Definition
A transformer is a device that transfers electrical energy from one
circuit to another through inductively coupled conductors—the transformer's
coils.
A varying current in the first or primary winding creates a varying
magnetic flux in the transformer's core, and thus a varying magnetic field
through the secondary winding.
This varying magnetic field inducesa varying electromotive force
(EMF)or voltage in the secondary winding. This effect is called mutual
induction.
The phenomenon of electromagnetic induction was discovered
independently by Michael Faradayand Joseph Henryin 1831. However,
Faraday was the first to publish the results of his experiments and thus
receive credit for the discovery.
Faraday's experiments including winding a pair
of coils around an iron ring, thus creating the first toroidal closed-core
transformer.
The first type of
transformer to see wide use was the induction coil, invented by Rev. Nicholas
Callan of Maynooth College ,
Ireland
The Ideal Transformer
A lossless device with an input winding and an
output winding.
The transformer has Np turns of wire on its
primary side and Ns turns of wire on its secondary sides. The relationship
between the primary and secondary voltage is as follows:
The relationship between primary and secondary
current is: Np ip (t) = Ns is (t)
Note that since both type of relations gives a constant ratio, hence the
transformer only changes value of the magnitude of current and voltage. Phase
angles are not affected.
