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G8MNY > TECH 20.03.05 23:44l 81 Lines 4180 Bytes #999 (0) @ WW
BID : 37713_GB7CIP
Read: DK7JAN GUEST
Subj: AC Theory
Path: DB0FHN<DB0NOE<DB0GAP<DB0FSG<DB0MRW<DB0WUE<DK0WUE<I0TVL<ED1ZAC<GB7YKS<
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Sent: 050320/1900Z @:GB7CIP.#32.GBR.EU #:37713 [Caterham] $:37713_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Dec 04)
RMS is the DC equivalent power of AC, & for a sine wave is 70.7% of the peak
value. eg the peak value is û2 (1.414) time bigger than the RMS meter reading!
340v PK_+ _ +
240v____³ /' '\ Sine Wave 240v 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 ³ ³ ³ ³ _³_________
³ ³ ³ ³ ³ 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.
eg. a kettle in watts & a transformer in VA.
At power stations the amount of Volt Amp Reactive (VARS) is monitored as a
indication of how much wasted energy flows to & from the customers, just
heating up the cables.
____ ===== ___ =====
ÄÄÄ´____ÃÄÄÄ ÄÄÄÄ´ÃÄÄÄÄ ÄÄÄ())))ÄÄÄÄ ÄÄ´___ÃÄÄ())))ÄÄ
V Pure Resistive Pure Capacitor Pure Inductor Complex
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 \,_,/ ³ \,_,/
I IN PHASE LEADING 90ø LAGGING 90ø AT SOME ANGLE
³ _ _ _ _ _
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
³ _ _ ³ + & - Power ³ - & + Power ³ - & + Power
³ / \ / \ +³ Zero Net power +³ Zero Net Power +³ _ _
³ ³ ³ ³ ³ ³ _ _ ³ _ _ ³ / \ / \
³ ³ ³ ³ ³ ³ / \ / \ ³ / \ / \ ³ ³ ³ ³ ³
³_/_ _ _\_/_ _ _\_ ³³ _ ³ _ ³ _ ³ _ ³ _ ³ _ ³ _ ³ _ ³ ³ ³ _ ³ _ ³ _ ³ _
³ Always Positive ³ ³ ³ ³ ³ ³³ ³ ³ ³ ³ 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
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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