>-----Original Message-----
>From: Howard Winter [mailto:HDRW@H2ORG.DEMON.CO.UK]
>Sent: 24 May 2004 15:03
>To: PICLIST@MITVMA.MIT.EDU
>Subject: Re: [EE:] power factor change depending on voltage or phase?
>
>
>Al,
>
>On Wed, 10 Mar 2004 07:11:19 -0800, al smith wrote:
>
>> I did some measurements, where I found peak current for
>122VAC single
>> phase to be 1.554A being pulled on the AC, and then did the
>same test
>> using 212VAC (two legs of a 208 3 phase) and found the AC
>current draw
>> to be 0.935A
>
>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?
>
>> Thus wattage is 189.6 for single phase, and 198W for the '3phase'.
>> Pretty close in value, although I might expect them to be
>pretty much
>> the same, since the same load was applied.  So thats the
>first curious
>> item.
>
>Unless you're using "True RMS" meters, I think the distortion
>I mention would mean that the readings would be skewed.


The voltage across two sinusoid with a constant phase difference is also a
pure sinusoid.  The voltage obviously depends on the phase, from 0v @
0degrees to twice the voltage of one phase @ 180 degrees.

Regards

Mike




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