Howard Winter <HDRW@H2ORG.DEMON.CO.UK> wrote:
> This has always perplexed me: surely if you're connecting across 2 of 3
> phases (something we don't do in the UK) then the voltages are at 120
> degrees phase angle to each other, so you will be getting a distorted
> waveform, not a sine wave?

Check your math. The sum (or difference) of any two sinewaves at the same
frequency, regardless of relative phase or amplitude, is still a sinewave.
This is the whole basis of Fourier analysis.

> Incidentally, is power factor correction (PFC) a Good Thing for the user
> (ie. does the meter go round less for a given power used) or for the
> supplier (the meter goes round more)?

A power meter measures instantaneous real power, which is then averaged by
the mechanical inertia of the disc. PFC does not affect this measurement
(or at least it should not in theory -- there may be secondary effects
that create a small difference), but it makes the power company happier by
reducing the resistive losses in their distribution network.

For more details, which will also help Al, see questions 6 to 8 here:

   http://www.circuitcellar.com/library/eq/156/index.htm

-- Dave Tweed

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