From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Sun, 15 Nov 2020 19:26:15 -0800
Subject: Re: [EE] Microwave Oven Transformers
Thread-Topic: [EE] Microwave Oven Transformers
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Another quick update.

To recap, this is a project to create a high current inductor to stabilize =
DC current up to about 100 Amps. I have an inexpensive lightweight lunchbox=
-size arc welder that works great with alkaline(6013) and low-hydrogen(7018=
) welding rods, but won't sustain an arc with cellulosic(6011) rods. My tho=
ught was to try adding inductance in series with the welding cables to hope=
fully allow use of cellulosic rods.

My first attempt used a stripped microwave oven transformer with 25 turns o=
f wire and a small air gap. Worked better with it than without it.

I then tried using the inductor from my other arc welder, a Miller Thunderb=
olt AC/DC. Using that inductor, the little lunchbox welder burned 6011 rods=
 "like butter", very smooth. The inductor from the Miller was very large, w=
ith a lot of turns of wire.

I tore my microwave oven inductor apart and rewound it with about 52 turns =
of wire, reusing my wire. Previously I'd used 4 strands of 12AWG wire in pa=
rallel, but this time I used the same wire with only 2 strands in parallel.=
 I also increased the air gap slightly.

It works great, I can burn 6011 rods like nobody's business!

Pictures to follow in a week or so, time permitting. Who knows about heat a=
nd duty cycle, will know more as this project progresses.

Cheers! Bob=20

________________________________________
From: Bob Blick=20
Sent: Wednesday, September 9, 2020 9:33 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Microwave Oven Transformers

Quick update. Here's the almost finished inductor made from a microwave ove=
n transformer. Right now with a gap of about 0.5 mm the inductance is about=
 1 millihenry. I will probably double to 1 mm which should lower the induct=
ance by about 30 or 40 percent. Although I could weld it together as it was=
 originally, I will just use the clamp as shown. The top plate is two piece=
s of wine barrel hoop butt welded together.

Final number of turns is 25. Wire is 4 pieces of #12 AWG copper wire wrappe=
d in more than 20 meters of 20mm wide polyimide tape.

Hand and cat to show scale.

Bob

--=20
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