Re:Cooling the tube – Engineering heat out of the Underground
by crote on Saturday June 24, 2017 @07:42AM
(#14625271)
Correct me if i'm wrong, but it seems that regenerative braking is a bit troublesome because it is a third rail direct current system: a "regular" AC system can simply feed power back through the transformers to the power grid, but this is not possible here, so power must be consumed by another train fed by the same rectifier.
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Re:Cooling the tube – Engineering heat out of the Underground
by mhb on Saturday June 24, 2017 @09:41AM
(#14625539)
You're not wrong:
However, that [regeneraative braking] can only work where trains are accelerating and braking at the same time, on the same electricity sub-station loop.
Re:Cooling the tube – Engineering heat out of the Underground
by ams6110 on Saturday June 24, 2017 @03:29PM
(#14627085)
Or something like super capacitors to hold the braking energy until the train needs to a accelerate again
Re:Cooling the tube – Engineering heat out of the Underground
by hydrogen18 on Saturday June 24, 2017 @07:58AM
(#14625299)
It would be much more difficult to feed power back into an AC grid from a regenerative brake. With a DC grid, no synchronization is needed.
Re:Cooling the tube – Engineering heat out of the Underground
by F_r_k on Saturday June 24, 2017 @08:18AM
(#14625338)
That's not true.
1) modern railway is fully IGBT powered. In this case it is trivial to inject current.
2) with DC current you need a substation capable of converting AC to DC (easy: bridge rectifier) but also DC to AC (to given tolerances) which is much more cumbersome.