what is the purpose of air gap in transformer???

 

reducing the magnetic flux between the two coils that are magnetically attached. primary and secondary. This is used to indirectly set the voltage inducted to the secondary coil.

 

reducing the magnetic flux between the two coils that are magnetically attached. primary and secondary. This is used to indirectly set the voltage inducted to the secondary coil.

Please don't guess if you don't know the answer, others may believe you.

The air gap is used if the transformer winding also carries a significant DC current as well as an AC one.
This is because otherwise the core would become magnetised in one direction by the DC and be less effective for the AC coupling to the secondary.
The (very small) air gap is essentially non existant to the alternating flux generated by the primary, but blocks the flux generated by the DC.

 

so you mean air gap is used for ac saturation, then tell me if my input supply to the transformer is ac then how dc current is generated in the transformer?

 

so you mean air gap is used for ac saturation, ...

studiot stated: (emphasis mine)

The (very small) air gap is essentially non existant to the alternating flux generated by the primary, but blocks the flux generated by the DC.

 

The air gap does not "block" any magnetic flux (AC or DC) - it simply increases the total magnetic circuit reluctance.

 

DC is not 'generated' in the transformer.

Transformers of themselves don't generate anything. It is all down to what is impressed on the transformer by external means.

Some applications impress both AC and DC on the primary at the same time for circuit continuity reasons, for example an output transformer in an audio amplifier also carries DC biasing voltages.

This DC would shift the magnetic operating point in an undesirable manner without the air gap.

TNK I agree 'blocks' was poor terminology. Sorry

 

what is the purpose of air gap in transformer???

What kind of transformer are you referring to?

A grid frequency (50/60 Hz) transformer? If so, what is the application?

Or, perhaps, an audio frequency transformer?

Or a high frequency switcher transformer, such as a flyback transformer?

Why do you think there is a gap in the transformer (core)?

Without more information it's difficult to answer your question.

 

I was given an assignment to study construction,working,function and operation of transformer. So i just got stuck in AIR GAP

 

So i just got stuck in AIR GAP

That doesn't answer our questions.

The Electrician was correct to point out that many if not most transformers do not have an air gap.

There are also devices called chokes that look a bit like transformers. These are wound on C cores and do posess a gap.

Where did you get the notion of an air gap?

 

while studying my text book, the sentence was " air gap is essential in transformer"

 

while studying my text book, the sentence was " air gap is essential in transformer"

What kind of transformer? If it's an ordinary transformer intended for service on a grid frequency (50/60 Hz) source, then very few such transformers have an air gap; it's certainly not "essential" for the vast majority of such transformers.

There are some that do have a gap, such as a current limited transformer for powering neon tubes, but most 50/60 Hz transformers do not have a gap.

Can you re-read your text and verify what kind of transformer they are talking about. You might even take a picture of that page in your text, and post it as an attachment.

 

the topic is PRINCIPLE OF ACTION OF TRANSFORMER

 

the topic is PRINCIPLE OF ACTION OF TRANSFORMER

We already knew that you are asking about how transformers work in general. But to help you, we need some more particular information.

That is why I asked you to do this:

"Can you re-read your text and verify what kind of transformer they are talking about. You might even take a picture of that page in your text, and post it as an attachment."

Your reply hasn't done this, so I can't help you any further until you do.

 

Don't the air gaps lessen the Eddy currents

 

If you look at this thread they are discussing just such a C cored inductor. Note the air gap at the bottom.

http://forum.allaboutcircuits.com/showthread.php?t=32544