Pantograph

[Scotrail88]

Not sure if this would be possible but in Scotland (not sure if common elsewhere) a multiple EMU has both its Pantographs up when joined.

Could the train not operate with only 1 pantograph when in multiple formation and therefore reduce wear on the train as well as on the overheads?

Surely this would save cost and time for replacements if possible.

 

[swt_passenger]

Not sure if this would be possible but in Scotland (not sure if common elsewhere) a multiple EMU has both its Pantographs up when joined.

Could the train not operate with only 1 pantograph when in multiple formation and therefore reduce wear on the train as well as on the overheads?

Surely this would save cost and time for replacements if possible.

There is no 25 kV link between EMUs running together in multiple, so that’s a definite “not possible”. The insulation requirements for such a high voltage rule out passing it through any sort of electrical box on a coupling.

Long fixed formation trains such as the 8 or 12 car Thameslink Class 700s are made up of two permanently coupled half trains and normally run with both pans up.

Other long fixed formation trains such as the Pendolino or IET use a different setup and have a 25 kV bus line along the roof, and only use 1 of their two pantographs.

 

[hexagon789]

Not sure if this would be possible but in Scotland (not sure if common elsewhere) a multiple EMU has both its Pantographs up when joined.

Could the train not operate with only 1 pantograph when in multiple formation and therefore reduce wear on the train as well as on the overheads?

Surely this would save cost and time for replacements if possible.

I believe that most (possibly all), UK overhead Electric Multiple Units have one pan up per unit when operating multiple sets together. On the continent I believe there are some trains which have a 25kV bus-line such as French TGVs where only the rear pantograph is up when operating on 25kV and the power is transmitted via a cable on the roof to the front power car.

BR didn't like this arrangement with passenger vehicles, I forget why, which is why the APT-P had the two power cars next to each other.

 

[swt_passenger]

BR didn't like this arrangement with passenger vehicles, I forget why, which is why the APT-P had the two power cars next to each other.

Whatever BR thought at the time of the APT has been overtaken by more recent decisions though...

 

[nat67]

Whatever BR thought at the time of the ATP has been overtaken by more recent decisions though...

ATP (Automatic Train Protection)?

 

[causton]

Sometimes due to a train fault a train will "cross-couple" where another train will mechanically couple and in essence tow the "dead" train back. I believe only one pantograph would be up on this, on the "good" train?

 

[Mag_seven]

ATP (Automatic Train Protection)?

I think they mean APT (Advanced Passenger Train)?

 

[swt_passenger]

Sometimes due to a train fault a train will "cross-couple" where another train will mechanically couple and in essence tow the "dead" train back. I believe only one pantograph would be up on this, on the "good" train?

Yes, but only one unit would be powered up.

 

[hexagon789]

Whatever BR thought at the time of the APT has been overtaken by more recent decisions though...

Are there any UK EMUs with 25kV bus lines these days then?

 

[swt_passenger]

Are there any UK EMUs with 25kV bus lines these days then?

Yes, Pendolino and IET, as I mentioned in my earlier reply.

 

[edwin_m]

There is no problem with a 25kV bus line. The problem is devising one that can safely be coupled and uncoupled between units that are separated in service.

 

[hexagon789]

Yes, Pendolino and IET, as I mentioned in my earlier reply.

Do two IETs in multiple run with only one pan up then?

 

[JN114]

Do two IETs in multiple run with only one pan up then?

No, each unit has its Pan up.

 

[driver9000]

Yes, but only one unit would be powered up.

How do you define powered up? When hauling a dead 350 the assisting 350 can supply 110v to provide lighting, ventilation and control but not traction power.

 

[ComUtoR]

Long fixed formation trains such as the 8 or 12 car Thameslink Class 700s are made up of two permanently coupled half trains and normally run with both pans up.

700's can run with a single pan.

 

[hexagon789]

No, each unit has its Pan up.

Which is what I meant, it has to have a pantograph on each unit must be raised. One pantograph doesn't supply power to both unit.

 

[swt_passenger]

700's can run with a single pan.

So they can, but then half the unit is pulling the dead half, because they are two independent half trains...

 

[swt_passenger]

How do you define powered up? When hauling a dead 350 the assisting 350 can supply 110v to provide lighting, ventilation and control but not traction power.

In the current context I'd be using "powered up" to refer to traction power...

 

[K.o.R]

There is no 25 kV link between EMUs running together in multiple, so that’s a definite “not possible”. The insulation requirements for such a high voltage rule out passing it through any sort of electrical box on a coupling.

I'm imagining one of those giant power relay bars you see in substations dropping to make contact between the units, with the impressive light show when it comes time to uncouple.

 

[supervc-10]

I don't think it would be impossible to engineer a new design of coupling electrical box including a 25kV connector, but I think it would be pointless. All it would serve is to enable one unit in the pair to run pan down, which isn't exactly a huge benefit.

The 700s are effectively 2 units, each with only one cab, running coupled together aren't they? From an electrical point of view that is.

 

[swt_passenger]

I don't think it would be impossible to engineer a new design of coupling electrical box including a 25kV connector, but I think it would be pointless. All it would serve is to enable one unit in the pair to run pan down, which isn't exactly a huge benefit.

The 700s are effectively 2 units, each with only one cab, running coupled together aren't they? From an electrical point of view that is.

Yes, as I explained in the first reply in this thread.

 

[37057]

I don't think it would be impossible to engineer a new design of coupling electrical box including a 25kV connector, but I think it would be pointless. All it would serve is to enable one unit in the pair to run pan down, which isn't exactly a huge benefit.

Stray 110v in the couplers during wet weather can be bad enough.

 

[Sleeperwaking]

I don't think it would be impossible to engineer a new design of coupling electrical box including a 25kV connector, but I think it would be pointless. All it would serve is to enable one unit in the pair to run pan down, which isn't exactly a huge benefit.

Running with multiple pantographs raised has impact on the pan / OLE interaction for the trailing pantograph, particularly if the distance between each pantograph is quite short. A lot of the work to support increasing the Class 350 line speed from 100 mph to 110 mph in 3 unit formations was around the pan forces with three pantographs raised. Essentially, the trailing pan contact forces will have a much higher variance, which can result in excessively high forces and excessively low forces / loss of contact. Both can increase the wear on the contact wire, particularly if you have loss of contact resulting in arcing, and I presume high forces can affect other OLE components as well.

As mentioned above, there is not yet a robust solution for couplers / jumpers that can pass either 25 kV or traction current between separate units - until then, you need at least one pantograph raised per unit to power the traction systems.

 

[supervc-10]

Stray 110v in the couplers during wet weather can be bad enough.

I'm thinking things can be disconnected while the actual coupling is taking place, with power only being sent across the connection when everything is confirmed as safe.

I'm not saying it's practical or cheap, I'm just saying that I don't think that it's impossible.