Working Principle of Transformer
A Transformer is a static device which transfers electrical
power from one circuit to another circuit without change in frequency. During
this period frequency will be same in both circuits. But during this process
current and voltage will be different according to the type of transformer. Transformer
works on the principle of mutual induction or faraday’s law of electromagnetic
induction.
Faraday’s Law of Electromagnetic Induction
According to faraday’s law of electromagnetic induction:
“The rate of change in flux with respect to time is directly
proportional to the induced EMF in a coil or conductor”
According to this law if flux changing rate increases with
respect to time then induced EMF will also increases in conductor.
And if flux changing rate decreases with respect to time
then induced EMF will also decreases. In this principle the flux should be
variable.
Basic Theory of Transformer
Transformer is a static device which means it does not have any
rotation part, it’s all parts are static. A simple transformer has two
inductive coils which are electrically separated but magnetically linked to
each other by an iron core. This iron core provides a path of law reluctance which
causes mutual induction between two coils.
It has two inductive windings, first one is primary winding
and second one is secondary winding.
Primary Winding
We give alternate supply to primary winding using alternate
electric source.
Alternate flux is produced in this winding and this
alternate flux is linked with secondary winding by an iron core path. If
secondary winding circuit is closed, current will flow in this circuit
according to faraday’s law.
Secondary Winding
We take output supply from secondary winding. An EMF is induced
in secondary winding due to primary winding because primary winding is
magnetically linked with secondary winding. The output voltage depends on the
number of turns in secondary winding.
More about Transformer
Transformer rating is always taken in KVA (Kilo Volt Ampere)
not KW (Kilo Watt) because In Transformer rating does not include power factor.
If we also include power factor then we take rating in KW. It means
KW = KVA x Power Factor
Transformer depends on load power factor, so we take its
rating in KVA.
KVA = V x I
KW = V x I x Power Factor
Where V = Voltage and I = Current
If primary voltage is greater than secondary voltage then
transformer is called as step down transformer and if primary voltage is less
than secondary voltage then the transformer is step up transformer.