Single Phase Transformer and Application of Single Phase Transformer

Last Updated on February 2, 2024 by Electricalvolt

The transformer transforms voltage from one level to another without changing the power and frequency. The transformer is static electrical equipment, and it does not have any moving parts. The transformer has a magnetic CRGO steel core and two copper winding; one acts as a primary, and the other acts as a secondary.

What is a Single Phase Transformer?

As its name implies, a single-phase transformer functions on single-phase AC power. It has two parts – magnetic and electric part. The CRGO magnetic core is a magnetic part, and the primary and secondary windings are the electric parts of the transformer.

Transformers, whether single-phase or three-phase, function with AC because DC can not produce the electromagnetic field. They are highly efficient because they do not have moving parts.

When the primary of the transformer receives AC, it generates magnetic flux. The magnetic flux travels through the core links with the secondary winding through mutual induction. The linked flux induces a voltage in the secondary of the same frequency as the AC current in the primary winding.

When AC current flows through the primary winding of a transformer, it generates a magnetic field. This magnetic field travels through the transformer core and links with the secondary winding through mutual induction. As a result of this linked magnetic field, a voltage is induced in the secondary winding that has the same frequency as the AC current in the primary winding.

Working of Single Phase Transformer

The transformer losses are very low because there is no moving part in the transformer, and thus, the 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 the primary of a transformer, the counter EMF is generated in the primary according to the 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 an alternating voltage is fed. The flux travels through the magnetic core, and the alternating flux gets linked to the secondary. The alternating flux induces an 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 the primary winding
ES     = Induced EMF in the secondary winding
Np     = Number of turns in the primary winding
Ns     =  Number of turns in the secondary winding
f        =  Frequency
Фm   =  Flux in the core


The single-phase transformer has a core and winding as its central part. It has two winding- primary and secondary winding. The winding has resistance, and to keep the transformer copper loss down, the winding material of a small resistance value is selected. The winding is placed around the laminated magnetic core made of silicon steel. The magnetic core provides a low reluctance path to magnetic flux. The steel core minimizes the hysteresis loss.

construction of single phase transformer

The laminated core keeps the eddy current losses to minimum value. Thin lamination with a thickness of 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 transformers with 500 kVA and above ratings are generally oil-filled type. The transformer oil is used in the transformer tank for insulation and cooling.

There are two kinds of single-phase transformer constructions.

The single phase or three-phase transformer can be used as a step-down or step-up transformer.

Application of Single Phase Transformer

  • Step Down of Voltage: The single phase transformer is widely used in low-voltage applications. The single phase transformers are mainly used to step down the single phase supply 220 volts to lower voltage. The transformer is used to supply power to electronic equipment. The transformer is used in the AC/DC rectifier, electronic circuits, etc.
single phase transformer
  • Regulation of voltage in electronics equipment
  • Applications in lighting and heating devices
  • For increasing voltage where incoming power supply has low voltage.
  • Increasing voltage in home inverters
  • Residential and commercial lighting system
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About Dr. S S P M Sharma

Dr. S S P M Sharma B is Associate Professor in School of Mechatronics Engineering, Symbiosis University. He has more than 8 years of experience.

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