Why LGB catenary still requires track power?

Mobi

Mobi

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I don't use catenary myself but I understand it sill requires track power.
But why so? Why can't it run on catenary power alone like real life electric locos?

If this is to complete the circuit, how does real trains do it without having to power the tracks?
If you lay the track on soil with rails touching ground, is it not going to complete the circuit?
 
The rails provide the return current ............... in both cases.

On the 1:1 railways, the metal rails are supported by either timber or concrete sleepers.

There are some railway lines that use metal sleepers (not usually on main lines) and clearly, this wouldn't work with overhead or third rail electric power :oops:
 
The model trains using catenary work in exactly the same way the real ones do. The metals wheels and rails of 1:1 trains pass the current back to the substation after pulling it off the overhead wire to power the motors. Model trains do the same. The actual ground does not complete the circuit.
 
Mobi said:
If this is to complete the circuit, how does real trains do it without having to power the tracks?
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the train does it with powered track. but people don't feel anything, because most are not able to step with one foot on the rail, while touching with the other the catenary.

being a model, or a 1:1 thing, it is all the same.
one cable (with DC the positive) runs through the catenary.
the other cable runs through the "earth".
it does not matter, if "earth" is just one rail, or the entire 1:1 globe.

here, in the 3rd world, we had a rural telephone, that worked with one cable only.
(at the central one cable was connected per steel wire on posts to the individual telephones, the other cable was stuck into the earth. at the individual phones it was the same: one contact to the steel wire, one contact stuck into the earth.
in 1984, when we built a 5 mile/8 km line for electricity (20,000V AC) from the next village with electricity to our village, we put up just one aluminium cable.
at the transformer to 220V AC in our village, there we got some fuses and a cable, that went into the earth till the groundwater level.
that worked for 30 years, till we got concrete posts with three cables.

in the model the good idea of this system is, that you can use two controllers (one connected as plus to the catenary, one connected as plus to one rail and both connected as minus to the other rail) and have two trains going at different speed (or even in different directions - for the Addams effect) on the same stretch of track.
 
Looking at RhB catenary closely you can see a return wire on the back side of all uprights. The cable with no insulator about 3/4 the way u[ the poles.
The rails and ground are in the return circuit, in there system the rails and the ground wasn't a good enough return path all the way back to a tx or hydro generator and a dedicated return cable is also run.
Just to muddy the waters.
 
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My (limited) understanding as that the catanary powered a loco using an appropiate pantograph while if there were also power to the rails, these would allow track-powered locos to be operated as well.

A passing thought, would a diagrammatic representation of audience attendances over the years at "Cinderella" be a pantograph?
 
playmofire said:
My (limited) understanding as that the catanary powered a loco using an appropiate pantograph while if there were also power to the rails, these would allow track-powered locos to be operated as well.

A passing thought, would a diagrammatic representation of audience attendances over the years at "Cinderella" be a pantograph?
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I would assume LGB and compatible electric locos, with a wired pantograph, will be wired to the same + source as on 1 one of the rails, not the - return. All you have to remember is that you haven't reversed the polarity at track level to the side opposite to that the pantograph is picking up is linked to. Or am I misunderstanding something here ? Max
 
So in real electric loco, if the tracks were made of wood or non-conducting materials (assuming it can bear the weight) then circuit won't be complete and train won't run?
 
playmofire said:
My (limited) understanding as that the catenary powered a loco using an appropriate pantograph while if there were also power to the rails, these would allow track-powered locos to be operated as well.
Click to expand...
Long ago (late '50s/early '60s) I did that with Maerklin. Steam/diesel powered off the centre studs, eloks off the catenary; running rails formed the return in both cases. The eloks had a switch for either stud or catenary power. One could wire up signals and insulated sections to allow trains of either sort to follow one another without rear-ending. IIRC, one could also arrange signals and track loops to allow trains to run in opposite directions automatically without doing an Addams.
 
Mobi said:
So in real electric loco, if the tracks were made of wood or non-conducting materials (assuming it can bear the weight) then circuit won't be complete and train won't run?
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Correct.

The current has to flow around the circuit. In effect, it has to come from somewhere, and go back to somewhere.

(The Physicists are reaching for their keyboards, even before I hit 'Post') :giggle:

PhilP.
 
PhilP said:
The current has to flow around the circuit. In effect, it has to come from somewhere, and go back to somewhere.
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i'm neither a physicist, nor a sparky, but for my last layout i had asked a lot of questions from sparkies.
seems, that PhilP nailed it. (i might add: " from and to the same somewhere")

following the LGB colour code for cables i had my track coded red for DC +, and blue for DC -.
and just for the beauty of it (and to save many feet of cables) i used the "blue" rail as (omni)bus for other things too.

1) my six blocks of track had an independent controller each. connected to the "red" rail of that block. the "blue" rail of all six blocks together were connected as one common bus - connected back to each of the controllers. (it seems, the electrons got enough intelligence to find "their" controller on their own) :giggle:
2) the black cable between the 16V AC transformer and the reed switches. (the orange and the white cables i had to lay separately)
3) various independent light blue cables for house lighting (from 8V DC transformers to the blue rail and from there to christmas chain cut offs in the houses - the yellow back line went direct)
4) one experimental circuit (from Todd, short isolated, less than an inch long isolated pieces of "blue" rail, connected to green cables going to components of 12V DC central locks for cars to switch on or off animations. - the brown cables went directly back to the 12V DC source)

this trial and error installation must have saved me about 2 to 3 hundred feet of cables. (the layout had more than 400 ft of track)
 
Software Tools said:
That is a safety ground wire to ensure that the stanchions supporting the OCS are assuredly at ground potential, it is not intended as a traction power circuit return.
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The info I found said it was also a return in the mountainous areas. As the ground is not good for ground current flow, as well as a ground potential wire for the poles.
Looking at the cables it appears to be the same diameter as the overhead supply cables?
 
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If you have had to walk to a dodgem car on the metal floor that’s the return path. Electric locomotives work on the same principle. The centre of loco axles have a big set of brushes so that the return path is not through the axle bearings.
 
grizzmo said:
The info I found said it was also a return in the mountainous areas. As the ground is not good for ground current flow, as well as a ground potential wire for the poles.
Looking at the cables it appears to be the same diameter as the overhead supply cables?
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Yes, because there is a lot of power going through them and there's probably a long runof cable. On something like a railway, small cables can easily get damaged too
 
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