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G8MNY > TECH 21.11.18 10:02l 86 Lines 4451 Bytes #999 (0) @ WW
BID : 46270_GB7CIP
Read: GUEST
Subj: AC Theory
Path: IW8PGT<IR2UBX<SR1BSZ<GB7CIP
Sent: 181121/0800Z @:GB7CIP.#32.GBR.EURO #:46270 [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
value. e.g. the peak value is û2 (1.414) time bigger than the RMS meter
reading!
325V PK_+ _ +
230V____³ /' `\ Sine Wave 230V DC_³__________
RMS ³ ³50 Hz³ MAINS ³ D C
0vÄ´³- - - -³- - - -³ 0vÄ´- - - - - -
³ A C ³ ³ ³
- \._./ -
0 10mS 20mS Time
POWER V x I POWER V x I
³ _ _ ³
³ / \ / \ ³
MEAN_³ Þ Ý Þ Ý _³__________
³ Ý Þ Ý Þ ³
³_/_ _ _\_/_ _ _\_ ³_ _ _ _ _ _
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 & some in VA depending on
which is the safer limit for that item.
e.g. a kettle is rated in watts & 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.
____ ===== ___ =====
ÄÄÄ´____ÃÄÄÄ ÄÄÄÄ´ÃÄÄÄÄ ÄÄÄ())))ÄÄÄÄ ÄÄ´___ÃÄÄ())))ÄÄ
Pure Resistive Pure Capacitor Pure Inductor Complex
V _ _ _ _
³ /' `\ ³ /' `\ ³ /' `\ ³ /' `\
³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³
´³ - - - ³ - - - ³ ´³ - - - ³ - - - ³ ´³ - - - ³ - - - ³ ´³ - - - ³ - - - ³
³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³
³ \._./ -³ \._./ ³ \._./ ³ \._./
I IN PHASE I LEADING 90ø I LAGGING 90ø I @ SOME ANGLE
I _ _ _ _ _
³ /' `\ ³ `\ /' ³ /' `\ ³ /' `\
³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³
´³ - - - ³ - - - ³ ´ - -³ - - - ³ Å - -³ - - - ³ - - Å ³ - - - ³ - - -
³ ³ ³ ³ ³ ³ ³ ³ ³ ³³ ³ ³
³ \._./ ³ \._./ ³_./ \._ ³ \._./
No Current @ 0V + max current @ 0V - max current @ 0V Some current @ 0V
Power_ _ + & - Power - & + Power - & + Power
³ / \ / \ +³ Zero Net power +³ Zero Net Power +³ _ _
³ Þ Ý Þ Ý ³ _ _ ³ _ _ ³ / \ / \
³ Ý Þ Ý Þ ³ / \ / \ ³ / \ / \ ³ Þ Ý Þ Ý
³_/_ _ _\_/_ _ _\_ ³ _ Ý _ Þ _ Ý _ ³ _ Þ _ Ý _ Þ _ Ý ³ Ý _ Þ _ Ý _ Þ _
³ Always Positive ³ Þ Ý Þ Ý ³ Ý Þ Ý Þ ³/ \_/ \_/
³ ³ \_/ \_/ ³ \_/ \_/ ³ some net power
³ -³ Equal + - power -³ Equal + - power -³
Power Factor 1.0 Power Factor 0.0 Power Factor 0.0 Power Factor 0.7
PHASE I Current
<-. /³\ Current ÚÄÄÄÄÄÄÄ>V Lagging
Rotation `\ ³ Leading ³90ø Current ,ÄÄÄÄÄÄÄÄ>V
| ³90ø ³ Lagging `-._ í Angle
o ÄÄÄÄÄÄÄ>V & I ÀÄÄÄÄÄÄÄÄ>V \³/ `->I
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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