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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Microwave oven from 110V to 220V
References: <3DA42F7E.C83136F3@nf.sympatico.ca> <3DA43808.60C7A155@webaccess.net> <3DA46076.D91BDAB2@nf.sympatico.ca> <3DA46E05.65A0FFB5@webaccess.net> <3DA4F585.E2588855@nf.sympatico.ca> <3DA50799.CCB4C933@webaccess.net> <3DA57E42.EBEB0465@nf.sympatico.ca> <3DA58411.2BC5B497@webaccess.net> <email@example.com> <firstname.lastname@example.org> <email@example.com> <3DA6C5E3.F932667C@webaccess.net> <firstname.lastname@example.org> <3DA76CC2.EEDDB6E3@webaccess.net> <email@example.com>
Date: Sat, 12 Oct 2002 01:06:12 GMT
NNTP-Posting-Date: Fri, 11 Oct 2002 18:06:12 PDT
Sam Goldwasser wrote:
> Chuck Simmons writes:
> > You miss my point. The old Ferraris type electromechanical kilowatt hour
> > meter is unaffected by power factor. In at least 40 years I have seen no
> > other type. Even new installations use the Ferraris type because they
> > indicate true power economically. If there is a PF penalty to be
> > applied, the Ferraris meter reads correct power and a KVA meter is used
> > to determine the penalty. In residential areas of the US that have high
> > power factor due to air conditioning and the like, the utility adds
> > capacitor banks for correction. The Ferraris meters read the same either
> > way. I suspect that you have to go back more than 50 years to find a
> > kilowatt hour meter that is affected by power factor in use by US
> > utilities.
> I guess I am missing your point because as far as I can tell, we agree on
> everything. All I am saying is that these power meters do not measure true
> power by some accident (violation of Murphy's law!), they were designed to
> work that way. It's very clever and as you say, economical. If a newly
> minted EE were asked to design a modern replacement, it would likely use
> voltage and current sensing, analog to digital conversion, a microprocessor
> to calculate power, and end up not being as accurate!
Very sorry. Several times in these groups I have seen statements to the
effect that kilowatt hour meters of traditional type do not indicate
true power but rather apparent power such as you would get with a
voltmeter and an ammeter. I incorrectly attributed this to you. You said
it right all along correcting some reference to a more rapidly spinning
meter or some such. I should read more carefully early in the morning.
And indeed the Ferraris type meter is very clever being an integrating
true power meter of very simple construction. One of its virtues in some
power systems is that it is reversible - that is, it "knows" which
direction power is going.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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