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Transformers in electric trains?

  1. May 20, 2006 #1
    I have an exam on monday and looking through the past papers I came across a question I couldn't find a suitable answer to:

    List the economical advantages of using a transformer in a train rather than run the overhead lines at 400V?

    any help would be very much appreciated.........

    Phil N
  2. jcsd
  3. May 20, 2006 #2


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    Staff Emeritus
    Science Advisor

    Well very simply, overhead lines carry electrical current long distances and since Power = Current * Voltage (for AC it's an integral of I(t)*V(t), but essentially the same principle), the current is reduced as voltage increases.

    So to minimize power resistive (I2R) and reactive losses, high voltage is used. In the transformer the high voltage is reduced (dropped down) to a voltage suitable for a motor.
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