Inductors: functions and parts

2. CONTENTS
What is an inductor?
History of it
Uses
Types
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3. INDUCTOR
An inductor, also called a coil,
choke, or reactor, is a passive two-
terminal electrical component that
stores energy in a magnetic field
when electric current flows through
it.
The inductor is an electrical
component used to introduce
inductance into a circuit which
opposes the change of current flow,
both magnitude and direction, and
that even a straight piece of
conductive wire can have some
amount of inductance in it.
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The schematic symbol for a inductor is that
of a coil of wire so therefore, a coil of wire
can also be called an Inductor. Inductors
usually are categorised according to the type
of inner core they are wound around, for
example, hollow core (free air), solid iron
core or soft ferrite core with the different core
types being distinguished by adding
continuous or dotted parallel lines next to the
wire coil as shown below

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The current, that flows through an inductor produces a magnetic flux that is
proportional to it. But unlike a Capacitor which oppose a change of voltage across
their plates, an inductor opposes the rate of change of current flowing through it due
to the build up of self-induced energy within its magnetic field.
In other words, inductors resist or oppose changes of current but will easily pass a
steady state DC current. This ability of an inductor to resist changes in current and
which also relates current, I with its magnetic flux linkage, NΦ as a constant of
proportionality is called Inductance which is given the symbol L with units of Henry,
(H) after Joseph Henry.

7. Inductance was first found by Faraday in a
simple yet strange way: he wrapped a paper
cylinder with wire, attached the ends of the wire to
a galvanometer (a device used to measure electric
current), and moved a magnet in and out of the
cylinder. The galvanometer reacted to this,
revealing the production of a small current.

8. Shortly after this discovery, Reverend Nicholas
Calland of Ireland invented the inductor coil. The
earliest version of the inductor consisted of a coil
with two terminals at the ends which stored
energy inside a magnetic field when a current
was introduced.

9. Inductors are primarily used in electrical power and electronic devices for these major
purposes: Choking, blocking, attenuating, or filtering/smoothing high frequency noise in
electrical circuits. Storing and transferring energy in power converters (dc-dc or ac-dc)
Different Types of Inductors
Air Core Inductor Laminated Steel Core Inductor
Iron Core Inductor Iron Powder Core Inductor
Ferrite Core Inductor Ceramic Core Inductor
Soft ferrite
Hard ferrite

10. AIR CORE
INDUCTOR
The commonly seen inductor, with a simple
winding, is this Air-Core Inductor. This has
nothing but air as the core material. Air
core inductor uses any non-magnetic
material like plastic and ceramic as core to
reduce the core losses i.e. eddy current
and stray losses, especially when the
operating frequency is very high. However,
the use of a non-magnetic core also
decreases its inductance.
Air Core Inductors are used for constructing
RF tuning coils. They are also used in filter
circuits, snubber circuits, and high-
frequency applications including TV and
radio receivers.
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11. IRON CORE
INDUCTOR
These Inductors have Ferromagnetic
materials, such as ferrite or iron, as the
core material. The usage of such core
materials helps in the increase of
inductance, due to their high magnetic
permeability. These inductors have high
power value but are limited in high-
frequency capacity.
In the areas where low space inductors are
in need then these iron core inductors are
the best option. These Inductors are also
used in the manufacture of a few types of
transformers. Iron core inductors are
applicable in audio equipment. When
compared with other core indicators these
have very limited applications.
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12. FERRITE CORE
INDUCTOR
These types of inductors use ferrite
cores. Ferrite is a material with high
magnetic permeability made from the
mixture of iron oxide (ferric oxide,
Fe2O3) and a small percentage of other
metals such as nickel, zinc, barium, etc.
The ferrite core has very low electrical
conductivity which reduces the eddy
current in the core, resulting in very low
eddy current loss at high frequency.
Hence they can be used in high-
frequency applications. They also offer
advantages of decreased cost.
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13. THERE ARE TWO TYPES OF FERRITES I.E. HARD
FERRITES AND SOFT FERRITES.
The Hard ferrites are also called permanent magnets. These will keep
the polarity of the magnetization even after removing the magnetic field.
They are not used in inductors because of their high hysteresis loss.
The Soft ferrites can reverse the polarity of their magnetization without
any particular amount of energy needed to reverse the magnetic polarity.
Their magnetization changes easily and are good conductors of the
magnetic field. Thus they are used in transformers and inductors.
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14. LAMINATED
STEEL CORE
INDUCTOR
In such types of inductors, the core
is laminated which means that it is
made up of a bunch of thin sheets
placed on top of each other in a
tight form. The sheets are coated
with insulation to increase their
electrical resistance and prevent
eddy current flow between them.
Therefore the eddy current loss in
laminated core inductors decreases
significantly. They are used in high-
power applications.
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15. IRON POWDER
CORE
INDUCTOR
These are formed from very fine
particles with insulated particles
of highly pure iron powder. This
type of inductor contains nearly
100% iron only. It gives us a
solid-looking core when this iron
power is compressed under very
high pressure and mixed with a
binder such as epoxy or
phenolic. By this action iron
powder forms like a magnetic
solid structure which consists of
a distributed air gap.
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16. CERAMIC
CORE
INDUCTOR
Ceramic is a non-magnetic
material just like air. Ceramic
cores are used to provide a
shape for the coil and a structure
for its terminals to sit upon. As it
is a non-magnetic material, it has
low magnetic permeability and
low inductance. But it provides a
reduction in the core losses. It is
mostly available in SMD
packaging and is used in
applications where low core
losses, High Q, and low
inductance are required.
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