PRESENTATION ON TRANSFORMER CONSTRUCTION

Presented byRakesh KumarReg. no. 11011752

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 another2. It does so without a change of frequency3. It accomplishes this by electromagnetic induction4. Where the two electric circuits are in mutual

inductive influence of each other.

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.

Constructional detail : Shell type

• Windings are wrapped around the center leg of a laminated core.

Core type

• Windings are wrapped around two sides of a laminated square core.

Working of a transformer1. 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.

Three-Phase TransformersConstruction

• 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.

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

(i). OilThe 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). ConservatorThe 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.

(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.

(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.

Transformer with conservator and breather

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.

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.

.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+ IS2 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.

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 loadV load = RMS voltage across the load terminals with a specified load.

%100in

out

PP

%100

lossout

out

PPP

. EFFICIENCY OF TRANSFORMERTransformer efficiency is defined as (applies to motors, generators and transformers):

All day efficiency All day efficiency is of 24 hour.

hours) 24 (kWhin Input kWhin output

in wattsinput in wattsput out efficiency commercialordinary

day forall

Applications of Transformers

• Transformers have many applications in powertransmission and electronics:• They may be used to minimise energy losses due to voltage drop in transmitting electricity overlong distances.• They match loads with internal resistance so thatthere is maximum power transfer.• They couple signals between electronic stages.