Latest Voltage Transformer System News

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SBB – Traction Current Transformer
, Latest Voltage Transformer System News
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Because the railway systems are powered by electricity from the local network, there are these transformers on the catenary masts for an uninterrupted power supply. So the trains can continue to run in a local power failure as long as traction current is present.
With these transformers, the traction current of 15’000V is downranged to 230V or 400V, depending on the system. The UPS divides the load about 50% between both networks. If one network fail, the other network takes on the whole load. Depending on the system generation and configuration, there are additional batteries available. The types of current and voltages of the railway systems are local very complex and different.
Normally, the railway switch drives are supplied with 3x400V AC for the changeover process and the monitoring current is 48V DC. But in Oberriet there is still a plant where there is used 1x 230V AC for the changeover process and 36V DC for monitoring. There is also no UPS, but net toggles. If the 50Hz local network fails, the load is switched directly to 16.7Hz. Because the railway switch drives are single-phase in these systems, this does not matter. The railway gate drives are single-phase all over. In Oberriet and Rüthi there is one rectifier each on the 50Hz and on the 16.7Hz network. If the 50Hz net fails here, the pre-signals flicker in the "Warning" position, because in this switching state AC voltage is delivered to the pre-signal. All other signallings on the pre-signal as well as all dwarf and main signals are fed with DC.
In some stations, also the turnout heaters are operated by traction current, so there are several such transformers as in Sargans. Now you can see how easy it all is, if once again a malfunction at the railway system is announced. Switzerland, April 16, 2019.

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