What determines if the front or rear pantograph goes up?

Hi,

I've always wondered what determines what pantograph on NEC electric locos go up. There is always a pare of them and on all the locos I've seen lately, the rear pantograph is up with respect to the trains direction.

I know when the E60 was first delivered, it ran with its from pan up but in its later years it ran with the rear pantograph up, primarily. Every now and then I'll see an AEM7 with the fron pantograph up which looks wierd to me, lol, but the AEM7s and HHPs mostly run with rear pans up. Septa's AEM7s always run like that.

With the Acelas its been back and forth. Sometimes the front pans are up and other times the rear pan is up.

Can anyone explain what determines which pantograph is raised?

Thanks. Looking forward to your responses!!!!!

An explanation I once heard was that the rear pan is used, so that in the case of the pan fouling with the catenary, there's a chance that the front pan might be able to contact the wire and provide power to pull the train through. Now, on locomotives, that's probably not likely, as any entanglement is likely to have rendered the entire section of catenary over the locomotive useless. I'll add that something tells me that this was reading practice with their MUs, which featured a traction power bus that trainlined power to all the MUs in a consist, thus only requiring one pan per train to be up (as opposed to a pan for each MU). If you had several MUs, all with pans, the above explanation becomes more plausable.

but sometimes, when there is ice on the catenary, only the leading pan is up just in case if that one breaks off, there will still be a pantograph left on the rear engine

On the AEM-7, at least pre rebuild, you could unbus the pans for sleet scrapping, to limit arcing at the front.

Historically, RRs operated with the rear pan up. This doesn't apply with newer EMUs, or on a lot of stuff in Europe where there's only one pan per loco for a given system - multisystem locos can have as many as 4 different pans on them.

It was explained by one of the engineers on the last board that the rear pan is put up so that if it gets caught and the pan comes apart, it won't come apart and damage the other pan. If the front pan was up, the pieces would hit the lowered rear pan thus loosing both of them.

Olton Hall wrote:It was explained by one of the engineers on the last board that the rear pan is put up so that if it gets caught and the pan comes apart, it won't come apart and damage the other pan. If the front pan was up, the pieces would hit the lowered rear pan thus loosing both of them.

Thanks -- that's the logic explainin what I had heard.

newer EMU's, what does EMU stand for?

Nasadowsk wrote:On the AEM-7, at least pre rebuild, you could unbus the pans for sleet scrapping, to limit arcing at the front.

Historically, RRs operated with the rear pan up. This doesn't apply with newer EMUs, or on a lot of stuff in Europe where there's only one pan per loco for a given system - multisystem locos can have as many as 4 different pans on them.

I'm pretty sure the pantograph operation is still the same on the AC's in the case that boths pans are raised one has to be de energized because it can cause severe damage to the locomotive, it's written in BIG LETTERS in the manual. According to the book both pans are normally used for sleet scrapping etc because it wouldn't make sense to use the front to collect the power and scrape when you can scrape with one and get a clean draw with the rear.

Just to add a different twist here...

The Chicago South Shore & South Bend Railroad sometimes ran their 800-class Little Joes with both pans up. The reason was so that they could draw enough power from the wire for a longer train. In later years, I was told this practice was eliminated as the older substations along the line couldn't handle that much power draw!

But, alas, the Little Joes and the 700-class electric locos have been gone 20+ years or so, and all freight has been dieselized since then.

Did the New Haven run with both pans up other than de-icing? And the GG1s? What about other heavy electric RRs of the past?

>>>I'm pretty sure the pantograph operation is still the same on the AC's in the case that boths pans are raised one has to be de energized because it can cause severe damage to the locomotive, it's written in BIG LETTERS in the manual. <<<

I don't see how this could be the case if both pans are connected together electrically. Unless an unusual situation where the locomotive bridged a live to a dead section of catenary, such as a section where a breaker tripped because of a short, thus drawing excessive power and overloading the locomotive's internal power bus. Only reason I can think of. But even then, I would think that the locomtive itself would have a breaker to protect itself from damage.

SEPTA operates their AEM-7's and ALP44-hauled trains with the FRONT pan up for the direction of travel at all times. This has been the practice for almost 8 or 9 years now, and is required by SEPTA employee timetable special instructions.

Why, I have no idea, and nobody I know working over at the Railroad Division knows either...