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transformer is an electrical device that
transfers electrical energy between two or
more circuits through electromagnetic
induction. Electromagnetic induction
produces an electromotive force within a
conductor which is exposed to time
varying magnetic fields. Transformers are
used to increase or decrease the alternating
voltages in electric power applications.
For simplification or approximation purposes, it is
very common to analyze the transformer as an
ideal transformer model as presented in the two
images. An ideal transformer is a
theoretical, linear transformer that is lossless and
perfectly coupled; that is, there are no energy
losses and flux is completely confined within
the magnetic core. Perfect coupling implies
infinitely high core magnetic permeability and
winding inductances and zero net magnetomotive
force.[
A dot convention is often used in transformer circuit diagrams,
nameplates or terminal markings to define the relative polarity
of transformer windings. Positively increasing instantaneous
current entering the primary winding's dot end induces
positive polarity voltage at the secondary winding's dot end.
The ideal transformer model neglects the following
basic linear aspects in real transformers.
Core losses, collectively called magnetizing current
losses, consist of
Hysteresis losses due to nonlinear application of the
voltage applied in the transformer core, and
Eddy current losses due to joule heating in the core
that are proportional to the square of the transformer's
applied voltage.
he EMF of a transformer at a given flux density increases
with frequency.[23] By operating at higher frequencies,
transformers can be physically more compact because a
given core is able to transfer more power without reaching
saturation and fewer turns are needed to achieve the same
impedance. However, properties such as core loss and
conductor skin effect also increase with frequency. Aircraft
and military equipment employ 400 Hz power supplies
which reduce core and winding weight.[35] Conversely,
frequencies used for some railway electrification systems
were much lower (e.g. 16.7 Hz and 25 Hz) than normal
utility frequencies (50–60 Hz) for historical reasons
concerned mainly with the limitations of early electric
traction motors. Consequently, the transformers used to
step-down the high overhead line voltages (e.g. 15 kV)
were much larger and heavier for the same power rating
than those required for the higher frequencies.
Real transformer energy losses are
dominated by winding resistance joule and
core losses. Transformers' efficiency tends
to improve with increasing transformer
capacity. The efficiency of typical
distribution transformers is between about
98 and 99 percent
Current flowing through a winding's conductor
causes joule heating. As frequency increases, skin
effect and proximity effect causes the winding's
resistance and, hence, losses to increase.
Materials are also good conductors and a core
made from such a material also constitutes a
single short-circuited turn throughout its entire
length. Eddy currents therefore circulate within
the core in a plane normal to the flux, and are
responsible for resistive heating of the core
material. The eddy current loss is a complex
function of the square of supply frequency and
inverse square of the material thickness.[40] Eddy
current losses can be reduced by making the core
of a stack of plates electrically insulated from each
other, rather than a solid block; all transformers
operating at low frequencies use laminated or
similar cores.
Transformers can be classified in many ways, such as the
following:
Duty of a transformer: Continuous, short-time, intermittent,
periodic, varying.
Voltage class: From a few volts to hundreds of kilovolts.
Cooling type: Dry and liquid-immersed – self-cooled, forced air-
cooled; liquid-immersed – forced oil-cooled, water-cooled.
Circuit application: Such as power supply, impedance matching,
output voltage and current stabilizer or circuit isolation.
Basic magnetic form: Core form, shell form.
Constant-potential transformer descriptor:
Electromagnetic induction, the principle of the
operation of the transformer, was discovered
independently by Michael Faraday in 1831, Joseph
Henry in 1832, and others.[97][98][99][100]The relationship
between EMF and magnetic flux is an equation now
known as Faraday's law of induction:
Transformer

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Transformer

  • 1.
  • 2. transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. Electromagnetic induction produces an electromotive force within a conductor which is exposed to time varying magnetic fields. Transformers are used to increase or decrease the alternating voltages in electric power applications.
  • 3. For simplification or approximation purposes, it is very common to analyze the transformer as an ideal transformer model as presented in the two images. An ideal transformer is a theoretical, linear transformer that is lossless and perfectly coupled; that is, there are no energy losses and flux is completely confined within the magnetic core. Perfect coupling implies infinitely high core magnetic permeability and winding inductances and zero net magnetomotive force.[
  • 4.
  • 5.
  • 6. A dot convention is often used in transformer circuit diagrams, nameplates or terminal markings to define the relative polarity of transformer windings. Positively increasing instantaneous current entering the primary winding's dot end induces positive polarity voltage at the secondary winding's dot end.
  • 7. The ideal transformer model neglects the following basic linear aspects in real transformers. Core losses, collectively called magnetizing current losses, consist of Hysteresis losses due to nonlinear application of the voltage applied in the transformer core, and Eddy current losses due to joule heating in the core that are proportional to the square of the transformer's applied voltage.
  • 8. he EMF of a transformer at a given flux density increases with frequency.[23] By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance. However, properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 400 Hz power supplies which reduce core and winding weight.[35] Conversely, frequencies used for some railway electrification systems were much lower (e.g. 16.7 Hz and 25 Hz) than normal utility frequencies (50–60 Hz) for historical reasons concerned mainly with the limitations of early electric traction motors. Consequently, the transformers used to step-down the high overhead line voltages (e.g. 15 kV) were much larger and heavier for the same power rating than those required for the higher frequencies.
  • 9. Real transformer energy losses are dominated by winding resistance joule and core losses. Transformers' efficiency tends to improve with increasing transformer capacity. The efficiency of typical distribution transformers is between about 98 and 99 percent
  • 10. Current flowing through a winding's conductor causes joule heating. As frequency increases, skin effect and proximity effect causes the winding's resistance and, hence, losses to increase.
  • 11. Materials are also good conductors and a core made from such a material also constitutes a single short-circuited turn throughout its entire length. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material. The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness.[40] Eddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other, rather than a solid block; all transformers operating at low frequencies use laminated or similar cores.
  • 12. Transformers can be classified in many ways, such as the following: Duty of a transformer: Continuous, short-time, intermittent, periodic, varying. Voltage class: From a few volts to hundreds of kilovolts. Cooling type: Dry and liquid-immersed – self-cooled, forced air- cooled; liquid-immersed – forced oil-cooled, water-cooled. Circuit application: Such as power supply, impedance matching, output voltage and current stabilizer or circuit isolation. Basic magnetic form: Core form, shell form. Constant-potential transformer descriptor:
  • 13. Electromagnetic induction, the principle of the operation of the transformer, was discovered independently by Michael Faraday in 1831, Joseph Henry in 1832, and others.[97][98][99][100]The relationship between EMF and magnetic flux is an equation now known as Faraday's law of induction: