REWIRING A MOT (Microwave Oven Transformer)

If you are able to save the secondary you can make a great de-magnetizer out of it.
I use about 24 volts AC on it but it will probably take much more.
Just slip the magnetized object through the center.

Nice idea! To do that one has to dismantle the laminated core of the transformer. In my case, as you can see below, I must use a grinder to cut the weldings, remove the bottom part and then I have to reweld it. I'm not sure that such a surgery it will not affect the behaviour of the core!
If you have no intention in reusing the core it's easy to do it.

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UPDATE
After months of use (delivering some 40 Amps) the transformer works as designed without any problems of overheating!
 
Good read over a cuppa java. Enjoy the resourcefulness.
/me wishes that I fully understood electricity.
 
Good read over a cuppa java. Enjoy the resourcefulness.
/me wishes that I fully understood electricity.

He he he Electronics is easy if you relate it to some things you know!
For us the mechanically minded is easy to relate to ...water

Mimms.jpg

This comes from an excellent book I have bought some 30 years ago!

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Petros
 
Good read over a cuppa java. Enjoy the resourcefulness.
/me wishes that I fully understood electricity.

He he he Electronics is easy if you relate it to some things you know!
For us the mechanically minded is easy to relate to ...water

View attachment 253329

This comes from an excellent book I have bought some 30 years ago!

View attachment 253330
Petros
Coincidentally enough, I just bought that book at a used book shop. I bought all Forrest Mims' mini notebooks back in the 90's but did not buy this one. I am happy to have most of his books now.

Sent from my SM-G950U using Tapatalk
 
Guess I now know what I am going to keep my eyes peeled for!
 
Around here old microwaves for free for the asking. I posted on facebook that I was looking for one and had 3 offers in a matter of hours.
 
Around here old microwaves for free for the asking. I posted on facebook that I was looking for one and had 3 offers in a matter of hours.
Enjoy it while it lasts. I've been a microwave hound for years, wishing death on my friends' & family's microwaves so that I can harvest the precious transformer bounty within. But lately I've been getting "inverter" microwaves which have no 60hz transformer, and value to me.

Maybe I need to adapt and start building high power switching power supplies from the new inverter microwaves. Adapt or die!
 
Really behind the "eight ball" on this one. But it's still active, so I might add some comments~~~

First off, the flat copper sheet stock is a very elegant solution. I love it. Having built several "home made" transformers for my models, the wiring was small enough that everything fit so I never pursued things any further in that direction. I may build a couple just to play with the idea. I am "old school" in regards to transformers. I use "fische paper" anywhere something touches the core, the "figure 8" iron in the middle.

Comments now; first off: the insulation paper referred to is called "parchment" paper. Wife has several rolls in the kitchen which may well soon become (several -- 1). When warm weather comes back, it's too cold right now. Since the copper foil is so thin, there may well be a couple or three layers per turn. With the parchment paper between turns.

When I make the wraps on the core, I use a wooden "guide" on each end. A piece of dowel rod split down the middle and glued half on each side. This avoids sharp corners on the first layer of "whatever" copper is used, the most likely place for insulation to fail. I usually make what I need on the wood lathe but the basic idea is to split a piece of dowel.

The other comment is to try a copper foil from a surplus house. I use Marlin P Jones, there are many others. The foil is available in several widths, specifically one inch and half inch. Well, just under that at 25mm and 12mm. My biggest concern is low voltage at a moderately low current, just a few amps. But I need several sources that are electrically isolated. To isolate them magneticaly is acceptable, so long as there is no electrical connection.

Using the foil strips would allow several secondary windings to be wound on a single core. Using the narrow, 12mm, strips would allow me to "stack" more windings on a single core. The end result being one transformer with multiple windings. Instead of multiple transformers having one with multiple windings. Wiring is easy to dress, the cores not so much.

The theory, in my mind anyway, is to take two strips and stick back to back. The parchment paper for insulation on each turn. The 12mm(1/2") strip would make two coils, one on top of the other. Then two more above. All on one core~~~

That's my quarter's worth, here's hoping someone can use the information.

Bill Hudson​

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