2. ( The Heart Of Alternating Current System )
What is Transformer ?
Structure& Working principle ?
Construction of Transformer ?
Losses In transformer?
Types of Transformer?
Uses & Applications of transformer
3. Device that converts an alternating
(A/C) current of a certain voltage to
an alternating current of different
voltage,
without change of frequency, by
electromagnetic induction is Known
as Transformer
4. The main principle of operation of a
transformer is mutual inductance between
two circuits which is linked by a common
magnetic flux. A basic transformer consists
of two coils that are electrically separate and
inductive, but are magnetically linked through
a path of reluctance. The working principle of
the transformer can be understood from the
figure below.
5. A transformer consists of two windings interlinked
by a mutual magnetic field.
◦ Primary winding – energized by connecting it to
an input source
◦ Secondary winding – winding to which an
electrical load is connected and from which
output energy is drawn.
Primary winding Secondary winding
6. ΦP = net flux in window of primary ΦS = net
flux in window of secondary
Φlp = leakage flux of primary Φls = leakage
flux of secondary
ΦM = mutual flux
ΦP = ΦM + Φlp
ΦS = ΦM – Φls
7. The losses that occur in transformers have to be accounted for in any
accurate model of transformer behavior.
1. Copper (I2R) losses. Copper losses are the resistive heating losses in the
primary and secondary windings of the transformer. They are proportional
to the square of the current in the windings.
2. Eddy current losses. Eddy current losses are resistive heating losses in
the core of the transformer. They are proportional to the square of the
voltage applied to the transformer.
3. Hysteresis losses. Hysteresis losses are associated with the rearrangement
of the magnetic domains in the core during each half-cycle. They are a
complex, nonlinear function of the voltage applied to the transformer.
4. Leakage flux. The fluxes which escape the core and pass through only
one of the transformer windings are leakage fluxes. These escaped fluxes
produce a self-inductance in the primary and secondary coils, and the
effects of this inductance must be accounted for.
8.
9. voltage across the primary coil
voltage across the secondary coil
number of turns on primary
number of turns on secondary
V
V
N
N
p
s
p
s
Where Vp = primary voltage
Vs = secondary voltage
Np= Number of turns in primary coil
Ns = Number of turns in a secondary coil.
10. A step-up transformer increases the
voltage - there are more turns on the
secondary than on the primary.
A step-down transformer decreases the
voltage - there are fewer turns on the
secondary than on the primary.
To step up the voltage by a factor of 10,
there must be 10 times as many turns
on the secondary coil as on the primary.
The turns ratio tells us the factor by
which the voltage will be changed.
12. Autotransformers
Autotransformers are different from
traditional transformers because
autotransformers share a common winding.
Auto transformer is kind of electrical
transformer where primary and secondary
shares same common single winding.
13. Autotransformer Transformer
Lower leakage More leakage
Lower losses More losses
Lower magnetizing current More Magnetizing current
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