2. Transformer
An A.C. device used to change high voltage low
current A.C. into low voltage high current A.C. and
vice-versa without changing the frequency
In brief,
1. Transfers electric power from one circuit to another
2. It does so without a change of frequency
3. It accomplishes this by electromagnetic induction
4. Where the two electric circuits are in mutual
inductive influence of each other.
3. Principle of operation
It is based on principle of
MUTUAL INDUCTION.
According to which an
e.m.f. is induced in a coil
when current in the
neighbouring coil changes.
4. Constructional detail : Shell type
• Windings are wrapped around the center leg of a
laminated core.
6. Working of a transformer
1. When current in the
primary coil changes being
alternating in nature, a
changing magnetic field is
produced
2. This changing magnetic
field gets associated with
the secondary through the
soft iron core
3. Hence magnetic flux linked
with the secondary coil
changes.
4. Which induces e.m.f. in the
secondary.
7. Three-Phase Transformers
Construction
• A three-phase transformer is constructed by
winding three single-phase transformers on a
single core.
• Three-phase transformers are connected in
either wye or delta configurations.
8.
9.
10.
11.
12. PARTS OF TRANSFORMER
• MAIN TANK
• CONSERVATOR
• EXPLOSION VENT
• LIFTING LUGS
• AIR RELEASE PLUG
• OIL LEVEL INDICATOR
• TAP CHANGER
• WHEELS
• HV/LV BUSHINGS
• OIL FILLING PLUG
• DRAIN PLUG
• CABLE BOX
13.
14. (i). Oil
The oil helps cool the transformer. Because it also provides part
of the electrical insulation between internal live parts,
transformer oil must remain stable at high temperatures for an
extended period. To improve cooling of large power
transformers, the oil-filled tank may have external radiators
through which the oil circulates by natural convection.
(ii). Conservator
The transformer conservator acts as a barrier to separate
undesirable elements in the atmosphere, such as water vapor,
nitrogen, ozone and oxygen, from transformer oil within a
conservator. This barrier also reduces condensation and
oxidation inside the transformer and suppresses gas bubble
formation in the transformer oil.
15. (ii) Breather
a) The plug at the end of the breather pipe is to be
removed and breather fitted on to the pipe along with the fly
nut.
b) It is necessary before fitting the breather to observe
the color of the silica-gel. If necessary, the breather should
be opened and the silica-gel properly dried up so that its
color is perfectly bluish.
c) The chamber at the bottom of the breather should be
filled in with dry transformer oil up to the level marked.
(iv) explosion vent
In case an equalizer pipe connection is provided, the
valve in the pipe should be kept in open position before the
transformer is energized.
16. (v)shut off valve
This should always be in fully open position while the
transformer is being energized.
(vi) Transformer tank
a) Open the air release device on the inspection cover and
also on the tank cover to ensure that there is no air trapped
inside the tank.
b) Gently open the nuts at the bottom of each HV bushings
one by one and shake the stud gently until oil starts coming
down. Then tighten the nuts properly. All bushings should be
kept clean.
18. DISTRIBUTION TRANSFORMER
• TRANSFORMER WHICH IS USED FOR THE
PURPOSE OF DISTRIBUTION OF POWER.
• 11KV/433V is the standard voltage rating.
• STANDARD KVA ratings are
25,63,100,160,200,250,315,400,500,630,750 ,
1000,1250,500,2000,2500 KVA.
IS-2026 is the NATIONAL IS STANDARD.
19. Power transformer
• Power transformer construction like as three phase
distribution transformer. But it bigger in size than
three phase distributed transformer. we construct the
3150 KVA power transformer. it is use to step down
the voltage. It step down voltage is 33/11KV.
• The winding connection of power transformer either
star or delta connection.
20.
21. .LOSSES IN TRANSFORMER
All transformers have copper and core losses, and flux
leakage. Copper loss is ohmic power lost in the primary and
secondary windings of a transformer due to the ohmic resistance
of the windings. Copper loss, in watts, may be found using the
following equation
Copper Loss = IP
2 RP+ IS
2 RS
Core losses are caused by two factors: hysteresis and
eddy current losses. Hysteresis loss is that energy lost by
reversing the magnetic field in the core as the magnetizing
AC rises and falls and reverses direction. Eddy current loss is
a result of induced currents circulating in the iron core.
22. TRANSFORMER REGULATION
Loading changes the output voltage of a transformer.
Transformer regulation is the measure of such a deviation.
Definition of % Regulation
{ ( Vno-load -V load )/V load }*100 %
Vno-load =RMS voltage across the load terminals without
load
V load = RMS voltage across the load terminals with a
specified load.
23. %100
in
out
P
P
%100
lossout
out
PP
P
. EFFICIENCY OF TRANSFORMER
Transformer efficiency is defined as (applies to motors,
generators and transformers):
All day efficiency
All day efficiency is of 24 hour.
hours)24(
kWhinInput
kWhinoutput
in wattsinput
in wattsputout
efficiencycommercialordinary
day forall
24. Applications of Transformers
• Transformers have many applications in power
transmission and electronics:
• They may be used to minimise energy losses
due to voltage drop in transmitting electricity over
long distances.
• They match loads with internal resistance so that
there is maximum power transfer.
• They couple signals between electronic stages.
