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Post by q8 on May 10, 2005 17:55:43 GMT
A thought just occurred to me about Thyristor control of trains. In the 70's they had a 1962 stock unit on the Central that was fitted with experimental chopper control. This made a loud buzzing noise.. They also decided to test it on other parts of the system running empty. When it was used at the east end of the District (the high class end) it was found to return the signals on the LTSR side to danger as it passed. What was the cause of that and has it been rectified since? If the new SSL stock is to be chopper controlled obviously they don't want to cause cock ups on NR do they (or do they)
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Colin
Advisor
My preserved fire engine!
Posts: 11,346
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Post by Colin on May 10, 2005 18:29:05 GMT
Sounds a bit complicated for my little brain!!  I know that when c2c introduced their class 357's they affected the District signals. They also had problems with our traction current affecting their onboard computers. That was their excuse when they first used them anyway. I would imagine they'll always get these problems with new stock, it's a case as find out when you use it! ;D ;D |
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Post by igelkotten on May 20, 2005 11:24:01 GMT
Without delving into waveforms and complex equations, basically thyristor controlled vehicles are more "noisy" when it comes to electromagnetic fields, than a electromechanically controlled vehicle, especially one with DC motors.
They give off stronger EM fields, or at least fields that have a much wider spectrum of frequency and intensity than the ones from traditional electrics. This also applies to return currents, which means that if you use your running rails as a return path, you might get problems with your track circuits and earth bonds, since they might be subject to currents or frequencies they are not designed for.
Likewise, the traction current load might be of a different profile -the new C20 stock in Stockholm, for example, draws overall less current than the old stocks, but has much higher peak loads when accelerating. This can also lead to problems with the power supply and return, something that again also can interfere with signalling circuits.
Here in Sweden, the mainline railways had to change out certain types of track circuits during the late 1960'ies-early sevenites, as the thyristor controlled Rc series of locomotives became the standard locomotive. For us in the tube, things were simpler, since our track circuits operated on a slightly different principle, and were of a different design.
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