German proposal of Induction power as OLE alternative

[squizzler]

The DLR (German aerospace laboratory, presumably their equivalent of the former Royal Aircraft Establishment at Farnborough) is working on a concept for future trains called NGT (Next Generation Train). Three types are envisioned from the basic concept - ultra-high-speed (HST), regional (LINK) and goods (CARGO). This research has been going on a number of years and produced a concept for a UK gauge double deck train a couple of years back.

From the HST variant, an inductive power supply is proposed within the track. From the page:

The energy supply for NGT HST is integrated into the track, eliminating the need for a maintenance-intensive catenary. The propulsion concept is based on inductive power transfer from the track to receivers distributed over the length of the train. The pantograph is normally a significant source of wear and noise, and this system renders it unnecessary.

My speculation: The cited distribution of receivers along the length of the train suggests to me that each one can only collect limited current and several are required to transfer the necessary power. So a locomotive could not receive enough power by itself to haul a train. The concept is for a 400kph HST, and I also wonder if the forward velocity plays a part in allowing the train to pull power from the track coils, similar to a how a ramjet only works at supersonic speeds.

Nonetheless, this might be an interesting technology in the context of the UK's constricted overhead clearances. It would be interesting to know how far development of this has come along.

There are a lot of speculative technologies on the NGT, which might bear discussion in dedicated thread(s) in the rolling stock category!

 

[NSEFAN]

The DLR (German aerospace laboratory, presumably their equivalent of the former Royal Aircraft Establishment at Farnborough) is working on a concept for future trains called NGT (Next Generation Train). Three types are envisioned from the basic concept - ultra-high-speed (HST), regional (LINK) and goods (CARGO). This research has been going on a number of years and produced a concept for a UK gauge double deck train a couple of years back.

From the HST variant, an inductive power supply is proposed within the track. From the page:



My speculation: The cited distribution of receivers along the length of the train suggests to me that each one can only collect limited current and several are required to transfer the necessary power. So a locomotive could not receive enough power by itself to haul a train. The concept is for a 400kph HST, and I also wonder if the forward velocity plays a part in allowing the train to pull power from the track coils, similar to a how a ramjet only works at supersonic speeds.

Nonetheless, this might be an interesting technology in the context of the UK's constricted overhead clearances. It would be interesting to know how far development of this has come along.

There are a lot of speculative technologies on the NGT, which might bear discussion in dedicated thread(s) in the rolling stock category!

One of the main reasons for using electric traction is the better efficiency. I would be very surprised if they can get inductive coupling to work efficiently, as it is much more lossy compared to a physical electrical contact. The only time you would use them is either for safety or restricted clearances, so they have a fair case for trams or maybe shunting yards, but I can't see them being widely used for very high power or high speed applications.

 

[AM9]

One of the main reasons for using electric traction is the better efficiency. I would be very surprised if they can get inductive coupling to work efficiently, as it is much more lossy compared to a physical electrical contact. The only time you would use them is either for safety or restricted clearances, so they have a fair case for trams or maybe shunting yards, but I can't see them being widely used for very high power or high speed applications.

And just imagine the EMC issues.

 

[deltic08]

The DLR (The concept is for a 400kph HST, and I also wonder if the forward velocity plays a part in allowing the train to pull power from the track coils, similar to a how a ramjet only works at supersonic speeds.

Ramjets wok at subsonic speeds too.

 

[squizzler]

The only time you would use them is either for safety or restricted clearances

Those are not the benefits suggested by DLR! I would be sceptical if induction current collection was suggested by a lay-person, but the pedigree of DLR requires us to take this proposal seriously. The price of such a system is not suggested - and probably outside the remit of pure research - so we don't know if it is cost effective on any other than the ultra high speed corridors.

And just imagine the EMC issues.

You have to immunise your signalling if you want to electrify anyway. Ironically, it might cause less interference as the frequency of the inductive pickup is likely different from 50hz which is the frequency of AC OLE and that of all other mains powered equipment - I understand harmonic frequencies are the dangerous ones. Anyway, perhaps the inductive coils can be used for train detection, so you would not have to immunise other train detection at all?

Ramjets wok at subsonic speeds too.

I thought it was supersonic shock waves that compress the air. Perhaps I am thinking of scramjets?

 

[NSEFAN]

Those are not the benefits suggested by DLR! I would be sceptical if induction current collection was suggested by a lay-person, but the pedigree of DLR requires us to take this proposal seriously. The price of such a system is not suggested - and probably outside the remit of pure research - so we don't know if it is cost effective on any other than the ultra high speed corridors.

I also do research on inductive power transfer systems, and the only good reasons for doing it at high power levels are either for safety (preventing the need for exposed HV cables) or operational convenience (I. E. putting up wires or plugging something in is too much hassle). On the issue of pantograph resistance, I would imagine that there's a tradeoff between energy lost due to this and energy lost in inductive power transfer, and also the ongoing maintenance costs for both systems. I am obviously not privy to the calculations, and the area is obviously worth investigating, but it does surprise me that high speed would be seriously considered for inductive powering.

It is much like the tradeoff in Maglev. You can get rid of the rolling resistance of wheels and bearings, but have to pay for extra energy to make it float. In that case you would only bother doing this to make it go very fast. The game may change if someone can make higher temperature superconductors commercially viable, but until then most trains (commuter, regional, classic intercity, freight) are better off using metal rails and flanged wheels.

 

[deltic08]

I thought it was supersonic shock waves that compress the air. Perhaps I am thinking of scramjets?

You are thinking along the right lines but it works at subsonic speeds too. The V1 doodle bug had no moving parts so relied on forward movement to compress the air once launched. They flew at about 400 mph. I think it was called a pulse jet.

 

[Pigeon]

A pulse jet is different again; it uses Kadenacy effect and (in some cases, including the V1) ram effect for scavenging, but there is next to no compression, which contributes to the abysmal fuel consumption. It is arguably even simpler than a ramjet - some designs there is no argument - but unlike a ramjet, it can start from stationary. So it was ideal for a one-shot disposable application like the V1 (sure that had an assisted launch, but that was needed to avoid the need for runways, not for getting the engine going.)

More to the point, though, is that electricity doesn't work like that; there is no effect analogous to, or even vaguely similar to, ram effect that might affect pickup (by whatever method) at high speed. Some odd things might happen at relativistic speeds but that hardly applies to railways!

I consider the "induction pickup" idea to be over-complex, over-lossy, and over-extravagant in materials; I am amazed it's even been suggested seriously - although given that the history of barmy traction ideas is nearly as long as that of railways in general, perhaps I shouldn't be. I certainly agree with the idea of getting rid of OLE, but that can be done much more simply with rail pickup, using a combination of a relatively modest increase in voltage and final distribution via large-section aluminium bus bars linked to the rails every few tens of metres instead of via the rails themselves, by which means the losses can be reduced to the same level as with 25kV overhead. And whatever method is used it would mean replacement of a massive amount of lineside equipment plus either new traction or major modification to existing traction, so I can't see it ever happening anyway.

I don't think that's the only dodgy idea either...

"Several EMUs can be virtually coupled together, thus increasing operational flexibility."

Good luck with that one, mate, they've been trying to do it with lorries on motorways for 20+ years and it still doesn't work... (Sure, that's not exactly the same problem, but the easier bits and the harder bits more or less cancel out.)

"This remote, contactless coupling functionality allows trains to rendezvous while travelling at cruising speed. With the introduction of flexible block distances as a principle of railway safety, this would enable a further increase in line capacity."

Yeah, I've had ideas like that, but even I'm not daft enough to seriously think they'd be a goer...

 

[deltic08]

A pulse jet is different again; it uses Kadenacy effect and (in some cases, including the V1) ram effect for scavenging, but there is next to no compression, which contributes to the abysmal fuel consumption. It is arguably even simpler than a ramjet - some designs there is no argument - but unlike a ramjet, it can start from stationary. So it was ideal for a one-shot disposable application like the V1 (sure that had an assisted launch, but that was needed to avoid the need for runways, not for getting the engine going.)

More to the point, though, is that electricity doesn't work like that; there is no effect analogous to, or even vaguely similar to, ram effect that might affect pickup (by whatever method) at high speed. Some odd things might happen at relativistic speeds but that hardly applies to railways!

I consider the "induction pickup" idea to be over-complex, over-lossy, and over-extravagant in materials; I am amazed it's even been suggested seriously - although given that the history of barmy traction ideas is nearly as long as that of railways in general, perhaps I shouldn't be. I certainly agree with the idea of getting rid of OLE, but that can be done much more simply with rail pickup, using a combination of a relatively modest increase in voltage and final distribution via large-section aluminium bus bars linked to the rails every few tens of metres instead of via the rails themselves, by which means the losses can be reduced to the same level as with 25kV overhead. And whatever method is used it would mean replacement of a massive amount of lineside equipment plus either new traction or major modification to existing traction, so I can't see it ever happening anyway.

I don't think that's the only dodgy idea either...

"Several EMUs can be virtually coupled together, thus increasing operational flexibility."

Good luck with that one, mate, they've been trying to do it with lorries on motorways for 20+ years and it still doesn't work... (Sure, that's not exactly the same problem, but the easier bits and the harder bits more or less cancel out.)

"This remote, contactless coupling functionality allows trains to rendezvous while travelling at cruising speed. With the introduction of flexible block distances as a principle of railway safety, this would enable a further increase in line capacity."

Yeah, I've had ideas like that, but even I'm not daft enough to seriously think they'd be a goer...

Thank you Pigeon for a full explanation but I think 25kv is here to stay.

 

[edwin_m]

I also wonder if the forward velocity plays a part in allowing the train to pull power from the track coils, similar to a how a ramjet only works at supersonic speeds.

More to the point, though, is that electricity doesn't work like that; there is no effect analogous to, or even vaguely similar to, ram effect that might affect pickup (by whatever method) at high speed. Some odd things might happen at relativistic speeds but that hardly applies to railways!

I think perhaps squizzler was thinking of the effect where induced currents can create magnetic levitation above a certain speed, without the need for external power to the levitation coils.

The repulsive and attractive force in the track is created by an induced magnetic field in wires or other conducting strips in the track. ... However, at slow speeds, the current induced in these coils and the resultant magnetic flux is not large enough to levitate the train. For this reason, the train must have wheels or some other form of landing gear to support the train until it reaches take-off speed. Since a train may stop at any location, due to equipment problems for instance, the entire track must be able to support both low- and high-speed operation.

https://en.wikipedia.org/wiki/Maglev#Electromagnetic_suspension_(EMS)

 

[squizzler]

More to the point, though, is that electricity doesn't work like that; there is no effect analogous to, or even vaguely similar to, ram effect that might affect pickup (by whatever method) at high speed. Some odd things might happen at relativistic speeds but that hardly applies to railways!

I think perhaps squizzler was thinking of the effect where induced currents can create magnetic levitation above a certain speed, without the need for external power to the levitation coils.

Thank you Edwin, you beat me to the punch when I was typing a response!

The ramjet was a flawed metaphor on my part. A better analogy is the Japanese maglev technology which uses electromagnets on the train that interact with coils on the track to lift the train. It relies on relative velocity between the two and only "takes off" when the train gets to nearly 100 mph.

In the case of high speed current collection, rather than inducing magnetic field with AC from the induction coil, perhaps DC can be used and an alternating magnetic field produced by movement of the train over alternate coils connected with reversed polarity?

 

[edwin_m]

In the case of high speed current collection, rather than inducing magnetic field with AC from the induction coil, perhaps DC can be used and an alternating magnetic field produced by movement of the train over alternate coils connected with reversed polarity?

That might work at high speeds but it leaves an even bigger problem than the maglev, in that the train doesn't have any power at all until it gets to that high speed! Also induction is less effective at lower frequencies.

In principle a series of electromagnets could be placed along the track and energised in sequence to pull the train along from one to the next. That's a bit like unwrapping the electric motor and laying it out along the track, and I suspect it would only work with a train that is non-magnetic except for one or more "propulsion lumps" placed in the appropriate positions underneath. My mother-in-law has just had a pacemaker so I must remind her not to travel on one of these...

 

[squizzler]

I don't think that's the only dodgy idea either...

"Several EMUs can be virtually coupled together, thus increasing operational flexibility."

Good luck with that one, mate, they've been trying to do it with lorries on motorways for 20+ years and it still doesn't work... (Sure, that's not exactly the same problem, but the easier bits and the harder bits more or less cancel out.)

"This remote, contactless coupling functionality allows trains to rendezvous while travelling at cruising speed. With the introduction of flexible block distances as a principle of railway safety, this would enable a further increase in line capacity."

Yeah, I've had ideas like that, but even I'm not daft enough to seriously think they'd be a goer...

These ideas might seem far fetched to us, but railway research is moving in that sort of direction. SNC Lavalin announced research on this kind of thing a couple of areas ago. In fact I think "dynamic coupling" was to be tested in the field, on a new Italian line, unless I am imagining it.

Whilst ETCS level 3 is not yet with us, it makes sense to be already looking at where it goes from there - hypothetical levels 4 and 5 - which opens the doors to all sorts of EMU kung-fu as described.

 

[Pigeon]

In the case of high speed current collection, rather than inducing magnetic field with AC from the induction coil, perhaps DC can be used and an alternating magnetic field produced by movement of the train over alternate coils connected with reversed polarity?

That makes a generator, with the mechanical input provided by whatever is pushing the train along. It doesn't transfer power from the track. If whatever is pushing the train along is a traction motor running off the generator output, then you have a perpetual motion machine; essentially a more complicated version of trying to make something go by driving one axle from a belt connected to the other one.

In principle a series of electromagnets could be placed along the track and energised in sequence to pull the train along from one to the next. That's a bit like unwrapping the electric motor and laying it out along the track, and I suspect it would only work with a train that is non-magnetic except for one or more "propulsion lumps" placed in the appropriate positions underneath. My mother-in-law has just had a pacemaker so I must remind her not to travel on one of these...

That certainly works, although it is better done with the electromagnets on the train otherwise you end up using ridiculous amounts of copper. The other member is a simple aluminium plate; the changing magnetic field from the electromagnets induces currents in the plate which create their own magnetic field for the primary field to react against. The fields can be arranged so that as well as providing propulsive force, they also repel each other vertically to lift the train off the track. This is how the "maglev" idea first got going; it arose out of the Tracked Hovercraft project in the late 60s/early 70s thanks to Prof Eric Laithwaite figuring out a better way of doing it.

One of Laithwaite's test rigs was used in a James Bond film to lift and propel a metal tray to chop someone's head off - apparently it's "The Spy Who Loved Me", but I don't remember it.

 

[MarkyT]

That certainly works, although it is better done with the electromagnets on the train otherwise you end up using ridiculous amounts of copper. The other member is a simple aluminium plate; the changing magnetic field from the electromagnets induces currents in the plate which create their own magnetic field for the primary field to react against. The fields can be arranged so that as well as providing propulsive force, they also repel each other vertically to lift the train off the track. This is how the "maglev" idea first got going; it arose out of the Tracked Hovercraft project in the late 60s/early 70s thanks to Prof Eric Laithwaite figuring out a better way of doing it.

One of Laithwaite's test rigs was used in a James Bond film to lift and propel a metal tray to chop someone's head off - apparently it's "The Spy Who Loved Me", but I don't remember it.

The linear induction motor (LIM) is what you're talking about. Its possible track mounted examples of these might be used sparingly at places where trains regularly start from rest such at when departing stations, so heroic feats of acceleration, exceeding the normal limits of adhesion, might be feasible. Installed power on the trains delivered by more traditional traction motors could thus be more limited suitable for maintaining speed between stops and more sedate acceleration from unplanned stops in places where LIMs are not fitted. Track mounted LIMs wouldn't need to be continuous, but could be spaced such that at least some of the reactor plates mounted beneath each car would be above at any time. As long as the train has another source of power it can move forward a short way until a LIM is under a plate so there would be no risk of becoming completely 'gapped'. Vancouver's Skytrain uses train mounted LIMs with a continuous reactor plate between the rails and power supplied by a conventional 3rd rail.

 

[edwin_m]

The linear induction motor (LIM) is what you're talking about. Its possible track mounted examples of these might be used sparingly at places where trains regularly start from rest such at when departing stations, so heroic feats of acceleration, exceeding the normal limits of adhesion, might be feasible. Installed power on the trains delivered by more traditional traction motors could thus be more limited suitable for maintaining speed between stops and more sedate acceleration from unplanned stops in places where LIMs are not fitted. Track mounted LIMs wouldn't need to be continuous, but could be spaced such that at least some of the reactor plates mounted beneath each car would be above at any time. As long as the train has another source of power it can move forward a short way until a LIM is under a plate so there would be no risk of becoming completely 'gapped'. Vancouver's Skytrain uses train mounted LIMs with a continuous reactor plate between the rails and power supplied by a conventional 3rd rail.

As with the French rubber-tyred trains, the flaw there is that the maximum acceleration/braking possible with steel wheel and rail is about the maximum that standing passengers can tolerate. The Paris Metro has signs warning people to hold on because of severe braking.