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From: roy@phri.nyu.edu (Roy Smith)
Newsgroups: sci.electronics
Subject: Re: Urban Myths again
Message-ID: <1990Apr12.170353.23722@phri.nyu.edu>
Date: 12 Apr 90 17:03:53 GMT
References: <1209@gtx.com> <14306@lambda.UUCP> <1646@rsiatl.UUCP> <8830@pt.cs.cmu.edu>
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Organization: Public Health Research Institute, New York City
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In article <8830@pt.cs.cmu.edu> rwb@vi.ri.cmu.edu (Bob Berger) writes:
> Don't dismiss this "wattless" power so quickly. It is exactly what you
> are charged for by the utilities meter [...] The rate at which the meter
> turns is proportional to the volt-amperes of apparent power.

	Sorry, but this is just plain wrong.  Watt-hour meters read actual
true power, V*I*cos(theta).  The "wattless" power, known in the vernacular
as VARS (Volt-Amps Reactive) does not register on the meter.

	If you are an industrial user, the power company may monitor your
power factor (the cos(theta) mentioned above, where theta is the phase
angle between the voltage and current vectors) and get on your case (i.e.
charge you extra) if it gets too low, but the Watt-hour meter *still* reads
true power.  VARS are bad because while they don't constitute any real
power that you are consuming (and thus being charged for), they do increase
the current draw, and lead to larger resistive losses in the power
distribution grid.  In the ultimate nightmare scenario, it may even cause
the generators to loose sync, at which point you are only happy if you own
stock in candle and flashlight battery companies.
--
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
"Don't Worry, Be Happy"