Transformer:
Transformer is a electromagnet device which transfer power from one circuit to another circuit without any electrical connected.
In transformer two electrical circuit are connected through a magnetic circuit.
In primary winding electrical power is converted into magnetic power and in secondary circuit magnetic power is converted into electrical power.
In power system we use transformer to step up and step down the voltage. But it does not change VA and frequency.
Transformer in Electronic circuit :
In electronic circuit transformer is used as matching device so that maximum power is transferred between source and load.
Working Principle:
The working principle of transformer is based on Faraday’s Law of Mutual Induction or Electromagnetic Induction, which happens between two circuits connected by a mutual magnetic flux.
Construction of Transformer :
The major parts of Transformer are:
Transformer Core :
Core provide minimum reluctance path to magnetic flux.
Core is made up of CRGO steel .(Cold rolled grain oriented silicon steel).
We add 4-5% of silicon in the steel which increase it resistance. So that eddy current and eddy current loss is reduce.
We can't add more than 4-5% of silicon otherwise core become brittle (Mechanically weak).
The steinmetz constant of silicon steel is 1.6 so it also reduce the hysteresis losses.
To reduce the eddy current loss we use laminated silicon steel sheet of thickness 0.35mm(0.3-0.5mm) each lamination is electrically isolated from each other with insulating material.
2. Transformer winding:
We can use cooper material for winding.
In Core Type Transformer concentric winding is used.
Both LV(low voltage) and HV(High voltage) windings are placed at same leg to reduce the leakage flux.
Near to the core we use LV winding so that less amount of insulating material is required.
HV windings are placed outside so that tap changes can be placed on HV winding for fine voltage control.
In Shell Type Transformer interleaved (sandwich) type winding is used in middle leg.
Near to the core we always use LV winding.
On top winding and bottom winding number of turn should be half of middle winding number of turn so that symmetrical forces exist between winding.
# The leakage flux of shell type transformer is lower than core type transformer.
3. Transformer Tank:
Transformer tank is used for mechanical protection of transformer core ,winding and other accessories.
It is made up of cast iron.
To reduce stray loss it should made up of Aluminium.
4. Transformer Oil:
Transformer oil used used for insulation & cooling purpose.
We use mineral oil in transformer.
5. Conservator & Breather:
Conservator tank provide extra space for transformer oil during high load.
We can use Silica gel in breather so that it absorb moisture from atmospheric air.
6. Radiator :
Radiator is used to increase the cooling rate of transformer.
It increase the exposed area to atmosphere which help in cooling.
7. Bushing:
Bushing provides insulator between live conductor and transformer tank.
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