OT: Declan and quantum physics

Andrew Calkin calkin at ieee.org
Thu Jul 24 04:01:01 PDT 2003


On Thu, Jul 24, 2003 at 12:37:22PM +0200, Jochen Schroeder wrote:
> Ian Molton wrote:
<big snip>
> > On Wed, 23 Jul 2003 22:58:47 +0000 (UTC)
> > dagmar.wants at nospam.com (Dagmar d'Surreal) wrote:
> > 3 phase is supplied with each wire carrying a signal 120 degrees out of phase from the previous one.
> > 
</big snip>

That's what I was taught in my power engineering lectures at uni. There is
a central tap on the generator, and 3 taps on the rotating thing (stator? I'm 
not doing power so I forgot the terminology), which each have a voltage 120 
degrees phase difference between the 3, and the voltage difference is 
between the 3 outer taps and the central tap.

<big snip>
> It *is* nice to be able to actually get 3-phase into the home (if thats what
> you actually get in the USA). Here we only get 1 phase, albeit at 240V so we
> dont need another just to run the washer-drier...
</big snip>

>From memory, power distribution companies usually send 3 phases into every 
house in a street, because they need to balance the load. This is because a 
lot of the consumer appliances tend to be inductive loads (motors are an 
example), whereas things like lights are generally resistive (incandescent) or
inductive with capacitive balancing (flourescent {sp?} ), so that the relative
phase between the current and voltage is not thrown too far out, resulting in
lost power (or low power factor, cosine of the angle or phase between current
and phase). So you should have 3 phases in your house. But I may be wrong, of
course ;-P

I think the only thing about 3 phase instead of single phase with respect to
single phase is that you don't require a starter circuit with 3 phase, but 
it is needed with a single phase supply.

//Andrew
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