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Reactance (X) and Susceptance (B)
In AC circuit analysis, reactance is represented by the capital letter “X” which
is the imaginary a part of complex impedance. Reactance is the opposition of
a circuit element to a change in the current or voltage, due to that element's
inductance or capacitance which is similar to the opposition of resistance to
current in a DC circuit. In an AC circuit (e.g. a series RLC circuit) inductance
and capacitance may oppose current and are named reactance measured in
units of Ohm (Ω).
In electrical engineering, susceptance (B) is the imaginary part of admittance.
The inverse of admittance is impedance, and the real part of admittance is
conductance. The latter is the reciprocal of impedance (B=1/X) and is meas-
ured in units of Siemens (S).
⚫
Reactance (X)
:
Measure Type
：
Series mode→Xs (Reactance is measuring by series
mode only.)
Relevant Equations
：
(
)
(
)
sin
Z
sin
1
2
2
2
2
s
Z
X
X
R
RX
Z
X
R
Z
B
X
s
p
=
+
=
+
=
=
=
⚫
Susceptance (B)
:
Measure Type
：
parallel mode→Bp (Reactance is measuring by parallel
mode only.)
Relevant Equations
：
