Originally Posted by
old kodger
As I said, YOU DON'T LISTEN, "(240 volt delta or 415 volt star)?" 240 volt STAR, 415 volt DELTA! And it would seem from your question that you don't know much about electric motors either, so I will presume to teach my granny how to suck eggs.
Star connected motors have three legs each having L1,L2,L3, (in Australia, 240volts each) the common neutral for all three legs is the central star point.
I have no idea how motors are wound in America, but I can see no reason why they would be any different to Australia except to allow for the different potential .
Each winding is center tapped, the tap is the end point of the three legs (L1,L2,L3). In "star" the other ends are connected together to form the center point, giving tree pairs of windings, each pair being in parallel, and individual winding being rated for the incoming voltage (240)
In delta the center taps are still the L1,L2,L3 connections, but the other ends, instead of being connected to a common point, each individual half of a winding (still rated for 240 volts), is connected to half of an adjacent winding giving three windings comprising two individual components rated at 240 volts but in series thereby achieving a rating of 480 volts between any two center taps (it happens that two 240 volt phases, 120 degrees apart will give rise to a voltage between them of 415, but that is not relevant to the question).
It can be seen from the foregoing that a 240/480 volt transformer, center tapped on it's secondary, will effectively give two 240 volt legs 180 degrees apart relative to the center tap. I readily concede that, that will only energize one phase of a delta connected motor, but used exactly as your L1 and L2, using the center tap as the star point will energize two legs.
Now Mr Junkers2, my time is not free, so if you would be kind enough to send me a cheque for $50 for that piece of education, it would be much appreciated.
Regards,
Old Kodger.
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