Here's a microwave oven transformer that's been modified into a dangerous little device. Now it can pump out 800 amps of electrical current, so let's use it to melt some metal!
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Bowtie412 months ago

Would more turns on the secondary give more current?What about more turns in the primary?Can the core be solid steel instead of laminated?Lotsa questions,but I'm looking for more amps,and since I have a mill,thinking of scaling up the MOT to 2x size with a custom core if possible or feasible.

The way I understand transformers, it's all about the ratio of the windings (primary to secondary). So if you maintain the amount of windings on the primary and increase the windings on the secondary, then yes, the current increases. In terms of the core, solid steel becomes permanently magnetized if exposed to a powerful enough magnetic field.

ehasler4 months ago
It is a good demonstration piece for showing low voltage with high current
Mich6310 months ago

Would this work as a smelter for iron? I have a bunch of rebar lying around, and I'm thinking of trying to melt it down into blocks, then forge them into swords.

dillonxti1 year ago

have any experience with flybacks

herpingdo1 year ago
@Wildfire: If you mean using a car battery as a power source, then I would say no. The voltage you would be getting out of the secondary would be way too low to penetrate anything.
Hello Wildfire Phoenix here. This looks really cool and is something that I will do with microwave transformers (definitely an array of them).

I was wondering could someone, swap the plug for a light switch attached to a powerful car battery for this amazing metal melter?
Well done, sir -- you've earned another fan! The true gem for me though, at the end of the video: high temp solder! *smacks forehead* Thank you for solving the mystery of those PCBs in my parts bin, that my soldering iron won't touch! lol! Do you suppose that components de-soldered with your MMMOT are still any good?
Could this be adapted to make a metal melting furnace?
A high speed furnace would be so awesome! And handy!
herpingdo1 year ago
It works quite well, and I've not managed to break it yet, and I am only using 4ish gauge wire.
herpingdo1 year ago
I browse Instructables quite a bit, but I've never bothered to make an account. I made one though, just to comment here.

I saw this project, and remembered I had a MOT somewhere. I found it the other day, and I decided to modify it. The only tools I had to work with were a 10 year old hacksaw with a dulled blade, and a hammer. 6 hours of intermittent hacksawing and bashing later, and the weld was finally broken! I tapped the primary out with ease, but the secondary was a different story. I sawed and bashed and did everything I could with my tools to it. No luck whatsoever with getting that out. All I managed to do was wedge it in a bit better. I decided to make a trip to the hardware store, and pick up some cable and some tools. I got a chisel, a new blade, and a rubber mallet. That still wasn't enough to bash out the secondary though. I even tried drilling it out a bit, but that was useless. So I decided to bake it at 250 for about an hour, When it came out, I slowly chiseled and hammered and pried away at the secondary, until finally it was all gone. I now wish I had taken a picture of the huge pile of copper strands all over my workbench. From there, it was an extremely easy build. I cable-tied the transformer back together once I was done, and I was ready. At that point it was about midnight, so I figured I would have to wait until the morning. Morning's soon, so I'll let you know if it works or not once I test it! Wow, I've just written a bit of a novel here.

tl;dr: It is extremely difficult to build one of these without the proper tools. Buy the right tools, and bake the MOT in an oven for a bit if the secondary is stuck.
Norway19731 year ago
Could you add a clamp on one cord like the one welding machines and some sort of tip on the other cord so this could work like a plasma cutter? :-)
Can you wire it in parallel or series of a MOT with its original secondary to get 800 amps@ 2000 volts?
Is it just mine, or does you transformer also make a vibrating humming noise? I used two gauge wire as you did, and mine makes a loud humming/vibrating noise. Is that suppose to happen?
Yes. That's the hum of 60Hz AC
Ok. Thanks, just wanted to make sure. Mine doesnt seem to work as fast as yours. The voltage rating is 1.5 volt output, and i dont want to screw up a volt meter measuring amps...
Could your transformer, connected to coils, heat high enough for an aluminum melting furnace?
Are you talking about an induction furnace? I think that requires a very high frequency, so this set-up wouldn't work for that.
I am not easy to impress.....but you have. great videos.....I am going to work at improving my own to measure up.

As an electrician, 30 plus years, I would be interested what the modifications are to the microwave to have the 3 volt out put and high amperage.

Care to share?

Aquaponic Glenn at
I'm not sure if I ever saw your comment before, or answered you? I put up a new video awhile ago on how to make the metal melter. Let me know if you need a link? Basically just replace the secondary with 1-2 turns of 2 AWG copper cable. All the best!
mr fat2 years ago
This and your spot welder got me in and your You Tube work has made me a huge fun and subscriber! But with your slime and home made solid fuel rockets my five year old daughter is keeping me busy! Keep up the awesome work! Thank you from Alden and my daughter Reghan
The King of Random (author)  mr fat2 years ago
Hey Alden! Thanks for your comment and the feedback. It's nice to hear, and tell Reghan I'm glad to have her as a fan :)
SkeptiCol2 years ago
Must.... make......NOW!
The King of Random (author)  SkeptiCol2 years ago
Haha .. yes, do it!
karl_rotsen2 years ago
hi can you use that thing to make an induction heater/smelter?
The King of Random (author)  karl_rotsen2 years ago
Probably? I'm not sure yet, but it's on my list, and when I learn how, I'll make a new video on it. Thanks for asking!
meritsetgo2 years ago
you just saved me hours of backbreaking work trying to cut rivets from angled iron by sawing them thru with my sawzall, instead, i just melted them!!!
The King of Random (author)  meritsetgo2 years ago
Seriously!? That's creative! Thanks for letting me know :D
poofrabbit2 years ago
Hey congratulations on being a finalist in the hack it contest! Good luck to you!
The King of Random (author)  poofrabbit2 years ago
Thank you! I didn't know that I was!!
samaddon2 years ago
Hey, grant are you unknown of the competitions on instructable all you need to enter and i have the confidence that you will be i am waiting to vote for you!
The King of Random (author)  samaddon2 years ago
Thanks my friend :)
samaddon2 years ago
Hi! there,
that's hot but may i know what's the guage and turns of the primary coils of the transformer and what's the approximate cost of that???? cause i need to build it!
Samad Haque.
The King of Random (author)  samaddon2 years ago
Thanks Samad.

I'm currently working on a video on how to build this. It cost me about $4 for the wire and lugs because I got some scraps from my brother. The MOT was free out of a microwave.

The video should be done in a couple of weeks. I used 2 AWG insulated stranded copper wire.

st00pit2 years ago
Awesome video, nice to see one that shows how easy it is to experiment with a MoT.... very dangerous though of course! made myself a 4MoT arc welder and a single that runs a Jacobs ladder in my "laboratory" haha (the garage!)...
The King of Random (author)  st00pit2 years ago
Very nice!

I made a 1 MOT stick welder, but you can imagine it was barely enough power to burn a 1/16th rod.

Why did you use 4 MOT's? I've heard 2 is common .. but 4? :) Please tell!!

Thanks for your compliments!
ringai2 years ago
Have you considered making a small induction furnace to melt metal in a crucible?
The King of Random (author)  ringai2 years ago
I have considered it! I haven't much knowledge yet on how to do it. Have you?
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