The summarised slides notes of the topic of Transformer

1. TRANSFORMER
Email; arnoldvalaro@gmail.com

2. Transformer
•The device that changes voltage
from one level to another level.
•The change can be from higher
voltage to lower voltage or
lower voltage to higher voltage.

3. How does transformer
work

4. How does transformer
work
•If a.c. flows through the
primary coil, a.c magnetic field
is produced.
•This alternating current
magnetic fields cuts the
secondary coil.

5. How does transformer
work
•If a.c. flows through the
primary coil, alternating
magnetic field is produced.
•This alternating magnetic fields
cuts the secondary coil and
induces emf in the secondary.

6. How does transformer
work
•This process of inducing e.m.f
in the coil of wire by changing
current is called mutual
inductance.

7. Types of Transformers
•There are two main types of
transformers and these are;
a. step-up transformer
b. Step-down transformer

8. a. Step-up transformer
•This changes low voltage to
higher voltage or steps up
voltage.
•The secondary coil has more
number of turns than primary
coil.

9. a. Step-up transformer

10. b. Step-down transformer
•This changes high voltage to
lower voltage or steps up
voltage.
•The secondary coil has less
number of turns than primary
coil.

11. b. Step-down transformer

12. Formula in transformers

13. Formula of Transformer.

14. Formula of Transformer.

15. Example
 An alternating e.m.f of 240V
alternating current power supply.
The primary coil has 1000 turns
and 4000 turns on its secondary
coil. The secondary coil is 0.2A

16. Example
Calculate;
a. Secondary e.m.f
b. Primary current
c. Power input

17. Example
c. Efficiency
d. Comment on the answer to (d)

18. a. Secondary e.m.f

19. b. Primary current

20. c. Power input

21. c. Power input

22. d. Efficiency

23. e. Comment on answer of d
This is an ideal transformer

24. Exercise
1. Transformer has 66 turns in
primary coil and 660turns in
secondary coil. The voltage in
the primary circuit is 240V.
Calculate secondary coil voltage?

25. Exercise
 The current in the primary coil
of a transformer is 5A and the
voltage in primary coil is 220V.
The voltage on the secondary
coil is 10V.

26. Power Losses In Transformer
a. Resistance of windings
b. Eddy currents
c. Self demagnetised
d. Leakage of field lines

27. a. Resistance of windings
As current flows in the coils,
wires heat up and energy is lost
inform of heat.
The heat production in the
transformer is due to higher
resistance.

28. b. Eddy Currents
The magnetic field in the
transformer changes inducing
eddy currents.
This heats up the core and
energy is lost inform of heat in
a transformer.

29. c. Hysteresis losses
The magnetization and
demagnetization of the core
requires energy.
This energy heats up the core
and is lost as heat energy.

30. d. Magnetic Leakage/Flux
Not all magnetic field lines
from the primary coil may reach
the secondary coil.
The lost magnetic field lines
leads to lost of power in a
transformer

31. Minimize Power Losses
a. Resistance of windings
b. Eddy currents
c. Hysteresis losses
d. Magnetic Leakage/Flux

32. a. Resistance of windings
To minimize this loss of energy
thick copper wires of low
resistance are used.
The thick copper wires have
low resistance hence minimizing
heat loss .

33. b. Eddy Currents
 To minimize the heat loss the
core is laminated and insulated.
This reduces the eddy currents
induced between laminations.

34. b. Hysteresis losses
•To minimize this, the core is
made up soft magnetic
material(soft iron).
•This is easy to magnetize and
demagnetize, reducing heat
losses.

35. d. Magnetic Leakage/Flux
 To minimize this the core is
designed in such way that all the
magnetic field lines from the
primary coil should reach the
secondary coil.

36. Notes
 To completely reduce heat
losses in a transformer is
impossible.
The large transformer uses oil
to absorb heat, heat reducing
overheating.