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Formulas

When a voltage V causes a current I to flow through a reactive load Z, the complex power S is:

S = VI* where I* is the conjugate of the complex current I.

Inductive Load

Z = R + jXL

I = IP – jIQ

cosf = R / |Z| (lagging)

I* = IP + jIQ

S = P + jQ

An inductive load is a sink of lagging VArs (a source of leading VArs).

Capacitive Load

Z = R – jXC

I = IP + jIQ

cosf = R / |Z| (leading)

I* = IP – jIQ

S = P – jQ

A capacitive load is a source of lagging VArs (a sink of leading VArs).

NOTATION
The symbol font is used for some notation and formulae. If the Greek symbols for alpha beta delta do not appear here [ a b d ] the symbol font needs to be installed for correct display of notation and formulae.
B
C
E
f
G
h
I
j
L
P
Q
susceptance
capacitance
voltage source
frequency
conductance
h-operator
current
j-operator
inductance
active power
reactive power
[siemens, S]
[farads, F]
[volts, V]
[hertz, Hz]
[siemens, S]
[1Ð120°]
[amps, A]
[1Ð90°]
[henrys, H]
[watts, W]
[VAreactive, VArs]
Q
R
S
t
V
W
X
Y
Z
f
w
quality factor
resistance
apparent power
time
voltage drop
energy
reactance
admittance
impedance
phase angle
angular frequency
[number]
[ohms, W]
[volt-amps, VA]
[seconds, s]
[volts, V]
[joules, J]
[ohms, W]
[siemens, S]
[ohms, W]
[degrees, °]
[rad/sec]

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4 Comments


  1. Mon Mon Min Eain
    Aug 15, 2018

    Thank you so much.


  2. Edward
    Dec 09, 2015

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    Jul 25, 2015

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    Feb 16, 2012

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