Download An Inductor are passive components that stores

CHAPTER 6
INDUCTORS
& INDUCTANCE
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•
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End of the lessons, students
should be able to ;
Understand inductors and
inductance
types of inductors
Describe the construction of an
inductor.
Understand inductance
equivalent circuits for series
and parallel connections
INTRODUCTION
• GO TO INDUCTOR VIDEO
Inductors
An Inductor are passive components
that stores energy in the form of the
magnetic field.
What is an Inductor?
Current
Flux
i
A coil of wire that can
carry current
Current produces a magnetic field
Energy is stored in the inductor
4
Basic Inductor
Electromagnetic Field - DC
Inductance
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In electromagnetism and electronics, inductance
is the ability of an inductor to store energy in
a magnetic field.
• To add inductance to a circuit, electronic components
called inductors are used, typically consisting of coils of
wire to concentrate the magnetic field and to collect the
induced voltage.
•The unit : henry (H), which is defined as
the production of one volt of counter-emf
in a coil when current has a change of one
ampere per second.
• The symbol : L
• Inductance can be increased by looping
the conductor into a coil which creates a
larger magnetic field.
TYPES OF INDUCTORS :
FIXED INDUCTOR
An inductor whose coils are wound in such
a manner that the turns remain fixed in
position with respect to each other.
SYMBOL :
a) Air core inductors
Inductance value is micro henry or less and usually used in
high frequency. For example, this inductor used as radio
frequency choke to prevent the current radio frequency
(high frequency) of a particular route in the circuit.
b) Iron core-coils
The iron core is laminated iron core coated with a thin
insulator. Inductance value of the iron core is a few
millimeter to several henry. It is used as a low-frequency
filter in the voltage supply circuit. It is also used as a choke
in the circuit of “lampu pendaflour”
(c)Powder iron core inductors and ferrite core inductors
Powder iron core is produced with the appearance of
iron powder covered by insulation. Ferrite core is made
of non-conductive magnetic material. By using powder
iron core or ferrite iron core, the inductance will be
higher and the size can be reduced.
They have three forms, namely a solenoid, toroid and
pot core. Solenoid type 1micro henry inductance value
or less while the pot core and toroid have the
inductance values between a few to a few milli
microhenry.
Normally used in radio tuning circuits.
VARIABLE INDUCTOR
- A coil whose effective inductance can be changed.
- can be constructed by making one of the terminals of
the device a sliding spring contact that can move along
the surface of the coil, increasing or decreasing the
number of turns of the coil included in the circuit.
-An alternative construction method is to use a
moveable magnetic core, which can be slid in or out of
the coil.
- Moving the core farther into the coil increases the
permeability, increasing the inductance.
- Many inductors used in radio applications (usually less
than100 MHz) use adjustable cores in order to tune
such inductors to their desired value, since
manufacturing processes have certain tolerances
(inaccuracy).
- Sometimes such cores for frequencies above
100 MHz are made from highly conductive nonmagnetic material such as aluminum.
- They decrease the inductance because the
magnetic field must bypass them.
L = N2µA / l
L=inductance, N= number of turns
l = core length in meters (m), µ= permeability (H/m)
Basic Construction
-It is basically constructed using a copper wire wrapped
around a core make of ferromagnetic material or just
around the air.
- Using ferromagnetic material help to confine the
magnetic flux within the coil and hence increasing the
inductance of the coil.
A typical toroidal coil
-The copper wire must have good insulation to
that is wrapped
around an iron core
prevent shorting of the wires to one another.
- In some circuitry, there is a need to change or tune the value
of the inductance hence an adjustable core type is used.
- An inductor is usually constructed as a coil of conducting
material, typically copper wire, wrapped around a core either
of air or of ferrous material.
- Core materials with a higher permeability than air confine the
magnetic field closely to the inductor, thereby increasing the
inductance.
TYPES OF INDUCTANCE
EQUIVALENT CIRCUIT CONNECTION
1.SERIES CONNECTION
2.PARALLEL CONNECTION
3.SERIES-PARALLEL CONNECTION
Solution..
Series-parallel inductances