Dragged Pendelinos

[CosherB]

....And other locos or trains with traction motors. I presume these motors are still geared to the axles during the drag. Does this cause much more effort to be required by the loco pulling the train, and does it cause much extra wear having the wheels turning the transmission and motors for extended periods, rather than the other way round?

Does anything have to be done electrically with the commutator and field windings to limit drag and the possibility of overheating?

 

[Crossover]

There is a chance if an electric train is dragged and traction motors are left engaged, it could be used to the opposite effect and act a generator to power onboard equipment when not on the OHLE as various motors can act as both.

Whether this actually happens would have to be advised by someone with more knowledge, but was just a thought anyway

 

[Old Timer]

You do not engage or disengage electric traction motors. When turning without an input they effectively become a generator. They will thus in effect create a degree of "drag" (resistance) but you would need someone who is more knowledgeable than me on traction systems to tell you more

The traction supply to the traction motors is completely separated from the domestic supply, which is tapped from a different connection off the main transformer.

 

[NightatLaira]

I can remember when the London Euston to Holyhead Pendolinos were routinely dragged by 57s north of Crewe. I think they've switched completely to Super Voyagers now - it would be interesting to see if the electrical systems were boosted by the 'generator effect' of the dragged traction motors or whether all the electricity on bard came from a wire tap to the 57.

[note to moderators - feel free to merge this topic withhttp://www.railforums.co.uk/showthread.php?t=35282 ]

 

[Old Timer]

The 57s will only provide an ETS supply for the train air con, train lighting, pa/internal comms systems, and restaurant car supply.

The rotation of the dead traction motor wheels will cause the generation of an electrical supply but that will simply run back to the main transformer taps and feed into the secondary windings there. In theory (and practice) it is possible for the secondary windings to energise the primary windings which would cause the Pan to become charged but with a low value current whilst the train is running.

The accuracy of this would need to be validated by a traction & rolling stock engineer though, as I do not have much knowledge on the control systems.

 

[John Webb]

The electric motors would be isolated from the supply in a train being towed. There may be some residual magnetism in the steelworks of a motor, but this is likely to be low, so while a motor being turned might generate some electricity, it would be at a low voltage and current. And because the motors are electrically isolated this will not be fed back into the supply.

(I have a feeling that some people may be getting confused with 'regenerative braking' where indeed the motor control system does arrange for motors to act as generators to feed power back to the supply and slow the train down.)

I suspect the main cause of additional drag will be the resistance of the gearing from the wheel axle to the motor shaft.

 

[NightatLaira]

I suspect the main cause of additional drag will be the resistance of the gearing from the wheel axle to the motor shaft.

So there's no way of disengaging the wheel axle gearing from the motor shaft and reducing the drag?