>-----Original Message-----
>From: Howard Winter [mailto:HDRW@H2ORG.DEMON.CO.UK]
>Sent: 26 May 2004 15:38
>To: PICLIST@MITVMA.MIT.EDU
>Subject: Re: [EE:] power factor change depending on voltage or phase?
>
>
>Michael,
>
>On Tue, 25 May 2004 08:17:28 +0100, Michael Rigby-Jones wrote:
>
>>...<
>>
>> Just to add that in the UK, industrial installations use a
>415 volt 3
>> phase connection almost exclusively for any high current machinery.
>
>Indeed, but as far as I know we never do the American trick of
>connecting across two phases.  In fact domestic supplies are
>almost always just single phase (nominally 230V these days,
>but actually nearer 240 - in fact my UPS reports it at 243.1
>at the moment).
>
>Incidentally, is there an easy way to calulate RMS / Peak
>voltage from each other in a single phase supply? How about 3
>phase?  (I never was much good at AC - give me DC and Ohm's
>law any day :-)

RMS = SQR(2) * Vpeak

For 240volt RMS, this gives a peak of around 340 volts.

The voltage between two phases of a 3 phase supply (the "line" voltage) is
SQR(3) * Vphase.  For the UK system this gives 240 * 1.73 = 415volts.

The change from 240 to 230 volts was a paper exercise only to unify the
voltages across Europe. No voltage were actually changed, just the allowable
tolerance.


Regards

Mike






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