Transformer

Introduction :

The device which is used to stepping up or stepping down of voltages is known as transformer.They can step up and step down A.C voltages only.When the energy is transformed into a higher voltages the transformer is called step up transformer and otherwise is called step down.Most power transformers operate at constant voltages which means that if power varies the current varies while voltages remains fairly constant.

Single phase transformer :

A transformer is a static electric machine which transfers electric energy from one circuit to another circuit without any changes in the frequency.Due to electromagnetic induction principle the transfer of energy take place.

It consists of three essential parts 

1.primary winding

2.secondary winding

3.Laminated iron core

The alternating current in the primary winding sets up an alternating flux in the core.The A.C supply is  given to the winding is called primary winding.The secondary winding feeds the load.The secondary winding is linked by most of the flux and emf are induced in the two winding's.The emf induced in the secondary winding drives a current through the load connected to the winding.Energy is transferred from one circuit to another through the medium of the magnetic field. 

Rating of transformer :

• The rated quantities of transformer  its power,voltage,frequency,etc are given in manufactures name plate,which should always be arranged so as to be accessible 
• The rated duty of a transformer is determined by the quantities given in the name plate.
• The rated power of transformer is power at the secondary terminals,indicated in the name plate,and expressed in KVA.
• The rated primary voltages is the voltage indicated in the transformer name plate.If the primary is provided with taps.
• The rated currents of the transformer,here primary and secondary currents are indicated in the name plate of the transformer.

Parallel operation of a  single phase transformer:

The necessity of parallel operations of transformer is felt when the amount of power to be transformed is greater than that which can be handled by one transformer.

• The voltage ratings of both primary and secondary must be identical.
• The transformer must be properly connected with regard to polarity.
• The equivalent impedance should be inversely proportionally to the respective KVA ratings.
• The ratio of equivalent impedance to equivalent reactance  of all the transformer should be same.

click here to transformer basic definitions :