From: "Olin Lathrop"
Subject: Re: [EE:] 110v olt motors on 230v mains


> Robert Rolf wrote:
> > They'd be more efficient at 230V since the I^2R losses
> > would be less with a lower operating current.
> > You would save watts be having less heating.
>
> Not really.  Consider a coil producing a certain strength magnetic field
at
> 220V.  Now consider how to create the same magnetic field with 110V
starting
> with that coil.  If you cut the coil in half, you have two 110V coils each
> producing half the required magnetism.  To run these at 110V, you have to
> put them in parallel instead of series.  Each individual coil has the same
> current and therefore the same I^2R losses, and the total magnetism and
> power are the same.

But, you have 2 coils in parrallel, so there are twice the I^2R losses
overall...

Think about why we use high voltage to transfer power - because for a given
power P=VI at the end of the line, if you double the volts, you half the
current. If you half the current, you loose 1/4 of the power you would have
lost.

Cheers.....Mike.



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