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ENABLING OBJECTIVES (Cont.) | Up
Electrical Science Volume 3 of 4 | Next
Voltage and Current Phase Relationships in an Inductive Circuit |
Basic AC Reactive Components
INDUCTANCE
INDUCTANCE
Any device relying on magnetism or magnetic fields to operate is a
form of inductor. Motors, generators, transformers, and coils are
inductors. The use of an inductor in a circuit can cause current and
voltage to become out-of-phase and inefficient unless corrected.
EO 1.1
DESCRIBE inductive reactance (XL).
EO 1.2
Given the operation frequency (f) and the value of
inductance (L), CALCULATE the inductive reactance
(XL) of a simple circuit.
EO 1.3
DESCRIBE the effect of the phase relationship between
current and voltage in an inductive circuit.
EO 1.4
DRAW a simple phasor diagram representing AC
current (I) and voltage (E) in an inductive circuit.
Inductive Reactance
In an inductive AC circuit, the current is continually changing and is continuously inducing an
EMF. Because this EMF opposes the continuous change in the flowing current, its effect is
measured in ohms. This opposition of the inductance to the flow of an alternating current is
called inductive reactance (XL). Equation (8-1) is the mathematical representation of the current
flowing in a circuit that contains only inductive reactance.
(8-1)
I
E
XL
where
I = effective current (A)
XL = inductive reactance (W)
E = effective voltage across the reactance (V)
The value of XL in any circuit is dependent on the inductance of the circuit and on the rate at
which the current is changing through the circuit. This rate of change depends on the frequency
of the applied voltage. Equation (8-2) is the mathematical representation for XL.
(8-2)
XL
2pfL
Rev. 0
Page 1
ES-08
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