On Sydney trains the C sets and the Tangara's use a chopper. If you
are on a Sydney station (underground especialy) the sound of the
chopper trains has a bit of a little whine about them compared to the
older trains. Also one outer suburban Tangara has AC traction motors
that provides a different whine althogether!!
The older trains use a resistor bank to provide a varying current or
voltage (not sure which) to allow the train to accelarate.
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Ashley Wright, Sydney, soon to be Canberra, Australia
ajwright@ozemail.com.au
www: http://www.ozemail.com.au/~ajwright
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