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Hi, thanks very much to the person who explained about the 3 phase AC traction motor on the train where the direction of motor spin, depends upon what order the 3 power supply phases are applied to the motor.
I know that a DC motors direction depends upon the polarity of the DC voltage applied to it.
But how about a single phase AC motor? The polarity is constantly changing as its AC current and also its only one phase here, so the order of phases applied can't be used here? Interesting question.
I looked this up in a science book a minute ago out of interest as I was bored at work today and had to keep my brain active. Maybe its down to at what part of the AC cycle the voltage is applied at? Such as on the positive cycle of halfway through the negative part. Wonder if the starting position of the motor matters?
Cheers...
atsf3751 Member # 1538
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The ideal AC traction locomotive would have single-phase traction motors. However, they have not been able to overcome the problem of controlling the direction of the current, so for right now, railroads and builders seem to be happy with building 3-phase motors. Perhaps a bit inefficient, but they get the job done. I don't know how close they are to developing a single-phase motor, especially with the AC market cooling off somewhat in the past year or so, and many major railroads going back to purchasing DC locomotives.
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