Are both Acela II power cars active at the same time?

[aegrotatio]

Are both Acela II power cars active at the same time?

If so, how is power transmitted from the power car with the active pantograph to the trailing power car with the lowered pantograph?

[MidlandMike]

Could it be that the pantograph only rises when extra power is needed from the rear unit?

[CSSHEGEWISCH]

All of the photos that I've seen show the pantograph raised on both power cars.  A high-voltage bus line would be needed to supply electricity to both power cars from one pantograph.

[CMStPnP]

MidlandMike

Could it be that the pantograph only rises when extra power is needed from the rear unit?

Or possibly the rear one is for regenerative braking and returning electricity back to the wire?   Can you both draw and supply electricity via one pantograph?  

[aegrotatio]

CSSHEGEWISCH

All of the photos that I've seen show the pantograph raised on both power cars.  A high-voltage bus line would be needed to supply electricity to both power cars from one pantograph.

 

Testing at Pueblo and in New Jersey show only one pantograph raised in the videos I've seen.

 

[Overmod]

CMStPnP

Can you both draw and supply electricity via one pantograph?

On single-phase AC you can, provided that you're synthesizing the frequency and waveform, and your inverter setup can adjust the power factor correctly.  Synchronization, which used to be a big issue, is trivial now, because the inverter can measure the frequency and waveform of the AC in the catenary and sync to it as a reference; this is something that non-islanded distributed generation does all the time...

The flow of current is continuous through the pantograph from full acceleration all the way to full regenerative braking.  There may be a 'null point' where regenerated power just equals demanded power (you could guess this would be at 0 amps either way over a couple of cycles) or you get current alternation at some trivial number of coul. at line frequency until the regeneration or throttle ramp up.  But there is no reason why one can't do for each.

One of the reasons FRA was reluctant to grant waivers to TGV equipment was that the early types used 25kV underfloor cabling, which gives some people the willies (and perhaps ought to do so for more, but I'm not one of them... yet).  The specific example of Reading-type inter-unit bus bars over the roofs has been raised ... and rejected ... for higher-voltage equipment at the necessary high horsepower and current needed for HSR (a typical TGV, I believe, is now over 25,000hp at top speed).

I should know if top-and-tail operation with both pans up was ever contemplated for this set.  What I do know is that only one pan can be up for sustained high speed (higher than these sets will likely ever reach in their service lifetimes, but we can dream) because the complex waves induced in the catenary are not damped (either in fixed or constant-tension cat) until well beyond that second pantograph's location.  So I suspect the underfloor arrangement...

[charlie hebdo]

Overmod

One of the reasons FRA was reluctant to grant waivers to TGV equipment was that the early types used 25kV underfloor cabling, which gives some people the willies (and perhaps ought to do so for more, but I'm not one of them... yet)... higher-voltage equipment at the necessary high horsepower and current needed for HSR (a typical TGV, I believe, is now over 25,000hp at top speed).

Have there been any electrocutions from underfloor high voltage wiring on the 39 years of heavy TGV usage?  I think not.  However,  at least one rail surfer was electrocuted on the roof. 

[Overmod]

charlie hebdo

Have there been any electrocutions from underfloor high voltage wiring on the 39 years of heavy TGV usage?  I think not.

But this is the same FRA that refused to give a waiver on a buff test that failed something like 8K short of an exaggerated statutory 850K.  Like the EPA that refused a waiver for EMD on a 0.3% (that is not a typo) failure to make arbitrary Tier 4 final NOx over a small part of the test duty cycle.  Science or sense can be in short supply when politics, especially expedient politics masquerading as technical regulation, is in play.

I confess that the way things are in this country now, if Acelas can separate at high speed and Talgos derail at high speed on known curves, I can imagine scenarii in which something goes wrong with a 25kV sealed cable to allow potential to reach 'passenger contact'.  Might be as little as a few volts at negligible current, but if that happens to derange a pacemaker... there you go.  Certainly the chance of inadvertent contact with Reading-style overhead bus-bar plates is higher, and I wouldn't argue otherwise; I notice that the approach is not used on any subsequent NJT or SEPTA MU equipment despite Reading having used it many years without any lethal effect I heard about.

And no, the French won't have that problem.  Even on trainsets now in 'ouigo' bargain service.  

However,  at least one rail surfer was electrocuted on the roof.

Leaving aside situations like the YouTube video in India, which shows the prompt lethality of 1500 to 3000VDC conduction, we at Princeton had one of the more notorious nitwit test cases, a couple of inebriated people (I won't say who) that decided it would be great sport to put the pans up on a parked Silverliner sometime in the wee hours of the morning -- and climbed up the outside and started yanking on the lowered pan to get it to go up to the wire.  Surprisingly this resulted only in severe flash burns -- most of the current path at even 11kV going around the core of the body -- which is how the cream of the details became so well known.  Most of the concern I've had expressed over 25kV or 50kV cabling is the long-term integrity of the whole of the insulation under potential maintenance neglect -- and referring back to the Acela incident: if that could happen, damaging separation to a high-voltage intertie might, too ... and I couldn't predict what the current might ground to before the substation protection activated.  (It was common practice on the 11kV to 12.5kV ex-PRR south of NYC to cycle the breaker a couple of times when a fault occurred, just in case it was transient ... this is the same kind of practice that killed so many in the Malbone Street wreck.)

My opinion in 'actuality' is the same as yours: there's little objective point in concern over even 50kV underfloor if you have good design and appropriate long-term maintenance policies and oversight in force.  And keeping the cable inside additional structure, preferably armored and isolated, makes better sense than carrying it on the roof where a variety of damage becomes less unlikely.

[charlie hebdo]

The proof is in the pudding.   Nearly 40 years of heavy usage, heaven knows how many km run and passengers carried.  But Amtrak maintenance might not be up to SNCF standards