Message 21892 in TECH.WW
From: G8MNY
Date: Tue, 05 May 26 06:50:00 Z
Newsgroups: TECH.WW
Subject: AC Theory
Message-ID: <58918_GB7CIP>
Path: N2MH4|GB7BED|GB7YEW|GB7CIP
R:260508/1449Z 30905@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260505/0651Z 10787@GB7BED.#21.GBR.EU LinBPQ6.0.25
R:260505/0651Z 17965@GB7YEW.#79.GBR.EURO LinBPQ6.0.24
R:260505/0650Z @:GB7CIP.#32.GBR.EURO #:58918 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Mar 08)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
RMS is the DC equivalent power of AC, & for a sine wave is 70.7% of the peak
reading!
325V PK_+ _ +
- \._./ -
0 10mS 20mS Time
POWER V x I POWER V x I
Power Sine Wave
@ 2x Frequency
Unlike DC circuits in AC circuits the power is the mean of the Instantaneous
Power which is made from the instantaneous Voltage X instantaneous Current.
For complex non resistive power loads it is usual to use a term Power Factor to
describe the rating factor to be applied to the RMS Volts X RMS Amps to get the
true power rating. Some items are rated in Watts and some in VA depending on
which is the safer limit for that item.
e.g. a kettle is rated in watts and a transformer is rated in VA.
At power stations the amount of Volt Amp Reactive (VARS) is monitored as an
indication of how much wasted energy flows to & from the customers, just
heating up the transmission system. As the transmission lines are capacitive
some inductive power factor is a good idea as it tunes out this capacitance.
____ ===== ___ =====
Pure Resistive Pure Capacitor Pure Inductor Complex
V _ _ _ _
I _ _ _ _ _
No Current @ 0V + max current @ 0V - max current @ 0V Some current @ 0V
Power_ _ + & - Power - & + Power - & + Power
Power Factor 1.0 Power Factor 0.0 Power Factor 0.0 Power Factor 0.7
PHASE I Current
I
See my Tech buls "Maplin Mains Meter 2000MU-UK", "UK 13A Fused Mains Plug", &
"Tuned Circuit Scope Demo".
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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