• Transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of electromagnetic  induction between two windings.
      Principle of Transformer:
  • It depends upon Faraday's law of electromagnetic induction.
  • According to Faraday's laws, rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil".
      E= N dÏ• /dt

Where,

                E = Induced EMF

                          N = the number of turns

                   dÏ• = Change in flux

                   dt = Change in time
  • The energy transfer usually takes place with a change of voltage and current.
  • Transformers either increases or decreases AC voltage. 
     Working of a transformer:
  • Transformers consist of types of conducting coils as primary winding and secondary windings.
  • The input coil is called the primary winding and the output coil is called the secondary winding of the transformer.
  • There is no electrical connection between the two coils instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer.
  • The two lines in the middle of the circuit symbol represent the core. Transformers waste very little power so the power out is almost equal to the power in.
  • The primary coil and the secondary coil posses high mutual inductances. If one of the coils is connected to the source of alternating voltage, then an alternating flux will set up in the  core.
  • This flux gets linked up with the other coil and an electromagnetic force is induced, as per Faraday’s law of electromagnetic inductance.
  • Depends upon the voltage ratios from primary to secondary windings, the transformers are classified as step-up and step-down transformers.
     - Step-up transformers:
  • The secondary voltage is stepped up with a ratio compared to primary voltage. This can be achieved by increasing the number of windings in the secondary than the primary windings
  • In power plant, this transformer is used as connecting transformer of the generator to the grid.
     Step-up Transformer
     - Step-down transformer:
  • It used to step down the voltage level from lower to higher level at secondary side.
  • The winding turns more on the primary side than the secondary side.
  • In distribution networks, the step-down transformer is commonly used to convert the high grid voltage to low voltage that can be used for home appliances.
Step-Down Transformer
     Applications of a transformer:
  • Regulating alternating current
  • Stopping and starting the flow of electricity
  • Battery charging