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Old January 26th 20, 11:30 AM posted to
Peter Able[_2_] Peter Able[_2_] is offline
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First recorded activity at LondonBanter: Jun 2016
Posts: 71
Default Third rail systems return path

On 25/01/2020 17:33, wrote:
On Sat, 25 Jan 2020 17:23:34 -0000 (UTC)
Anna Noyd-Dryver wrote:
On Sat, 25 Jan 2020 10:58:40 -0000 (UTC)
Anna Noyd-Dryver wrote:
On Fri, 24 Jan 2020 11:18:14 -0800 (PST)
d gone, the majority of the Southern was upgraded to 750 V with the only


maining 660 V sections in inner London (owing to the interfaces with


Underground at Wimbledon and Richmond (because C and D stock were 630 V

its whereas S stock is designed to operate at 750 V) and the fact that

the =

Does the 750V mean only S stock is allowed on the Wimbledon and Richmond
branches now? How does this affect maintenance trains made up of old tube
stock for example?

Anything else which requires to go down there will also have been rewired
appropriately for 750V.

Some of LUs maintenance stock is ancient. I suspect thats a lot easier said
than done.

Anything in use will have had a rewire at some point in the last few
decades because the insulation of older wiring (either VIR or cotton
fabric) degrades over time.

LUs battery locos are now on their third generation of batteries, for
example. The TRC is hauled by 1960 motors; the Central Line RATs are 1962
stock though they don't leave the Central Line.

Well thats the wiring sorted, but I doubt they've changed the motors. Those
are expensive bits of kit to burn out.

Has some risk assessment has been carried out on running sub-750v-rated
motors at a toleranced 750v. Anyone know?

Presumably there has been a lot of sub-750v motors lying around
recently. I wonder if these have been test-energised to, say 850v, to
see if the need to cheaply uprate the very small service stock fleet
could be met by swapping out for a better-than-spec sub-750v motor?

As for battery locomotives, do these float-charge and/or motor directly
from the conductor rail supply, when in use? In other words, what more
than motors might need updating? If enough would the need for change -
at such a high design-cost per vehicle, make it practical to just fit a
DC-DC converter?

Or can they live out their lives, un-modified, running in battery-only mode?