July 2009 - 09:37 PM

I notice this a lot on Regionals not Acela. Cause Acela has two pans up with the Regionals just the one or sometimes two. But do DC AEM-7's go up to BOS or just the AC's?
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#6 Guest_Gord_*

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Posted 29 July 2009 - 10:34 PM

Probably a very simple answer to this question...but I'm sure others who have ridden the NEC might have noticed the head end power (lights/ac) might go out in the coach cars for 10, 20, or 30 secs on rare occasions. I've experienced this situation on both the Acelas & the NE Regionals. Does this mean there is a dead spot in the electrical catenary wires? If the train were moving very slowly and it hit one of these "dead spots" - could it cause the locomotive to lose power and thus effectively make the train stranded on the tracks? Would Amtrak then need to tow it to a section of electrified wire?



yes on NEC there are several phase breaks or phase gaps were a locomotive momentairy loses the power, prime exaples are cos cob bridge were a 90 foot gap exist for the bridge to be raised.
normally a train will just coast through such power interuptions but once in a while a locomotive has bad batteries and goes in emergency , so there will be need for a tow.


There are also "section insulators" spaced at regular intervals that allow sections of overhead to be electrically isolated for maintenance, repair and emergencies. They may also be used where the feed from one substation ends and the next begins or at the doors of shops or carhouses to isolate the track within to protect workers.

Variations of these section insulators are used on light rail and streetcar operations as well. With operations using regenerative braking, provision has to be made to prevent a unit in regen mode from energizing a dead line if it is braking while entering the de-energized section.

I'm just a rail mechanic and I'm sure we have some electrical engineers out there who are able to provide a more detailed explanation.

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#7 Dutchrailnut

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Posted 30 July 2009 - 06:27 AM

I notice this a lot on Regionals not Acela. Cause Acela has two pans up with the Regionals just the one or sometimes two. But do DC AEM-7's go up to BOS or just the AC's?



The Pantographs on Acela are not connected, each power head is independent and only one of them supplies HEP at any time.
So Acela is effected by same power losses.

Section insulators do not drop the power, since they have same phasing and have a wire extender at each side of them, only thing you see is a small arc when a pantograph passes.

#8 BLOND37

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Posted 30 July 2009 - 07:01 AM

There was another thread about scary spots or something. Have to admit I always breath a sigh of relief when the lights and air come back on after a dead spot!
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#9 battalion51

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Posted 01 August 2009 - 09:10 PM

I notice this a lot on Regionals not Acela. Cause Acela has two pans up with the Regionals just the one or sometimes two. But do DC AEM-7's go up to BOS or just the AC's?



The Pantographs on Acela are not connected, each power head is independent and only one of them supplies HEP at any time.
So Acela is effected by same power losses.

Section insulators do not drop the power, since they have same phasing and have a wire extender at each side of them, only thing you see is a small arc when a pantograph passes.

I believe the reason Acela doesn't drop the power is because they were built with a battery system that will hold the HEP for a few moments when you go through a phase change. With fixed trainsets, this is pretty easy to do. One of the few things they did right with Acela...

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#10 jis

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Posted 01 August 2009 - 10:56 PM

I believe the reason Acela doesn't drop the power is because they were built with a battery system that will hold the HEP for a few moments when you go through a phase change. With fixed trainsets, this is pretty easy to do. One of the few things they did right with Acela...

Acelas do drop HVAC, but not lights, which suggest to me that they have some battery arrangement for lights only in each car. This is very common practice almost everywhere other than in North America. It is only in here that I have come across lighting systems in cars that are not supported by adequate battery backup to keep on for a considerable amount of time.

#11 Green Maned Lion

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Posted 02 August 2009 - 12:27 AM

There was another thread about scary spots or something. Have to admit I always breath a sigh of relief when the lights and air come back on after a dead spot!


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#12 AlanB

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Posted 02 August 2009 - 01:35 AM

But do DC AEM-7's go up to BOS or just the AC's?


Regionals can be pulled by either and AEM-7 or an HHP-8 to Boston.
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#13 jis

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Posted 02 August 2009 - 10:52 AM

I notice this a lot on Regionals not Acela. Cause Acela has two pans up with the Regionals just the one or sometimes two. But do DC AEM-7's go up to BOS or just the AC's?

As mentioned by Dutch, only one of the two pans in Acela supplies HEP. The two power heads are electrically isolated from each other. Otherwise there would be havoc when one pan is on one phase and other on a different one as the train passes a phase gap.

Acleas just have more ergonomically designed battery backup for the car lights than the Amfleets do.

The DC and AC in AEM-7s refers to the type of motor and drive system that it has and not the power that it collects from the catenary. All of them - irrespective of DC or AC are capable of operating under 11kV 25Hz, 12kV 60Hz and 25kV 60Hz AC catenary systems. So yes, all of them can go to Boston.

#14 acelafan

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Posted 02 August 2009 - 01:09 PM

I notice this a lot on Regionals not Acela. Cause Acela has two pans up with the Regionals just the one or sometimes two. But do DC AEM-7's go up to BOS or just the AC's?

As mentioned by Dutch, only one of the two pans in Acela supplies HEP. The two power heads are electrically isolated from each other. Otherwise there would be havoc when one pan is on one phase and other on a different one as the train passes a phase gap.

Acleas just have more ergonomically designed battery backup for the car lights than the Amfleets do.

The DC and AC in AEM-7s refers to the type of motor and drive system that it has and not the power that it collects from the catenary. All of them - irrespective of DC or AC are capable of operating under 11kV 25Hz, 12kV 60Hz and 25kV 60Hz AC catenary systems. So yes, all of them can go to Boston.


What is the reason for the differing voltages/cycles on the NEC? Purely historical? Hypothetically speaking, if Amtrak were to extend electrification down to say, Richmond VA for higher-speed rail, what electrical specifications would like they be likely to choose for the catenary? Would they choose the same specs for other areas of the country or do several variables come into play?

#15 jis

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Posted 02 August 2009 - 01:41 PM

What is the reason for the differing voltages/cycles on the NEC? Purely historical? Hypothetically speaking, if Amtrak were to extend electrification down to say, Richmond VA for higher-speed rail, what electrical specifications would like they be likely to choose for the catenary? Would they choose the same specs for other areas of the country or do several variables come into play?

Differences are purely historical. Any new electrification will use the 25kV 60Hz AC system, just as was done New Haven to Boston.

#16 Crescent ATN & TCL

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Posted 03 August 2009 - 11:20 PM

What is the reason for the differing voltages/cycles on the NEC? Purely historical? Hypothetically speaking, if Amtrak were to extend electrification down to say, Richmond VA for higher-speed rail, what electrical specifications would like they be likely to choose for the catenary? Would they choose the same specs for other areas of the country or do several variables come into play?

Differences are purely historical. Any new electrification will use the 25kV 60Hz AC system, just as was done New Haven to Boston.


Is there any reason Amtrak can't switch the NEC to 25kV 60Hz AC along the whole route as electrical equipment is replaced?

#17 AlanB

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Posted 04 August 2009 - 12:24 AM

What is the reason for the differing voltages/cycles on the NEC? Purely historical? Hypothetically speaking, if Amtrak were to extend electrification down to say, Richmond VA for higher-speed rail, what electrical specifications would like they be likely to choose for the catenary? Would they choose the same specs for other areas of the country or do several variables come into play?

Differences are purely historical. Any new electrification will use the 25kV 60Hz AC system, just as was done New Haven to Boston.


Is there any reason Amtrak can't switch the NEC to 25kV 60Hz AC along the whole route as electrical equipment is replaced?


Start with money, then move to the fact that it's not like one can just convert one small section at a time. You pretty much have to convert the entire corridor at once. Add to that equation that you've still got Metro North in the middle.
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#18 jis

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Posted 04 August 2009 - 07:44 AM

Start with money, then move to the fact that it's not like one can just convert one small section at a time. You pretty much have to convert the entire corridor at once. Add to that equation that you've still got Metro North in the middle.

I think the real issue is money. Also it seems to me that of the various possible combinations the one that MNRR has chosen probably makes the best use of any available money, i.e. convert to commercial frequency and constant tension. Commercial frequency so that it takes Amtrak out of the business of maintaining its own conversion facilities and constant tension to enable higher speed and require fewer heat related speed restrictions. Not going to 25kV avoids the problem of dealing with creating additional clearance in tight areas which could cost a pretty penny in civil engineering work.

Note that even without changing the voltage it is taking MNRR over 15 years to complete the conversion of their section. Strictly speaking the corridor is electrically segmented and the conversion could be done segment by segment. If voltage is not changed such a method will work even in areas where Arrow IIIs and Silverliners operate, which do not have automatic tap changin facilities to allow automatic changeover from 12kV to 25kV and back.

#19 acelafan

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Posted 04 August 2009 - 08:22 AM

Note that even without changing the voltage it is taking MNRR over 15 years to complete the conversion of their section.


So MNRR will have constant tension cat from end-to-end in their domain of the NEC? Will Amtrak be able to capitalize on that improvement for faster speed or will other upgrades need to occur first? Granted I am sure the speed increases wouldn't be huge, but shave a minute here, a minute there and it all adds up.

#20 jis

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Posted 04 August 2009 - 08:41 AM

So MNRR will have constant tension cat from end-to-end in their domain of the NEC? Will Amtrak be able to capitalize on that improvement for faster speed or will other upgrades need to occur first? Granted I am sure the speed increases wouldn't be huge, but shave a minute here, a minute there and it all adds up.

AFAIK no speed changes are planned for the MNRR section of the NEC, and yes MNRR will have CT catenary end to end when they are done.



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