Suppose 220v is applied to a transformer and getting 440 as output (means,turn ratio is 1:2). Now its core gets broken (cut a slice so that flux passes through air).

Now what will be the changes in input/output voltage, induced voltage, currents and losses?

Please somebody answer me...

 

You're beat buy a new xfmr there <10k$.

 

> You're beat buy a new xfmr there <10k$.

what kinda answer is this, I didn't get it

 

steveiee is saying if that actually happened to your transformer, buy a new one.

Adding an air gap to a transformer core will generally limit the maximum current, based on the difference in flux. The larger the gap, the greater the leakage, the smaller the maximum current.

The ratio of input vs output will also no longer be stable at higher load. The higher the load, the worse your ratio will be (i.e. 440 will slowly go down to 430, 420, 410 as load on the transformer increases.)

Forgive me for asking, but is this a homework question?

Mike

 

Bittu... do you mean insert an air-gap in the ironcore on which the 220V primary, and 440V secondary windings are wound?

Regards, Phil Corso

 

This sounds sort of like a homework problem to me. Just doesn't seem like a situation that I would expect to see in real life.

Given that, the magnetic coupling from primary to secondary would drop, causing a drop in secondary voltage. The exact amount would depend on the width of the gap and the cross-section of the core.

 

Thanks mike for responding in right direction.

Actually, I was asked this in my interview. I told almost like U said. But It seems interviewer was not satisfied. So, I asked it for discussion.

You are right that maximum current will decrease since saturation in core reached earlier now.

I told him secondary voltage will decrease, since flux gets decreased due to increase in reluctance of path.

But, Now I think, voltage won't decrease in sec. Because same decreased flux is for primary too. So, for a moment decrease in primary induced emf will be experienced which demands more current.this will lead more core loss. but secondary voltage will be according to turn ratio.

So, In my view, only core loss and primary current will increase(ignore saturation of core), but voltage will remain same(ignore voltage drop due to leakage flux).

More discussion will be appreciable.
Thanks.

 

@ Phil Corso,

Yes phil, U got me right.

Please explain it as u explained in many post. m waiting for ur valuable explanation.

<i>Moderators note: please refrain from using text speak when posting to the forum. It bothers a lot of forum readers and is difficult for non-native English speakers to understand. I regularly get email complaints about this all the time</i>

 

Bittu… let’s start by listing the key magnetic parameters of a two-winding iron-core transformer:
o Ac = cross sectional area of the iron core.
o Lm = magnetic-path (median) length.
o Rm = reluctance of the magnetic-material path.

If the magnetic-material property like permeability is known in addition to the above, then the B-H curve can be constructed, and the corresponding primary and secondary voltages determined.

Now, consider the introduction of an air-gap, of length, Lg, having a reluctance of Rg. Then, the total reluctance of the magnetic-path is the sum of the magnetic-material reluctance plus the air-gap reluctance, or Rm + Rg. And, because the reluctance of air is much greater than that of typical magnetic material, the total reluctance will essentially be that of the air-gap.

Thus, the following parameters will be affected:

o Effective length of the overall air-gap.

o Decreases permeability of some core materials.

o Changes the shape of the Flux Density vs Magnetic Field Strength (B-H) loop.

o Air-gap flux is further mmodified by parasitic flux development, such as fringing and leakage.

o Decreases excitation current losses.

o Smoothes out inrush-currents.

o Negatively impacts Voltage Regulation.

Bittu, I know the above discussion is difficult to visualize, so if you want a mathematical example, contact me off-forum.

Regards, Phil Corso (cepsicon[at]AOL[dot]com)