Apt

[Lampshade]

The Pendolino's Pans are on opposite ends, or am I missing something?

It has a 25kV bus line running along the train so only one pan needs to be up though, the APT didn't have that as it was deemed a safety hazard back then.

 

[Eng274]

The Pendolino's Pans are on opposite ends, or am I missing something?

Only one is ever used at any given time, possibly direction dependent?

Re the power bus, I'm sure the juice is stepped down to a much lower voltage (about 1000-1500V) before being carried through the train. Is this what the curly flexes between Pendolino coaches are?

 

[ainsworth74]

Only one is ever used at any given time, possibly direction dependent?

It doesn't have to depend on direction (as in both pans can work both ways) but it is standard practice to use the pan furthest away from the front of the train (so a Euston bound 390 would use the pan at the Scottish end) as this gives the driver a bit more time to drop the pan if they see an obstruction in the OHLE (at least I think that's the reason).

Re the power bus, the juice is stepped down to a much lower voltage (about 1000-1500V) before being carried through the train. Is this what the curly flexes between Pendolino coaches are?

Didn't know it got stepped down, but I suppose thinking about it that it makes sense as 25kV carries quite a punch. Yes that's what the flex is between vehicles.

 

[Wyvern]

'Ang on. Slow down a minute.

The development process for the APT was not slow. It was a complete design from first principles, not an adaptation of existing technology (which had always been to a large extent "Try it and see").

The APT-E had power cars at each end and by the time the APT-P was on the stocks, experience had been gained with the HST, so I dont know the full details of the thinking about propelling - ie having the power car in the centre.

It is true that the use of only one power car and pantograph was because of contact problems at speed.

They couldn't use a bus down the train. I'm pretty certain there were Home Office regulations - which, in fact, had to be rescinded in order to introduce the Pendolino.

The design features of the APT informed the HST development, not the other way around, at least as regards the wheels and suspension.

The water brake was in addition to conventional brakes and it was the conventional brakes that gave trouble. But in the end no train could exceed 125 with the signalling system as it was.

 

[Lampshade]

It doesn't have to depend on direction (as in both pans can work both ways) but it is standard practice to use the pan furthest away from the front of the train (so a Euston bound 390 would use the pan at the Scottish end) as this gives the driver a bit more time to drop the pan if they see an obstruction in the OHLE (at least I think that's the reason).

The most logical explanation I can think of is if the rear pan is damaged through an obstruction on the OHLE, the front one has already cleared it so the train should be able to continue.

 

[Eng274]

It doesn't have to depend on direction (as in both pans can work both ways) but it is standard practice to use the pan furthest away from the front of the train (so a Euston bound 390 would use the pan at the Scottish end) as this gives the driver a bit more time to drop the pan if they see an obstruction in the OHLE (at least I think that's the reason).



Didn't know it got stepped down, but I suppose thinking about it it makes sense. Yes that's what the flex is between vehicles.

The more I think about it, and having done some National Grid substation structural design work, the inter-carriage cables are far too small for 25kV, you'd be looking at 30mm diameter heavy duty insulated cable, not too dissimilar from the thick beasts that droop between Voyager coaches.

It would be lighter, cheaper and easier to maintain to have one main transformer to step the voltage down than have one per carriage. And having unadulterated 25kV/3000A would necessitate a seriously sturdy traction motor!

Edit:....not to mention 5-point seat belts fitted as standard for when the driver as much as looks at the power handle.

 

[ainsworth74]

The most logical explanation I can think of is if the rear pan is damaged through an obstruction on the OHLE, the front one has already cleared it so the train should be able to continue.

Yeah that also makes sense as well actually. We do have a 390 driver on here so perhaps they could enlighten us as to the definitive reason.

And having unadulterated 25kV/3000A would necessitate a seriously sturdy traction motor!

Probably wouldn't be much room for anything else (like oh I don't know passengers) if your traction motor was designed to take that sort voltage/current Especially those amps, 3000 that's a lot of amps hock:

 

[ChrisCooper]

Only one is ever used at any given time, possibly direction dependent?

Re the power bus, I'm sure the juice is stepped down to a much lower voltage (about 1000-1500V) before being carried through the train. Is this what the curly flexes between Pendolino coaches are?

The power is stepped down by the transformer to around that voltage before being distributed to each motor coach, the same as happens on all other AC EMUs with distributed power (as opposed to having transformer and motors in one coach). The thing is though a single transformer small enough to fit under the floor is limited in how much power it can handle, so long and powerful trains like the Pendolino and the 395 have two transformers, one under each pantograph coach, supplying half the motor coaches each. The 25kV bus on the roof is what transfers 25kV from the active pantograph to the remote transformer. APTs also had one, but only linking the two adjacent powercars.
--- old post above --- --- new post below ---

The more I think about it, and having done some National Grid substation structural design work, the inter-carriage cables are far too small for 25kV, you'd be looking at 30mm diameter heavy duty insulated cable, not too dissimilar from the thick beasts that droop between Voyager coaches.

It would be lighter, cheaper and easier to maintain to have one main transformer to step the voltage down than have one per carriage. And having unadulterated 25kV/3000A would necessitate a seriously sturdy traction motor!

Edit:....not to mention 5-point seat belts fitted as standard for when the driver as much as looks at the power handle.

Cable size isn't voltage, it's current. Think how thin the 240v cables in a house are compared to the 12v cables coming off a car battery. Most cables in the house are 13A maximum though, wheras battery cables need to take a few hundered amps when starting. The thickest cables on a pendolino will be the low voltage cables between the transformer coaches and the motor coaches. These same cables are found on most other EMUs (or linking up all the shoe gear on third rail EMUs). They have always been allowed, except for use in certain tunnels (London Underground, Northern City line to Moorgate and the Merseyrail Tunnels under Liverpool), in which case each vehicle has it's own shoes and motors.

 

[507 001]

The power is stepped down by the transformer to around that voltage before being distributed to each motor coach, the same as happens on all other AC EMUs with distributed power (as opposed to having transformer and motors in one coach). The thing is though a single transformer small enough to fit under the floor is limited in how much power it can handle, so long and powerful trains like the Pendolino and the 395 have two transformers, one under each pantograph coach, supplying half the motor coaches each. The 25kV bus on the roof is what transfers 25kV from the active pantograph to the remote transformer. APTs also had one, but only linking the two adjacent powercars.
--- old post above --- --- new post below ---


Cable size isn't voltage, it's current. Think how thin the 240v cables in a house are compared to the 12v cables coming off a car battery. Most cables in the house are 13A maximum though, wheras battery cables need to take a few hundered amps when starting. The thickest cables on a pendolino will be the low voltage cables between the transformer coaches and the motor coaches. These same cables are found on most other EMUs (or linking up all the shoe gear on third rail EMUs). They have always been allowed, except for use in certain tunnels (London Underground, Northern City line to Moorgate and the Merseyrail Tunnels under Liverpool), in which case each vehicle has it's own shoes and motors.

But Merseyrail stock has a BUS line fitted? As well as shoe gear on both DMS cars.

 

[ChrisCooper]

But Merseyrail stock has a BUS line fitted? As well as shoe gear on both DMS cars.

Does it? I though because they ran in tube tunnels they couldn't. How many shoes do they have per DMS, 1 pair on the outer bogies or 2 pairs, one on each bogie?

The 313s on the Northern City line to Moorgate definitly don't have a bus line due to the tunnel (actually they do, to supply 750v from the transformer on the PTSO to the DMSs when on AC, but it's switched out when on DC so the motor coaches are electrically seperate). London Underground stock doesn't either.

 

[w1bbl3]

But in the end no train could exceed 125 with the signalling system as it was.

Interestingly enough the APT programme included development of a in cab signalling system based on track markers (balises) at 1km intervals, sadly the system was cancelled along with the APT programme.

 

[jrhilton]

They couldn't use a bus down the train. I'm pretty certain there were Home Office regulations - which, in fact, had to be rescinded in order to introduce the Pendolino.

What about the Class 373 on 25kv in North Pole depot from 1993 onwards, or when 373s were used/tested by GNER starting around April 2000, surely any rule would have been removed by then?

 

[ainsworth74]

What about the Class 373 on 25kv in North Pole depot from 1993 onwards, or when 373s were used/tested by GNER starting around April 2000, surely any rule would have been removed by then?

But the 373s have a locomotive at each end so there would be no need for a bus that runs through the train as each locomotive runs with its pantograph raised.

 

[jopsuk]

TGV sets typically operate with just the one pantograph (typically rear) raised, using a roof bus line*. The reason Eurostar won't have had this is presumably down to the (never used, soon to be no longer required as I understand it) ability to split the train- whilst it would surely be possible to have a safely splittable connector, if possibly to not have one then all the better given it would have been an emergency feature.

*no busline through the coupler, so multiple sets each have a pantograph raised

 

[swt_passenger]

The more I think about it, and having done some National Grid substation structural design work, the inter-carriage cables are far too small for 25kV, you'd be looking at 30mm diameter heavy duty insulated cable, not too dissimilar from the thick beasts that droop between Voyager coaches.

It would be lighter, cheaper and easier to maintain to have one main transformer to step the voltage down than have one per carriage. And having unadulterated 25kV/3000A would necessitate a seriously sturdy traction motor!

There's a useful 9 car Pendolino block diagram on page 15 of this:

http://www.networkrail.co.uk/browse... 2010/vt-ec4t-390 technical file issue 1b.pdf

As suggested earlier it doesn't work the way you think it does. Besides, you seem to be assuming it's a 75 MW train...

Edit: I see the report suggests max power is capped at 6 MW...

 

[Eng274]

There's a useful 9 car Pendolino block diagram on page 15 of this:

http://www.networkrail.co.uk/browse... 2010/vt-ec4t-390 technical file issue 1b.pdf

As suggested earlier it doesn't work the way you think it does. Besides, you seem to be assuming it's a 75 MW train...

I know it isn't a 75MW train! At no point did I actually say it was, though you've done the simple calculation and assumed I did. It followed on from this post by Ainsworth74

Didn't know it got stepped down, but I suppose thinking about it that it makes sense as 25kV carries quite a punch.

...as an explanation that if it wasn't stepped down, it would need stupidly high-spec, beefy traction motors. I am perfectly aware that the transformer(s) reduces the voltage to a point where its a more sensible 5-6MW output for the whole train.

 

[swt_passenger]

I know it isn't a 75MW train! At no point did I actually say it was, though you've done the simple calculation and assumed I did. It followed on from this post by Ainsworth74

My main point was to show that it does have a 25kV bus.

Your use of 25kV / 3000A was confusing, as was your 'singular' traction motor...

 

[Eng274]

My main point was to show that it does have a 25kV bus.

Your use of 25kV / 3000A was confusing, as was your 'singular' traction motor...

Which it does, as the pdf you linked to shows. On the roof I can see that not being an issue.

The 'singular' traction motor was (unclearly) intended to mean a design of traction motor to handle 25kV, etc etc. I also know that there are several traction motors on a 390, fairly obvious concept if distributed traction is to be achieved.

 

[ACE1888]

My middle name is Philip, my initials are therefore APT, just thought you'd all like to know that ....

 

[Wyvern]

That's very apt.

 

[Peter Sarf]

Regarding electricity cables (for that is what the bus line is). The higher the voltage then the lower the current required for the SAME power. If you double the voltage then you can half the current. What this means in terms of cable thickness is that if you increase the voltage you can reduce the thickness of the conductor because the current is less. BUT then there is the insulation which has to be better for a higher voltage. One way of improving electrical insulation is to make it thicker.

In the case of the national grid very very high voltages are used as this needs less metal for the conductor. The vast amount of insulation required is achieved with air - in other words the vast space between each conductor high up out of reach !. In railway terms 25KV AC is the highest voltage used for power and it would not work as third rail as you need to keep people about one metre away from it !!. That is why it is up there out of the way !!. In the case of the BUS line good insulation (instead of a large air gap) is needed as the conductor is part of the train.

Hope the above explanation helps - if so then you can say I have an aptitude for this (sorry).

 

[vectra33]

The pendolinos can use either pan.
When they were first introduced the front one was always used,the rear one being in the down position.
About 18 months ago this rule was reversed,and now the rear one is always used.

The logic behind this is if the wires are brought down,damage will only be caused to the rear few coaches,rather than the whole length of the train.

Apparently this is the recommendation of the makers,but when the pendo was introduced,the marketing people at virgin felt the train would somehow look better and safer if the front pan was seen to be raised when travelling.

Dave

 

[TomJ93]

The Coventry railway centre is borrowing the APT-E I hear.