News for hackers. Stuff that matters.

A comment on Cooling the tube – Engineering heat out of the Underground. Parent comment

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.
[ Parent | on HN ]
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.

[ Parent | on HN ]