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Post by silenthunter on Aug 19, 2017 16:10:57 GMT
Why did you sometimes have the lights go out on the Underground trains then come back on a few seconds later?
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Deleted
Deleted Member
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Post by Deleted on Aug 19, 2017 16:31:25 GMT
Going over a sub station gap
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North End
Beneath Newington Causeway
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Post by North End on Aug 19, 2017 16:43:53 GMT
Why did you sometimes have the lights go out on the Underground trains then come back on a few seconds later? On older trains the lights are fed directly from the motor alternator sets, which are themselves fed directly from the traction current rails. Therefore whenever there is no power, for example when that particular car passes over or stops over a gap in the current rails, the lights go out. There are some things which have been done to improve upon this setup, like feeding half the lights from one MA and half from another, so reducing the chances of everything being lost. More recent trains have an auxiliary converter feeding the lights via a battery charger, which keeps the lights on even if the auxiliaries are not being fed. Naturally there is a time limit attached to this, but long enough that it should cover normal situations like passing over pointwork. It's still possible to have lights go off on something like a 95 stock if the train stops long enough in the wrong place, more likely if shoes are missing on one of the driving cars as this is where the auxiliaries are fed from. |
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Ben
fotopic... whats that?
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Post by Ben on Aug 19, 2017 19:34:03 GMT
One wonders if, with the advent of low power LEDs and super capacitors, it would be possible by circuit redesign to eliminate all blackouts all together.
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Post by rsdworker on Aug 19, 2017 21:17:23 GMT
A and C and i think D stocks did this - some half lights go off and half lights on but while in deep tubes - its very rare to have half of lights go off - the refurbished deep tube stock now dont go off straightaway
but however not sure about S stocks - i think new all connected in one unit
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Post by zcap on Aug 20, 2017 9:03:50 GMT
I rather enjoy when the lights go out on '96 stock, it reminds me that they are getting old. As old as me  But, in all seriousness, its getting more and more common now on stocks like the '96 stock, which, im not particularly against. The short bouts of darkness are quite fun imo. Not so recently, I got on a '95 stock at Waterloo towards Warren Street, and all the lights in the first carriage were out except two by the interconnecting doors. I sat by the cab and just enjoyed the ride in the darkness.  |
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North End
Beneath Newington Causeway
Posts: 1,769
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Post by North End on Aug 20, 2017 11:28:17 GMT
I rather enjoy when the lights go out on '96 stock, it reminds me that they are getting old. As old as me But, in all seriousness, its getting more and more common now on stocks like the '96 stock, which, im not particularly against. The short bouts of darkness are quite fun imo. Not so recently, I got on a '95 stock at Waterloo towards Warren Street, and all the lights in the first carriage were out except two by the interconnecting doors. I sat by the cab and just enjoyed the ride in the darkness. Lights going out over gaps shouldn't happen on 95 and 96 stock, as they should be supplied by battery - unless the train actually stops with car 1 or 6 off current for more than about 20 seconds. If it happens momentarily when moving then the train has a major defect. If you had no lights going north from Kennington, it may well be that the motorman had switched off the lights as part of the detrainment process before going round the loop and then forgot to put them back on again. Unlike some other trains it's theoretically never possible to put a 95 stock in complete darkness, the emergency lights should remain on no matter what, unless there is a battery problem (or the tubes concerned have blown!). If it was a genuine defect causing the lights to be off, you might enjoy the experience but it could signify the train has a defect that has not been correctly responded to by the driver. For it suggests the train is running with at least one auxiliary converter and compressor not working, maybe even both of each. In this situation the train should be out of service as if something goes wrong with the other end of the train then the train is very likely to soon become stranded. This happened approaching Finchley Central a few years ago, the train started going wrong at Archway and the driver correctly wanted to take it out, but service control cajoled the driver into keeping it in. Had it been empty it would likely have reached Finchley Central siding before the main line air went too low, but as it happened the train died approaching Finchley Central and shut the job down for over an hour, complete with a train load of highly unimpressed punters! |
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