power/rms/etc (fwd)

• To: tesla-at-pupman-dot-com
• Subject: power/rms/etc (fwd)
• From: Tesla List <mod1-at-pupman-dot-com>
• Date: Sat, 1 Mar 1997 14:06:15 -0700 (MST)
• Approved: mod1-at-poodle.pupman-dot-com

---------- Forwarded message ----------
Date: Fri, 28 Feb 97 07:25:52 EST
From: pierson-at-gone.ENET.dec-dot-com
To: mail11:;;;;-at-us4rmc.pko.dec-dot-com-at-us4rmc.pko.dec-dot-com-at-digital-dot-com;;; (-at-teslatech)
Subject: power/rms/etc

1>         but permit me to show you how an American would make the
1>         calculation:

1>         In a single-phase, sinusoidal ac system of unit power
1>         factor (operating in America),
	Most of the us is on a three phase system, otherwise known as the
	Tesla System...  Many homes and small loads use a single leg.

1>  the current is given by  I  in the following equation:
1>                         I = P/E

1>         The formula says that the value of current in unit amperes
1>         is obtained by dividing the power (in watts) by the potential
1>         difference   E   in volts.

	True Enough, IF the current and voltage are in phase....

!These formulae are quite accurate when applied to DC current and/or
!voltage, but take on a very different guise when applied to AC.
	They apply exactly to AC _IF_ I and E are RMS values.  AND WHEN
	I and E are in phase.
	(If I and E are mixed, the results are hash.  If I and E are peak, the
	peak instantaneous power results, a value which has its uses, but...

!They do not apply the Root Mean Square applicatin which is the difference
!between AC and DC,
	Use of RMS values is _one_ difference between AC and DC notation.
	(DC has an RMS value.  its 1, so its not usual to include it.)

!and they do not account for phase angle compensation
!which can greatly affect instantaneous power, voltage or current.
	yep.

	regards
	dwp

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