Transformer transforms voltage from one level to other level without changing the power and frequency. Transformer is a static electrical equipment and it does not have any moving part. The transformer has a magnetic CRGO steel core and two copper winding, one act as a primary and other act as a secondary.
The transformer losses are very less because there is no moving part in the transformer, thus transformer is a high efficiency equipment. The transformer functions on the principle of Faraday’s law of electromagnetic induction.
When AC voltage is applied to primary of a transformer, the counter EMF is generated in the primary according to rate of change of current. The counter EMF generated in the primary limits the current in the primary.
The counter EMF is zero if the DC is applied to the primary and the transformer can’t be operated with DC. The flux is generated in the primary when alternating voltage is fed. The flux travels through the magnetic core and the alternating flux gets linked to the secondary. The alternating flux induce AC voltage in the secondary.
The RMS value of the voltage induced in the winding depends on the frequency, number of turns and the flux. Ep = 4.44Np fФm
Es = 4.44Ns fФm
Ep = Induced EMF in primary winding
ES = Induced EMF in secondary winding
Np = Number of turns in primary winding
Ns = Number of turns in the secondary winding
f = Frequency
Фm = Flux in the core
There are two type of transformer single phase transformer and three phase transformer. The working principle of the transformer is the same. The single phase or three phase transformer can be used a step down or step up transformer.
The single phase transformer has core and winding as its main part. The winding has resistance and to keep the transformer copper loss down the winding material of small resistance value is selected.
The laminated core is used to keep the eddy current losses to minimum value. The thin lamination of thickness 0.25 to 0.5 mm is used and the laminated sheets are isolated from each other. The insulating varnish is used for this purpose.
The transformer 500 kVA and above are of generally oil filled type. The transformer oil is used in the transformer tank for the insulation and cooling purpose.
Application of Single phase Transformer
Single phase transformer is widely used in low voltage application. The single phase transformers are mostly used to step down the single phase supply 220 volts to lower voltage. The transformer is used for power supply to electronic equipment. The transformer is used in the AC/DC rectifier, electronic circuits etc.
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