Working and construction of single phase transformer is explained in this presentation. specially for small power and power frequency transformers.

1. Electrical Transformer

2. Electrical Transformer
• Transformer is an electromagnetic static devise in which input is in the form of
electrical energy and output is also in electrical form as shown
• Input and output both must be alternating type
• The main function of it to change level of voltage and current
Fig. 1
Block diagram

3. Types
1) Step Up transformer:-
• It increases the level of voltage i.e. input voltage is low and output voltage
becomes high
• However the level of current get reduced in same proportion i.e. input current is
high and output current is low.
• But power and frequency remain unchanged.
Block diagram
Fig.3
Block diagram

4. Types
2) Step-Down transformer:-
• It decreases the level of voltage i.e. input voltage is high and output voltage
becomes low.
• However the level of current get increased in same proportion i.e. input current is
less and output current is more.
• But power and frequency remain unchanged.
Block diagram
Fig.3
Block diagram

5. How it works(working principle)
• It works on the principle of “electromagnetic induction”.
For example: if we apply a direct voltage across an electric conductor a current flow
through it in one direction as shown and a magnetic field get established around the
conductor.

6. How it works(working principle)
Dynamically induced EMF: If another peace of wire comes in the vicinity of this field an
electromotive force (EMF) get induced in the piece of wire which we can experience form
deflection in needle of a galvanometer. After some time deflection becomes zero as both
conductors are stationary and means there is no relative movement between them. This
is known as dynamically induced EMF.

7. How it works(working principle)
Statically induced EMF: Further we can also experience that EMF is again induced in the
second conductor when we remove battery this is because of reduction of flux density
around the first conductor, and second conductor try to appose this change in flux. EMF
induced in second conductor this time has opposite direction there galvanometer show
opposite deflection as current flows in opposite direction. Same phenomenon happens
when we connect battery again, as both conductors are stationary this phenomenon is
known as statically educed EMF.
Transformer works only on Alternating
Current
From above discussion it is clear that if
conductors are stationary change in
magnetic field is mandatory for induction
process.

8. Methods to Improve Electro-Magnetic Coupling
1) By using coils on both side instead of using single wire this results increase of flux.
2) By using a magnetic core between the coils which gives law reluctance path to the flux
and improve magnetic coupling between the coils

9. • As you can see here in this case coil of left side or we can call it primary coil has lesser
numbers of turns than the coil on right side or we can call it secondary coil and the
transformer call as step up transformer.
• In this case voltage which induced on secondary coil VOUT than voltage which is applied
VIN on the primary coil, whereas the current get reduced as Power has to remain
constant.

10. • Similarly when primary coil has more number of turns then secondary coil the
transformer is called as Step Down Transformer, and the voltage induced on secondary
side Vout is less than the applied voltage Vin on primary side.

11. • Core which is practically used in a transformer is actually not a solid core, it is made up
of number of thin metal sheets called laminations. This type of construction is used to
reduce Eddy Current Loss, which occurs inside the core when it carries changing or
alternating flux.

12. •As core is used to provide a low reluctant path to the magnetic flux, but the core is
subjected to circulating electric currents, these circulating currents called Eddy Current,
produced heating and energy losses within the core, results in decreasing the
transformers efficiency. These circulating current is produced mainly due to EMF induced
in the iron core.
• As it is constantly being subjected to the changing magnetic field, setup by the external
sinusoidal supply voltage Vin
•To reduce these unwanted power losses thin steel laminations are used to construct the
transformer core.
CORE

13. •Laminations are made up of highly permeable material i.e. silicon steel .
• These laminations are assembled together to build a solid core.
•The resistivity of steel sheet itself is high reducing the EDY current by making the
laminations very thin.
Thin lamination

14. •The thickness of these laminations are vary between 0.25mm-0.5mm and as steel is
conductor so laminations are electrically insulated from each other by a very thin coating
of insulating Varnish or by the use of an oxide layer of the surface.
Coated sheet

15. •The problem with the construction which is so far discussed here is that the two
windings are well separated from each other and there is considerable reduction of
magnetic coupling and hence the efficiency of transformer, this disadvantage is overcome
by using constructing core like this shown in picture
• in which the two windings are bring close to each other thereby improve magnetic
coupling between them.

16. •So this is about the Single Phase Electrical Transformer
• You can watch video of this Presentation at https://youtu.be/U3CubKnkO4c
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