-
Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!
how long to switch power supply on a bi-mode?
- Thread starter TheWalrus
- Start date
- Status
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R
RailUK Forums
TGV
Member
I presume the two modes in question are diesel power to 25kV?
I've not had time to prepare an answer, but if I may scribble some thoughts down:
For seamless changovers, I'd separate traction and aux (hotel) power. So the changeover could be something like:
1 - Train comes to a stop under diesel power.
2 - Traction systems isolated from alternator and any appropriate system earthing done.
3 - Pantograph raised, VCB closed when voltage detected as correct
4 - Transformer energised to activate traction systems
5 - At this point the diesel engine is still powering aux systems
6 - Then swap aux systems to overhead line supply
7 - Kill the diesel once confirmation of changeover.
As I said it's just off the top of my head, but in reality this could be done in less than 2 minutes with modern equipment. Maybe even less.
I've not had time to prepare an answer, but if I may scribble some thoughts down:
For seamless changovers, I'd separate traction and aux (hotel) power. So the changeover could be something like:
1 - Train comes to a stop under diesel power.
2 - Traction systems isolated from alternator and any appropriate system earthing done.
3 - Pantograph raised, VCB closed when voltage detected as correct
4 - Transformer energised to activate traction systems
5 - At this point the diesel engine is still powering aux systems
6 - Then swap aux systems to overhead line supply
7 - Kill the diesel once confirmation of changeover.
As I said it's just off the top of my head, but in reality this could be done in less than 2 minutes with modern equipment. Maybe even less.
To be fair, the twelve minutes includes braking from 110mph to zero for a station stop then getting back to 110mph from a different power source. Nobody said it takes twelve minutes to switch from electric to diesel and vice-versa.
asylumxl
Established Member
I don't actually remember the line speed at Bedford, but I'm pretty sure it's not 110mph...
Fair enough - I asked what the line speed was in the thread and was told 110 so that is all I had to go on.
The point stands though, it was not suggested it took 12 minutes from arriving in to departing a station - it included braking to a stand from line speed and getting back up to line speed again.
Surely if the 313s can switch from overhead to 3rd rail and back in a matter of seconds, then the electric-diesel switchover shouldn't take much longer? I know they have to start the diesel engine up and so forth, but even then surely it won't be all that long?
Of course, Voyagers and other long distance trains do have quite a bit of dwell time in major stations, so I doubt it would realistically make journeys in longer.
Of course, Voyagers and other long distance trains do have quite a bit of dwell time in major stations, so I doubt it would realistically make journeys in longer.
asylumxl
Established Member
There isn't. People making assumptions that Bombardier will use something similar to the management system on the Electrostars, which have to stop.
I don't think people were making assumptions, they were just commenting on what happens on some stock now.
Like you say, there is no reason why it can not be done. But there is no reason why it can't be done on Electrostars either if they had been specced properly.
TGV - thanks, that's the ideal answer I wanted! 
ukrob - I apologise for my misinterpretation of what was said. I didn't realise this actually included getting back to line speed and all. I meant the just the changeover bit after the train had stopped, but before it restarts.
ukrob - I apologise for my misinterpretation of what was said. I didn't realise this actually included getting back to line speed and all. I meant the just the changeover bit after the train had stopped, but before it restarts.
asylumxl
Established Member
And what current bi-mode (D/EMU) stock are the comments being drawn from?
cyclebytrain
Member
- Joined
- 11 Jul 2009
- Messages
- 311
Why not start from the worst case scenario? How long does it take from engine start from cold on a 22x -it won't be more than that...
O L Leigh
Established Member
I say this so often that it's almost become a catchphrase. You can't raise a pan on the move because you risk damaging the pan and/or the OLE, and possibly causing a dewirement.
O L Leigh
TGV
Member
Class 373 has been doing it for years at up to 100mph. It has never caused a de-wirement and the pan-heads cope fine.
None in the UK for sure.
I apologise for a discussion taking place on a discussion forum. We will stick to facts from now on with theories and opinions no longer allowed :roll:.
You really seem to have a problem with discussion?
--- old post above --- --- new post below ---
True, but not on conventional (cheap) British OHL they haven't though.
Last edited:
O L Leigh
Established Member
asylumxl
Established Member
Nope, no problem with discussion. I just don't see how we can really quote numbers we don't have evidence to back up, that's all.
So like I said, you want facts or nothing at all - so I guess we can't talk about the project until is officially announced that 22X will have a pantograph coach inserted and the specs are released - because only then will there be any 'evidence'.
O L Leigh
Established Member
The simple answer is that, as there are no bi-mode trains, it is impossible to say how long a traction changeover would take and whether 7-12 minutes is a reasonable estimate or not. Such matters will be down to the design of the train itself and the operation of the train management system. At the present moment we're all just plucking numbers out of the air with nothing to base it on.
O L Leigh
asylumxl
Established Member
You can talk about whatever you like. I don't want to drag the thread any further off topic. I just don't get where people are even getting these numbers, that's all.
Thank you!
Kingfisher200262
Member
China has the pantograph technology to raise and lower the pan at speed, even on dodgy infrastructure. After that, it's simply a matter of what you do with the juice and how you manage / control it. Putting the pan up, does not necessarily mean that you draw power immediately and a smooth changeover can be effected, with a small gap, where there is no energy being supplied to the traction system, in the same way as happens when an electric train passes through a neutral section, which passengers never notice.
I have been accused on here of unreasonably promoting our own products, so I won't explain how this issue will be dealt with on our own bi-mode product, unless the concensus agrees that I should.
TGV
Member
Nope - it does it on the 3kV classic-line OLE in Belgium which if you've seen it, is every bit as "cheap" (if that's the phrase we're using) as ours. In fact the tension in theirs is LESS than ours - you should see how it responds when a train passes - lazily bouncing up and down. Makes the ECML wires look like a guitar string.
--- old post above --- --- new post below ---
While there's an element of truth in that - my breakdown of the steps involved wasn't plucked from the air. I was giving a more thorough explanation based on experience of working with rolling stock that changes power supply.
--- old post above --- --- new post below ---
So do we... see above.
route:oxford
Established Member
- Joined
- 1 Nov 2008
- Messages
- 4,949
So...
When a 73 arrives at the final station with 3rd rail on a "normal" diagram, how long does it take to retract the shoe(???) and progress on Diesel?
Likewise when it arrives at the first station with 3rd rail after running on Diesel, how long does it take before it can progress on electricity.
When a 73 arrives at the final station with 3rd rail on a "normal" diagram, how long does it take to retract the shoe(???) and progress on Diesel?
Likewise when it arrives at the first station with 3rd rail after running on Diesel, how long does it take before it can progress on electricity.
Kingfisher200262
Member
Good... so I don't see what everybody's getting so worked up about then. Changeover at line speed, without 8.... or 12 minutes delay!
It won't take long to switch power supplies.
Loco's/EMU's go over neutral sections without anyone noticing that they are running on batteries. It is at similar points the unit could switch its supply.
As for the warming up of diesel engines, they could start them at whatever the minimum heat up time is whilst the unit is running on OHL/3rd rail.
I think the main question is what weight is a main transformer compared to a diesel engine/exhaust system etc and its fuel?
Loco's/EMU's go over neutral sections without anyone noticing that they are running on batteries. It is at similar points the unit could switch its supply.
As for the warming up of diesel engines, they could start them at whatever the minimum heat up time is whilst the unit is running on OHL/3rd rail.
I think the main question is what weight is a main transformer compared to a diesel engine/exhaust system etc and its fuel?
TGV
Member
It could (and trains do) change power supplies at speed, but in the case of diesel to electric, while it IS possible, I'm expecting most changeovers of this type to be done while stationary.
The reason being that overhead lines rarely just stop in the middle of the countryside. They normally run to a destination that is significant on that route. Significant enough to have been "wired" up to in the first place. If the train is travelling on that route, it's likely it'll be stopping at such a station anyway.
For example, lets suppose a bi-mode train is travelling from Stranraer to Glasgow via Ayr (the sensible route). The line is non-electrified to Ayr where the wires start. The train will run diesel until it stops at Ayr, then while it's already stationary waiting for passengers to board/alight, the changeover will happen and it'll carry on North under 25kV. The point is that on such a diagram, the train would stop at Ayr because it's the main intermediate station on the route.
Same applies if travelling north out of Edinburgh. The changeover would likely happen at either Waverley or Haymarket, not randomly in the countryside.
If you were to read the posts, you would see that the time included linespeed to zero for a station and backup to linespeed. It seems most people are overlooking that fact because it suits them.
Kingfisher200262
Member
I did read all the posts. The reason I chose to ignore the time to slow down, stop and the time to get back up to line speed is because if you're stopping at a station in any case, this time exists whether you're changing mode or not!
It seems to me that the only timing penalty issue here is whether you need to wait for engines to warm up or not, which you should not need to do if the train is designed properly!!
The bigger issue is whether this is a good idea at all (bi-mode that is) and that really depends upon the application. In my opinion, the routes where bi-mode might be logical are where you wish to run direct trains to destinations where the majority of the route is electrified, but electrification of a small part of the route cannot be justified. Routes where this MIGHT apply (I'm not going to get into a debate about whether or not to electrify this or that route) are: -
London - Sunderland
London - Bradford
London - Hull
London - Plymouth - Penzance (assuming GWML electrification to Exeter)
London - Blackpool
London - Holyhead
London - Swansea (assuming GWML electrification to Bristol - sharp intake of breath!)
London - Great Yarmouth
London - Derby (MML)
This list is not exhaustive.
can French bi-mode AGC classes B81500 and B82500 change on the move? If not, how long do they spend changing at stations?
What about the electro-diesels in the US? these operate mainly around the New York area- do they stop to change or change on the move? Admittedly, they're 3rd rail power.
We talk about bi-mode as if it is some mystical future technology. It isn't. It is here, it is now. Even better, it is Bombardier (builders of the 22x classes) who build the French units.
What about the electro-diesels in the US? these operate mainly around the New York area- do they stop to change or change on the move? Admittedly, they're 3rd rail power.
We talk about bi-mode as if it is some mystical future technology. It isn't. It is here, it is now. Even better, it is Bombardier (builders of the 22x classes) who build the French units.
- Status