Transformer – Short Theory | Cover Full Chapter
Definition : A transformer is a static device used for transforming power from one circuit to another, through electromagnetic induction, without changing frequency.
Parts of a Transformer :–
- Core : – Use to magnetically connect both windings. Made of silicon steel, it is laminated to reduce eddy current loss. 3% – 5% silicon mix with steel to reduce hysteresis loss.
- Primary Winding :– Connect with electrical power source (AC) to produce magnetic flux. Made of Copper.
- Secondary Winding :– Connected to load , used to induce EMF. Made of copper.
- Tank :– It keep save the core, windings and transformer oil.
- Transformer oil :– Use as coolant, insulator and prevent oxidation. Paraffin type oil is generally use due to easy available.
- Conservator :– Provide space for expansion of transformer oil due to temperature rise.
- Buchholz Relay :- It is a safety device, use to indicate internal faults.Located between Tank and Conservator.
- Breather (with Silica Gel) :– Use to absorb the moisture. When it absorb moisture the colour of silica gel become dark-blue to pink.
- Radiator :– Use to cool the transformer oil.
- Drain Valve :– Use to collect damaged oil.
- Tap Changer :– Only provide for Auto-Transformer to control the secondary power, through changing tap-position.
Test of Transformer :-
- Open Circuit Test / OC Test :- Conducted to find core loss. Low voltage side will connect for testing and high voltage side left open.
- Short Circuit Test / SC Test :– Conducted to find copper loss. High voltage side will connect for testing and low voltage side short-circuited.
- Sumpner Test :– Conducted to determine temperature.
Voltage Regulation : If voltage regulation is minimum, then good. As example – two transformer having regulation 2% and 5% respectively, then the 2% regulation transformer is more efficient than 5%.
Transformer Noise :– Transformer noise is called “Hum” or “Humming Noise”. Humming noise induced due to vibration of laminated sheet by magnetic force.
- Minimum noise – at full load.
- Maximum noise – at no load.
Auto Transformer :- It has a single winding on iron core and a part of winding is common to both primary and secondary.
- Advantages :-
- Saving of copper
- Higher efficiency
- Better voltage regulation
- Smaller size
Ideal Transformer :-
- No winding resistance
- No leakage flux
- No iron loss
Losses of Transformer :-
- Core loss/Iron loss = Eddy current loss + Hysteresis loss
- Copper loss = Resistance of the winding
Latest Update: WB10 RESULT 2017 – WBBSE