Alright you juice jacks...

So, they BOTH cannot be conducting electricity simultaneously?

I can understand that if the front has moved to a new circuit while the back is still on the another.

Is the retracted pantograph NOT connected internally and therefore not charged?

Or is is still charged from the front voltage but simply cannot be raised
where it could cause a conflict?

At least on NJT's ALP44's (similar to the AEM7's) and ALP46's - both pans can be raised up and make contact with the wire, but while drawing traciton power, one MUST be isolated - which means, removed from the high voltage "line" running to the main circuit breaker. (im sure there is a much better explaination for that, but thats a "dumbed down" version I was told)

ALP 44's have a bar in the ceiling in the engine room which opens a very large contactor on the roof, physically seperating the high voltage leads that come from each pan. On ALP46's there is a switch, and there is a motorized mechanism that is inside the loco, right near the MCB that isolates the pans from each other

If one pantograph is simply down, and not isolated, its totally energized

Thanks, Shu

Gotta great laugh at your location.... Thanks

Robert Gift wrote:So, they BOTH cannot be conducting electricity simultaneously?

I can understand that if the front has moved to a new circuit while the back is still on the another.

Is the retracted pantograph NOT connected internally and therefore not charged?

Or is is still charged from the front voltage but simply cannot be raised
where it could cause a conflict?

When the AEM 7's were shipped from LaGrange, they had 1 MCB & 1 main transformer connected to it. On the pantograph side of the MCB was the pantograph selector knife switch (Front, Back, or Disconnected / Isolated) with safety interlocks to ensure Both pantographs were down before the switch could be operated (working off the batteries). Also on the pantograph side is the voltage detection circuit to ensure that the cantenary voltage matches the voltage that the operator has selected on the control stand (one at each end) selected to control the unit. If the voltage selected does not match what is on the wire, the incorrect tap connections do alot of damage to the unit if the MCB is allowed to connect to the incorrect cantenary voltage. The unit is designed so only one pantograph can be connected to the MCB. If I remember correctly, The main transformer had 6 taps, 1 for each traction motor, 1 for utilities, and 1 for HEP.
Each pantograph is raised or lowered at the discression of the operator. If the operator lowers the pantograph connected to the MCB, the MCB first opens then the pantograph is allowed to lower, then the unit drops to battery power (64 vdc).
I remember reading in a thread that the AEM 7's are operated with both pantographs up in clear weather. I don't understand why Amtrak subjects the cantenary & unused pantograph shoe to unnecessary wear.

Thanks so much for your wonderful informative post, Tester.

What are 64 V batteries for?
To raise the pantograph on a disconnected engine?

Yes, why would Amtrak raise both unless both are in use and internally connected?
Does it divide power collection through both shoes lessening
wear from amperage draw through just one shoe - if that happens.

Why are all wires on the same railroad not the same voltage?
What complication and potential for damage this causes.

Robert Gift wrote:Thanks so much for your wonderful informative post, Tester.

What are 64 V batteries for?
To raise the pantograph on a disconnected engine?

Yes, why would Amtrak raise both unless both are in use and internally connected?
Does it divide power collection through both shoes lessening
wear from amperage draw through just one shoe - if that happens.

Why are all wires on the same railroad not the same voltage?
What complication and potential for damage this causes.

Thanks so much for your wonderful informative post, Tester.
Your Welcome!!

What are 64 V batteries for?

Same as a Diesel, Control Power to get and keep the systems running

To raise the pantograph on a disconnected engine?
Not to be a smart ass but I never looked at the AEM 7 as an "Engine"

Yes, why would Amtrak raise both unless both are in use and internally connected?

I don't have that answer, but I am sure someone on the Forum does...

Does it divide power collection through both shoes lessening
wear from amperage draw through just one shoe - if that happens.

Only 1 Pantograph connects the main transformer to the cantenary. Each Pantograph has 1 shoe. During nasty weather when Ice & Snow collect on the cantenary, the trailing Pantograph can be utilized to connect the unit to the cantenary and the lead pantograph utilized as a snow plow to remove snow & ice from the cantenary.

Why are all wires on the same railroad not the same voltage?

This is a "relic" of when the line was first built. From what I understand, (and I would like it if someone who has the true story corrects me ) many power companies supplied power along the route or different roads owned the rail.

What complication and potential for damage this causes.

Sorry but I am not sure if this is a question or statement.....

Yes, I previously questioned "engine?".
Locomotive?
But both imply fuel-powered engine.

Yes, previously posted front pantograph acts to scrape ice.

Last sentence was statement commiserating the myriad complications.
I assume the different voltages were from from different railroads.
Just like the problems different guages caused.

Too bad ours is not 5 feet gauge.
My Great Uncle said gauge limited size steam locomotives could attain.

Thanks,

I am sure this will capture the wrath of the Moderator (as I crouch, ducking the flaming arrows) but I read a blurb (and I cannot find the source) that the American Rail track width somehow traces back to the Covered Wagon (not the rail verson, but the Cowboy & Indian Version), that traces back to the Roman Chariot. I always thought it was BS but this is the forum to post the question.........

Ladies????

Gentlemen???

I always thought of the AEM 7 as a bucket of electronic parts that pulled like a SOaB......

Think ive said worse around here there LOCOtester. The other Mod Robert, is pretty layed back also.

My understanding is that it was from the Roman Chariot wheel width.
I assume that measurement was carefully derived from an ideal width of two horses comfortably adjacent to one another.

Wagon makers realized that their wagons would travel more easily in the grooves worn in rock pathways by previous wagons.
So they made their wagon wheel bases conform.

Then, the first "railroads" used the same common off-the-shelf axles rather than go to the time, expense and difficulty of fabricating something different. Maybe they even obtained used wagons and axles with which to experiment. I would!

Robert Gift wrote:My understanding is that it was from the Roman Chariot wheel width.
I assume that measurement was carefully derived from an ideal width of two horses comfortably adjacent to one another.

Wagon makers realized that their wagons would travel more easily in the grooves worn in rock pathways by previous wagons.
So they made their wagon wheel bases conform.

Then, the first "railroads" used the same common off-the-shelf axles rather than go to the time, expense and difficulty of fabricating something different. Maybe they even obtained used wagons and axles with which to experiment. I would!

This goes to show that some things, such as the 4 ft 8 1/2 inches standard gauge, have a long history. Why things are the way they are is a mystery sometimes. But here, the reason for a gauge of 4 ft 8 1/2 inches goes back even further than Roman Chariots – it’s traceable to the first chariots in Mesopotamia.

It turns out the best width for chariot wheels is the related to the width of the two horses to put the chariot.

So, like some things, it's traceable to a pair of horses a$$es.

First Barnegat wrote: So, like some things, it's traceable to a pair of horses a$$es.

That is the general accepted belief of railroaders - always looking at the hind end of the head end if you know what i mean!!!

NJT and Im sure Amtrak refers to their Electric locomotives (AEM7, HHP8's, ALP 44's and 46's) unofficially as MOTORS. "Engine" tends to refer to a diesel locomotive

For example, you would hear "Check the pan on the motor" - you wouldnt' really hear "check the pan on the engine" But of course, if somone said that, it would be understood what they were referring to (the electric locomotive)