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Thursday, 4 April 2013

What is transformer ? Construction of transformer

Transformer and its construction:-
Transformer is an electrical device, which transform voltage in high or low voltage.In simple words it convert voltage of any amplitude to high or low. Thats why it is commonly known as electrical transformer.
In transformer there are two winding one is known as primary and other is known as secondary winding.Both windings are separated and have no direct connection between them.These winding are of insulated copper wire wounded on a iron core.This copper wire should be insulated other wise they short together and produce huge spark.
Transformers are rated in watts or some times KVA.In both sides of transformer power remains the same only difference lies in voltage and current.
Transformer works on the principle of faradays law of electromagnetism.When current passed through the primary side of transformer it produce magnetic field, this magnetic field induces in secondary winding of transformer and produces current in opposite to that of flow

ing in primary side.
Types of transformer:-
     There are two types of transformer step up and other is step down.
Step up transformer is used to increase voltage, what ever voltage we inputs in a transformer it gives out high output voltage of same frequency as input frequency.As stated previous power remain same as power is the product of current and voltage so in step up trasnformer we are increasing voltage, this means we should have to decrease current in order to make power same in both sides.
This type of transformer is commonly used in UPS uninterrupted power supply.
So main function of step up transformer is to make voltage high and current low. In this transformer number of windings on primary side is less than the number of windings in secondary side.
Now coming towards the step down transformer, step down transformer is used to decrease input voltage at output while keeping the frequency constant means this transformer is commoly used in radios, laptop chargers, power supply and many other place where we need less voltage then coming from power supply company which is almost 220V AC, if we want to convert it 12V AC then we have to choose step down transformer of about 12V.
If you connect secondary side of transformer at input voltage of about 220V Ac and primary side at output, it will explode with a huge spark this is because you have connect low voltage side to high voltage and winding in low voltage side cannot take such a high voltage and starts to melt its internal insulation, after removing insulation bunch of secondary wires make contact with each other and cause spark, so be careful while connecting the transformer, its primary side is always connected at input and secondary side at output.
Testing transformer:-
If you have a transformer and you don't know which side is primary and which side is secondary, some time there is no label of primary and secondary side.
Take a digital multimeter and move knob to its 10 ohms resistance and connect its probe to primary side of transformer, note we are know talking about testing of step down transformer whose primary side has more winding than secondary, read the reading if it shows 0 ohms then it primary side other wise it will be secondary side.In step up transformer, secondary side should have 0 ohm resistance.
       Here is farmula for calculating primary and secondary winding.

                     Ns/Np = Vs/Vp

           Ns  : Number of  Secondary side winding
           Np  : Number of Primary side winding
           Vp  : Voltage at primary
           Vs  : Voltage at secondary