Manual switching is not fast enough - regen was always a problem on LUL due
to conductor rail gaps and no through train power bus being allowed.

It has become viable with solid state switching which is fast enough to
detect the gap and virtually instantaneously divert the current to braking
resistors, etc on the train (temporary loss of braking would be undesirable,
at the least!).

Taking this a stage further it would be relatively straightforward to detect
whether the negative rail is at LUL type potential (i.e truly a negative
rail) or at earth potential as on NR tracks. I don't know if this is the
way it is going to be done, but is certainly feasible.

Peter

PS I presume that regen will not be allowed on NR sections due to the
potentially enhanced performance of "conventional" NR stock in the section
when regen is taking place.
--
Peter & Elizabeth Corser
Leighton Buzzard, UK
"Tom Anderson" wrote in message
h.li...
On Mon, 13 Nov 2006, TheOneKEA wrote:

While doing a bit of idle research into the upcoming Standard Stock (aka
'S' Stock) being designed for the Underground's Sub Surface Lines, I came
across an interesting note which stated that regenerative braking is to
be provided and used by the S stock on the SSL lines,

At last!

and _only_ on the SSL lines - the S stock running District Line services
to Richmond and Wimbledon will not regenerate when they are on NR metals.

ISTR a Doctor Who season finale along much the same lines.

Sorry.

I'm guessing that the trains will achieve this by using some kind of
mechanism which can detect the voltage level of the negative pole of the
traction circuit and subsequently cut in the regen mechanism when the
negative pole is within the appropriate voltage range. Does anyone know
how this could be accomplished?

Using the running rails as a voltage reference would be the obvious way to
do it. AIUI, there is a voltage across them from track circuits, but it's
small enough that it shouldn't matter.

However, i wouldn't be at all surprised if the way it actually worked was
that the driver had to flip a switch to turn the regenerator off!

tom

--
Osteoclasts = monsters from the DEEP -- Andrew




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