As per the syllabus of Gondwana University Gadchiroli

1. Energy Losses in Transformer

2. Transformer
• It is an electrical device which converts low
alternating voltage to high alternating voltage
and vice-versa.
• The working of transformer is based on principle
of mutual induction between two coils.
• The transformer which converts low a.c. voltage
to high a.c. voltage called step-up transformer
• The transformer which converts high a.c. voltage
to low a.c. voltage called step-down transformer

3. Construction
it consist of two separated insulated coils called as primary and
secondary coils . These coils are wounded upon separated limbs
of core which is made up of thin sheet of laminated soft iron.

4. • The alternating input voltage is applied to
primary coil and output is taken across the
secondary coil.
• In step up transformer
𝑁𝑆 > 𝑁𝑃
• In step down transformer
𝑁𝑆 < 𝑁𝑃

5. • Transformation turn ratio (K)
• K=
𝑉𝑠
𝑉𝑃
=
𝐸𝑠
𝐸𝑃
=
𝑁𝑠
𝑁𝑃
• For step up transformer
• K > 1
• 𝑉
𝑠> 𝑉𝑃
• 𝑁𝑠 > 𝑁𝑝
• For step down transformer
• K < 1
• 𝑉
𝑠< 𝑉𝑃
• 𝑁𝑠 < 𝑁𝑝

6. In practical , the power at input (primary) is
not equal the power at output
(Secondary). Hence there are some losses
in the transformer.

7. • There are four types of losses in
Transformer
• 1)Magnetic Flux Leakage
The magnetic flux created at the
primary is not totally transfer to the
secondary coil. Hence some flux is wasted
in between primary coil & secondary coil.
This loss is minimize by special shape
of iron core.

8. • 2) Copper Loss-
As the primary & secondary coil are made
up of copper wire. When current is passes
through copper wire get heated. Hence some
energy is wasted in heating the copper wire.
This loss can be minimized by using thick
copper wire.

9. • Eddy Current Losses-
When current is posses through the coil it
produces induced emf in the coil. Due to this a
small current is developed in the iron core. This
current is called eddy current. Hence some
energy is wasted in creating Eddy current.
This current is minimized by using
laminated iron core.

10. Hysteresis losss
• Due to current in the primary coil magnetic
field is produces in it. As the AC input cycle is
changes , the direction magnetic field is also
changes . Hence some energy is wasted in
changing the direction of magnetic field.
This loss can be minimized by using a material
having low hysteresis loss

11. Uses of Transformer
1)The stepup & stepdown transformer are used
for increasing and decreasing the AC voltage.
2)The audio frequency transformer are used in
audio communication in the frequency level
20Hz to 20KHz.
3) The radio frequency transformer is used for
radio communication in the frequency range of
50Hz to 20MHz.

12. • 4)Constant current transformer is used for
constant current at output.
• 5) The impedance matching transformer is
used to match the impedance of two circuits.

13. Electromagnetic Induction
• Faraday discovered that whenever the
magnetic flux passing through a circuit
changes, an induced e.m.f. is produced in the
circuit.
• Produced current is called induced current .
• Electromagnetic induction is the phenomenon
of production of induced e.m.f. in the coil,
when the magnetic flux with the coil is
changed.

14. Faraday`s Laws of electromagnetic
Induction
• Whenever the magnetic flux associated with
the coil or circuit changes , an induced e.m.f. is
produced in it.
• The magnitude of induced e.m.f. at any instant
is directly proportional to the rate of change
of magnetic flux link with the circuit.

15.  if dø is the change in the magnetic flux in
time dt , then according to faraday’s law
the induced e.m.f. is given by
e ∝
dø
dt
e = 𝑘
dø
dt
where k is constant of proportionality.

16. Lenz’s Law
• The lenz’s law states that the direction of the
induced e.m.f. is such as to oppose the change
producing it.
• e = −
dø
dt
• Negative sign indicates that enduced e.m.f.
always opposes the change in the magnetic
flux

17. Self Induction
• When a changing current is passes through a
coil , there is a flux linked with the coil.
• Hence an induced e.m.f. is set up in the coil.
• This is called self induction

18. Coefficient of self induction (L)
• When a current I flows through a coil, it produces
a magnetic flux ø , which is proportional to the
current.
• ø ∝ I
• ø = L I ………………..(1)
• Where L is called coefficient of self induction or
self inductance of the coil.
If I = 1 then ø = L
Hence coefficient of self induction is equal to
magnetic flux ,when unit current flows through it.
S.I. Unit of self induction is Henry or H

19. Mutual Induction
• When two coils are placed very close to each
other . Then the magnetic flux due to
changing current in the first coil link with
other coil .
• As a result an induced e.m.f. is produced in
the other coil.
• This phenomenon is called mutual induction.

20. Coefficient of mutual induction (M)
• let 𝐼𝑃 is the current flowing through the coil P at
any time .
• Then magnetic flux ø𝑆 link with the coil S is
proportional to 𝐼𝑃
• ø𝑆 ∝ 𝐼𝑃
• ø𝑆 = 𝑀 𝐼𝑃
• Where M is called coefficient of mutual induction
• S.I. Unit of coefficient of mutual induction is
Henry or H