i.

Ch – 3 Magnetic Material
2. Materials that can be magnetized, which are also the ones that are strongly
attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include
the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth
metals, and some naturally occurring minerals such as lodestone.
3. Examples of magnetic substances include iron, nickel, cobalt, stainless steel,
and many rare earth metals. Diamagnetic materials like copper and gold are
weakly repelled by a magnetic field. Paramagnetic materials like calcium and
aluminum are weakly attracted by a magnetic field.

4. H characteristics of magnetic material

5. The B-H curve is usually used to describe the magnetization properties of such
materials by characterizing the permeability , which is defined as: where and
represent the magnetic flux density in tesla (T) and the magnetic field intensity
in ampère per meter (A/m), respectively

6.

7. Ideal And Practical Transformer

8. A transformer is a static electrical machine which is used to transform the
level of alternating voltage, i.e. a transformer increases or decreases the
value of alternating voltage without changing in its frequency.
9. As every electrical machine has some power loss in it, thus depending upon
the losses occur in the transformer, the transformer is of two types viz. −
10. Ideal transformer
11. Practical transformer

12.

13. What is an Ideal Transformer?

14. The theoretical model of a real transformer without losses is known as ideal
transformer. In other words, an ideal transformer is an imaginary
transformer for which the energy losses are zero.
15. An ideal transformer has the following characteristics −

16. The primary and secondary windings have negligible (or zero) resistance.
17. No leakage flux, i.e., whole of the flux is confined to the magnetic circuit.
18. The magnetic core has infinite permeability, thus negligible MMF is require
to establish flux in the core.
19. There are no losses due winding resistances, hysteresis and eddy currents.
Hence, the efficiency is 100%.
20. It is important to note that an ideal transformer does not exist in real life,
which means it is a hypothetical and cannot be realized practically.

21. Difference between Ideal Transformer and Practical

Transformer
22. Basis of 23. Ideal Transformer 24. Practical Transformer
Difference
 27. A practical transformer is
26. An ideal transformer is a
25. Definition theoretical model of transformer one which has energy
with no energy losses in it. losses in it.

29. For an ideal transformer, the 30. A practical transformer

28. Core losses core losses (i.e. hysteresis loss has finite core losses.
and eddy current loss) are zero.
33. There is finite copper loss
31. Copper 32. The copper loss (or I2R loss) in
in case of a practical
losses an ideal transformer is zero.
transformer.
36. A practical transformer
35. The efficiency of an ideal
34. Efficiency always has efficiency less
transformer is equal to 100%.
than 100%.
38. The efficiency of an ideal 39. The efficiency of a
transformer is always 100% practical transformer
37. Dependency
and does not depend on any depends upon the power
of efficiency
parameter. factor and loading of the
transformer.
41. The resistance of the windings 42. The windings of a
40. Winding of an ideal transformer is zero practical transformer
resistance (or negligibly small). have some finite
resistance.
45. A practical transformer
43. Ohmic 44. In an ideal transformer, there is
has some Ohmic
resistance no Ohmic resistance drop due
resistance drop due to
drop to zero winding resistance.
winding resistance
47. The windings of an ideal 48. The windings of a
transformer are purely inductive. practical transformer are
46. Nature of
not purely inductive, they
winding coils
also have a finite
resistance.
50. There is no leakage flux in an 51. There is a flux leakage in
ideal transformer, which means a practical transformer.
49. Magnetic
all the flux produced by primary
flux leakage
winding gets fully linked to the
secondary winding.
52. Basis of 53. Ideal Transformer 54. Practical Transformer
Difference
55. Permeability 56. The permeability of core of an 57. The core of a
 ideal transformer is considered practical
infinite. transformer
of core
has finite
permeability.
59. An ideal transformer is
60. All the transformers exist
theoretical model of the
58. Existence in real world are the
transformer, hence it does not
practical transformers.
exist in real life.
62. An ideal transformer is only 63. The practical
used for analyzing the transformer is used in
61. Applications transformer circuits. practice to step-up or
step-down the voltage
levels.

64. Equivalent Circuit Of Transformer

65. Resistances and reactances of transformer, which are described above,
can be imagined separately from the windings (as shown in the figure
below). Hence, the function of windings, thereafter, will only be the
transforming the voltage.
66.

67. The no load current I0 is divided into, pure inductance X0 (taking

magnetizing components Iμ) and non induction resistance R0 (taking
working component Iw) which are connected into parallel across the
primary.
68. Losses In Transformers
69. An ideal transformer is very efficient, they don’t have energy losses. It means
power supplied to the transformer’s input terminal must be equivalent to the
power supplied to the transformer’s output one. So the input power and output
power in an ideal transformer are equal including zero energy losses.

70.

1.Core Losses Or Iron Losses

71. Eddy current loss and hysteresis loss depend on the
magnetic properties of the material used for the
construction of the core. So, these losses are also known as
core losses or iron losses.

72. Hysteresis loss in transformer: The reason is the

reversal of magnetization in the transformer core. This loss
depends on the volume and grade of the iron, frequency of
magnetic reversals and value of flux density. We have the
Steinmetz formula:
 a. Wh= ηBmax1.6fV (watts)

Where, η = Steinmetz hysteresis constant

V = volume of the core in m3

• Eddy current loss in transformer: The AC current is

supplied to the primary winding which sets up alternating
magnetizing flux in the transformer. When this flux flow to a
secondary winding, it produces induced emf in it. But some
part of this flux also gets linked with other conducting parts
such as steel core or iron body or the transformer, which will
result in induced emf in those parts, causing small circulating
current in them. This current is called as eddy current. Due to
the current, some energy will be dissipated in the form of
heat.

2. Copper Loss
The ohmic resistance of the transformer windings creates
copper loss. The copper loss for the primary winding is I12R1
and for the secondary winding is I22R2. Where, I1 and I2 are
current in primary and secondary winding respectively, R1
and R2 are the resistances of primary and secondary winding
respectively. We can see that Cu loss is proportional to
square of the current, and current depends on the load. So
that copper loss in transformer varies with the load

3. Stray Loss
The reason for the types of loss is the occurrence of the
leakage field. When compared with copper and iron losses,
the percentage of stray losses are less, so these losses can
be neglected.
4. Dielectric Loss
The oil of the transformer is the reason for this loss. Oil in
transformer is an insulating material. When the oil in the
transformer gets deteriorates then the transformer’s
efficiency will be affected.