Hi I'm currently rewiring a transformer. I ground the top wields off and took it apart. The 120V. winding are fine and I'm stepping it down to 12V. I was surprised to find a second set of laminated iron in-between the 120V and the other two sets of windings. What is this for and should I put it back in between the 120V and the 12V when I install my new windings?

 

A picture would help ! Maybe someone already knows what you mean, but I don't.

 

I can't figure out how to post a pic. Its asking for a "url" format? and won't accept my picture. Can I put it in an e-mail and then send it to this web site?

 

Try explaining it. Someone may get it.

What would the core look like with no windings?

E and I?
O?

What was original purpose?
Microwave?

 

Maybe you are talking about the magnetic shunt? If so it should be driven out if it is and is possible.
Max.

 

Picture....................................

Per email................

"The two things sitting on top that look like candy bars are actually laminated iron rapped in paper. They fit in-between the windings of which only the 120V is installed."

 

Looks like a mwo transformer.

Remove, like MaxHR says unless you need to limit current.

 

So then I take it that reinstalling these little bars in-between the two windings is not going to do me any favors. I am still wondering what the heck they are for. I can't see how they would act as current limiters but then it's obvious that I'm still learning about the behavior of transformers.

 

So then I take it that reinstalling these little bars in-between the two windings is not going to do me any favors. I am still wondering what the heck they are for. I can't see how they would act as current limiters but then it's obvious that I'm still learning about the behavior of transformers.

Maybe this will help you -
http://www.magnet.fsu.edu/education/tutorials/java/magneticshunt/

 

MaxHR will explain.
Magnetism theory is my weakness.

http://info.ee.surrey.ac.uk/Workshop/advice/coils/leak/weld/index.html

From that site.

"The flux generated by the primary winding need no longer travel through the secondary in order to form a closed loop. It instead has the option of following the shorter path through the bar; and this is what most of it will decide to do"

If only I could understand.

 

The MOT has current limiting.
The Magnetic shunts will limit the secondary current.

So If u need to use lower secondary voltage like me, just don't use the magnetic shunts.

Googling will help you. Try googling MOT rewinding

 

Thank you Headroom and Short buss. Now I understand. I really appreciate you guys.

 

Another example where it is used is in SMAW (stick) welding, the O.C. voltage of the transformer could be around 100vac, so when the arc is struck, (short circuit) the current would exceed the rating of the transformer and you would not be able to regulate the welding current.
By introducing a magnetic shunt the voltage collapses to a suitable selected degree depending on the thickness being welded by adjusting the shunt.
This shows a bit about shunts and other methods used, particularly fig 2 & 5.
Max.

 

That's very cool! As one of my next projects is going to be a wielder that's a wonderful thing to learn and apply.
Thanks again ,, Mr. Headroom

 

Hay Mr. Headroom Figures 2 and 5 in what? I could find no attachments or references.

 

..Oops! http://electriciantheory.blogspot.ca/2013/04/welding-transformers_17.html
Max.

 

Max ole buddy ole pal.
Again thank you very much! That web page is really nice/basic/and very helpful.

 

The link in #10 was specific to welders.