Engineering

1. INDUCTORS

2.  Stores energy in the form of magnetic field and
delivers it as and when required.
 Whenever current passes through a conductor, lines
of magnetic flux are generated around it. This
magnetic flux opposes any change in current due to
the induced e.m.f.
 This opposition to the current is known as
inductance and the component producing
inductance is known as inductor.

3. Unit  Henry (H).
Induced e.m.f (electromotive force):
L= inductance in Henry
di/dt = rate of change of current.

4. FACTORS THAT AFFECT INDUCTANCE OF A COIL.
 Number of turns in the coil
 Permeability of the core material.
 Size of core.
Inductance is given by,

5.  Permeability is the measure of the ability of a
material to support the formation of a magnetic field
within itself.

6.  An inductor consist of  copper wire wound around
a core made up of a ferromagnetic material.

8. FERRO MAGNETIC MATERIAL

9. TYPES
 Fixed inductors
⚫ Air core inductors
⚫ Iron core inductors
⚫ Ferrite core inductors
Variable inductors.

10. FIXED INDUCTORS
AIR CORE INDUCTORS
 Former made up of ceramic plastic or
cardboard.

11.  Air will be there inside former.
 It has the least inductance, since in air all magnetic
lines produced by changing current do not link with
every turn of coil, many of them lost in space.

12. HIGH FREQUENCY AIR CORE INDUCTORS

13. IRON – CORE INDUCTOR.
 Copper wire  wound on hallow former
 Core material passes through the former  it forms
closed magnetic path for the magnetic flux.
 So, it donot leak outside of coil.
 Flux line  iron + total flux
 Former  paper or plastic
 Core  silicon steel or ferromagnetic material in
the form of sheets.
 Laminated Sheets  to reduce hysteresis and
eddy current losses.

18.  Iron – core inductors  called choke
 Useful at low frequencies.
 Value  few henries.
 Applications:
⚫ Filter circuit in power supplies.
⚫ Chokes in fluorescent tubes

19.  Eddy current  electric currents induced in
conductors when exposed to a changing magnetic
field.
 Disadvantages:
 enormous increase in hysteresis and eddy current
loss
 Cannot be used for high frequencies.

20. FERRITE CORE INDUCTORS
 For High frequency applications.
 Core  ferrite  an insulator having high
permeability.
 Ferrite  hard, dense ceramics
made of
ferric oxide +metal oxides

21.  Ferrite core  solid and not in laminated sheets
 Because of their high resistivity.
 Value  few μH to few mH.

23. APPLICATIONS
 R.f chokes for supply decoupling purposes.
 Switching regulated type d.c power supplies
 Various types of filters in communication
equipment.

24. VARIABLE INDUCTORS