2. • Transformers are capable receiving AC power at one
voltage and delevring it at another voltage; in this way,
they hope achieve better transmission effeciency while
transferring the power over longer distances.
• In this tutorial, we will go through the working and
construction of a 3-phase transformer by starting from
its simplest form.
3. • The basic working principal of a transformer is easy,
ectromagnetic induction. According to this principal, a
varying magnetic flux associated with a loop will induce
an electromotive force accross it.
• Such a fluctuating magnetic field can easily be produced
by a coil. A current carrying conductor produces a
magnetic field around it, the magnetic field produced by
a coil will be as shown:
4. • With the fluctuating nature of the alternating current,
the magnetic field associated with the coil will also
fluctuate.
5. • This magnetic flux can be effectively linked to a
secondary winding with the help of a core made up of
ferromagnetic material.
6. • This fluctuating magnetic field will induce an e.m.f in the
secondary coils due to electromagnetic induction.
• Since the turns are arranged in a series, the not e.m.f
induced across the winding will be the sum of the
individual e.m.fs induced in each turn.
7.
8. • Since the same magnetic flux is passing through the
primary and the secondary coils, the e.m.f per turn for
both the primary and the secondary coils will be the
same. The e.m.f per turn for the primary coil is related
to the applied input voltage as shown:
• As a result, the induced e.m.f at the secondary coil is
expressed as follows:
9.
10. • This simply means that with a few turns in the
secondary than in the primary, one can low in the
voltage. For the reverse case, one can increase the
voltage.
11. • But since energy in conserved, the primary and
secondary current have to obey the following
relationship:
• 3-phase transformers use 3 such single phase
transformers, but with a slightly different coil
configuration.
12.
13. • Here, the primary and secondary coils set concentrically.
2 more such windings are employed in a 3-phase
transformer, transformers with high power ratings
generally employ a special kind of windings, known as a
Disc Type Winding.
14.
15. • Where separated disk windings are connected in series
through outer and inner cross-overs, the low voltage
windings are connected in a delta configuration, and
the high voltage windings are connected in a star
configuration.
16. • Thus, the line voltage further rises to road 3 times at
high voltage side, this also means that from a 3-phase
start-up transformer , we can drive 4 output wires: 3-
phase power wires and 1 neutral.
• High voltage insulated bushings are required to bring
out the electrical energy, the core of the transformer is
made of thin insulated steel lamination.
17. • Such steel laminations are stacked together as shown to
form a 3-phase lames, the purpose of thin lamination is
to reduce energy loss due to eddy current formation.
• The low voltage windings are usually set in the core,
various kinds of energy loss happen while transferring
power from the primary to the secondary coil. All these
energy losses are dissipated as heat.
18. • So usually the transformer is immersed in a cooling oil to
dissipate the heat, the oil dissipates the heat via a
neutral convection. Oil in the tank will expand as it
absorbes the heat, a conserved added tank ups to
accomodate for this volume change.
• Thank you.
