BEST Microwave Oven Transformer-MOT Rewinding Tutorial 

Thanks for making a video with clear instructions and voice without loud distracting stupid music !

I noticed that you were using a carpenters chisel ; I used a mechanics chisel and things didn't go as smooth. I had a time getting the winding out ! I ended up putting the transformer in a vise and just hammering away at the coils with a punch. After about two hours, I finally got it cleaned out. So, thats why I came back to watch your video ! Nice Job ! Like all of your videos ! Thanks !

Hi. Please let me know what thiknes could I on secondary for DIY power supply at 30v DC max 3 A. Thank you.

hi, is there any different if i accidently swap in ""LIVE"" voltage into ""NEUTRAL"" for primary with this kind of project? will it cause explosion???

Question. Theoretically speaking is it possible to wrap 6 gauge or whatever gauged wire ''loseley'' with slack or loops for adding taps? The sectional density would still be there in the core but all windings would be given a certain amount slack outside the core. Would it still work? I want to build a welder I got about 10 suitable MOTs but It's gotta be adjustable. I want to add a contractor switching wheel

Very good information given in the video. Many thanks!!!

Somewhere around 15 or 16 turns mine got all mixed up and not very uniform ... The last 2 or 3 were pretty tough getting them through ... I also used 10awg solid so it was extra tricky haha what a finger work out 😆.... I just now got finished rewinding it and have not tried it yet but I was wondering if you have any idea if it will work at all using a solid/single strand ..also I now dont have a working dmm ... 😣😞 haha ...

dear sir when i was removing secondary winding of mot i damaged the primary could you please tell me how many turns and layers requred on primary winding,?

I've been harvesting various parts of microwaves and I noticed that some of them don't have standalone transformers but have integrated components on a power converter. The converter feeds directly into the magnetron. Any recommended use for these other than desoldering the components for other uses? Also, is this typical of more modern microwaves?

Despite what others have said about the video I give a thumb up. You made everything very simple and to the point. For me it doesn't matter where and what material you're working with. What matters is what knowledge I get from it. Thank you for keeping everything down to earth!

very good video congratulations.i have one question, what if i use 220 volts on primary?

U r Excellent Teacher. I will rebuilt following your instructions. Thank you so much.

After watching this, I am impressed with your speedy system of MOT modification without separating the core. This made for a relatively quiet filament power source for my VTTC. Thanks for posting.

Excellent tutorial! Thank you a bunch!

Hi bro nice informative vedio , can i use the primary as the secondary for 220v and recoil the top winding for the primary and supply 110v through it.

what is the original mpedance of both sides? (estimated)

oke.. this is a really nice project!! went straight to the store and got me an old microwave which was returned for scrapping. they were happy to get rid of it and i was happy to have it :D must say.. i live in europe so my transformer is a 240V version, which i feel shows by thinner wires on the primairy side (compared to 120V) and more windings ending up in a higher resistence (2.5 instead of 0.5). took out the secundairy side and the red wires.. I did just so gently touch the primairy side with the hammer, only some slight deformation there..) resistance is still the same so i believe it will still be fine. it's really just minor. I feel i'll find out when i'll try it out. but i have a something else that bothers me more. At the end of the inner side of the wire there is something connected before it goes to the end pole (so between the beginning and it's pole). i don't know what it is. it WAS insulated (will do again but had to remove it before i could read it. it says ck01 and L145 and i have no idea what it could be. it is easily removed if i need to. fiddling withit i did notice some minor changes in resistence (max up to 9.0) anyone have any idea? would have loved to post pictures here but.. i'll try to add the links from dropbox below. www.dropbox.com/sh/c4xroh6boexpe79/AABtShZB3U6xHPRQ2oBotwFka?dl=0

Nice video.. One question though...if you used the grinder to sharpen the chisel, why not just use it to cut through the windings? or better yet, make a small incision at the weld on the side of the transformer, and separate the "E" portion from the bottom... So you to can slide the windings out whole, and easily rewrap the new wire. Then you can just re attach the bottom of the transformer to the "E" portion, and weld it back together, no problem....assuming you now have a welder.

It is CRITICAL that the two transformers are wound the same way to be connected in series. If one is wound "In Phase" (Same Direction as Primary)and the other is wound "Out of Phase". then the two in series will not work. If you wind one "Out of Phase, NOT in the same direction, 180 Deg off, Then you MUST wind the other transformer also "Out of Phase" to be able to connect them in series.If You have 1 MOT Primary wound opposite from the other, you can correct this by winding 1 MOT Out of Phase

Brilliant tutorial. Thanks so much.

thanks for the well explained answer!! although does the voltage on the primary have an effect on the output? As I have an dual 24v toroidal transformer , once that has been rectified and filtered I get almost 40V DC!! My house has a mains voltage of 251 AC maybe thats why?

Thanks for the video !.... has anyone used a rewound MOT, heat sink, capacitor & rectifier to build a 120 volt AC to 20 volt DC power supply for a DeWalt battery powered miter saw (or other power tool) ?

I would like to do this for a spot welder. Remove the shunts or not? Do I require thicker gauge wire? 4 gauge or larger? Will the 10 gauge not melt from the current?

Enjoy your shows though thanks

best transformer instructions. thankyou

Good video ,if I want to make a spot welder how long should be the secondary winding and how thick I don't have thick copper wire so can I take several thin wire and put together to make thick enough

Excellent Video!

It is very informative, thanks a lot. I congratulate you and thanks alot

Other info. I researched is that these mot have shunts; I didn't find any as I noticed you didn't either after watching your video. Thanks !

Outstanding video, thanks

Hello, I am rewiring a mot for 120v to around 28v with a output of around 10 Amps. I was wondering if 20awg magnet wire would be thick enough for the secondary coil.

İ watched many videos but i didnt learn information as much as your video even i dont have a good english😁Thank u

For winding the new wire, what length of 10 guage wire would be needed to make 16 - 17 turns for the welding circuit. ? OR approximately how long should the 12 gauge wire be to create the battery charger to reach 13 - 14 volts ?

Doing this I may have scratched the primary a tiny bit, you can see some of the copper, so how much will it affect it or is it no good? If it's no good can you rewind the primary coil?

Excellent video... Thank you for the AC to DC calc. While cleaning the transformer I took out all the paper and middle shunt. I remember I saw one you tube video. It say that piece should be removed for more room to turn the primary copper wire. So I hammer it out already. What does that piece of metal in the middle for? Used as spacer?

i cant finde this cable =( "age" its the same with cable sae 10???

Best video thanks bro

@electronicsNmore, thx for this great video. The only wire i have for winding is those which they use for the wiring of stoves & geysers. The outside + plastic is 4mm with 7 copper strands of 0.8mm each, i'm not sure how to measure the ga. Will this be OK?

Very good video you have a new subscriber!!

I have a mot from a 1000W Kenmore Elite. Rewound secondary to a rectified 14vdc. With small load 55w or no load the primary draws 7.5 amps continuous. Is this normal. I was going to try to make 10amp power supply.

Hi mate, can you tell the secondary thick wiring is clockwise or anti clockwise

Great job with patience

Be interesting to see what happens to Hz when a pot isadded with the cap bank? thanks again very interesting good presentation

Quick question... Do your primarys get hot when not under load / short circuit conditions? How long can the transformer remain connected before it gets hot? I have tried modifying 2 MOTs now and the primarys get so hot (No shorts between laminations and primarys). Is this just eddy current making the heat? Or is some kind of ballast required??

What a great video. How long of a piece of secondary wire did you use before you started to wind the secondary. I don't want to cut 10 feet and then find out that I am 5 feet short of finishing the secondary wind.

I followed your instructions and after I made a rectifier from 4 diodes I tested my output and was very happy to get 15.4 vdc . I soldered clamps on each lead and found an old battery which measured 4.4 vdc so I hooked it up. After 1 hour I checked it and it was at 10.2 vdc but what alarmed me was the transformer! It was too hot to touch! It buzzed VERY loudly...normal...but was so hot I couldn't possibly hold it without gloves on my hands. I immediately unplugged it to let it cool down. Any advice?

OK so I got a micro hydro turbine puts out between 60 and 80 volts only problem is it puts out like 30 amps, how can I tie it to a mot or anything to get more amps?

There is a lot of aluminum clad 10guage cheaper wire on Ebay, are there any complications with using this wire as opposed to the copper? I am trying to make a 12volt to 120 volt inverter. I am having difficulty finding any solid answers by doing a search. Thanks.

When calculating AC voltage to DC voltage what does the 0.4 number come from? is that the resistance of the secondary winding?

How many turns and what gauge wire for the battery charger ? Also does the gauge of wire play a factor in the number of turns ? Thanks !

I will rewind a Mot next days.I want to make a lead acid battery charger .I have a couple of 100A batterys.I have just one question : does it get hot during function? I was wondering if it s necesary to attach a pc cooler .Thanks

Would it not be safer to use the chisel from the side of the transformer - parallel to the primary - so there is much less risk of damaging the primary by going too far with the chisel?

I want to make it as a battery charger. How many rounds and which kind of wires I should use. Another question pls, How many amp I can obtain?

Good job. I saw you put an input capacitor to the transformer. Can you tell me how you have calculated the capacity? After you put the capacitor you have measured active and reactive power before the transformer?

Great vid, thanks.

What's the no load core losses of this thing?

It's easier to multiply the RMS AC voltage by 1.4142 to convert it to peak, which would be the DC voltage across the caps...but don't forget the voltage loss across the rectifier diodes, with a full bridge you are looking at around 1.4V TLDR: VDC=(1.4142 x VAC)-1.4 Assuming sufficiently large filter capacitors.

excellent

I live in flip-flops. I do everything while wearing them, from climbing mountains in Arizona, 20 mile bike trips, to construction work. I am very proficient with them, rarely get injured because of them, and because I never wear shoes, I have no toenail fungus! Well ventilated feet.

New to all of this just like making stuff lol . What other things have transformers in them? Can you use the Primary from another transformer as a secondary? What devices can I find a AC / DC rectifier ? Trying to build a welder I like trying not to buy anything any advice on where to get other parts

Nice video, the best hand held meter in the world for electronic repair is the one in your hand. The Wavetek 27XT, I've had mine for over 16 years and use it almost daily at my electronics job. Shame they don't make it anymore. Anyways nice video.

how to calculate with this. wire?

What has always confused me is the voltage is the number of turns but how do you know how much current you can draw? Say in the UK you have building site 110 volt output, how do they rate what you can draw in current? Thanks Ian

what if I wanted to get 3 wires from the primary (center tap) how would I wrap that?

anybody know what kind of glue they use on these mots, i am trying tear one apart but i need keep both windings clean and undamaged the transformer needs to be clean too. i have tryed heating the microwave in a small oven to get the glue to melt but didnt work out. i tryed soaking the whole thing in dish washing soap for days and it stll didnt work.

No mention about the shunts in the transformer core.........should they be removed or left inside......after you removed the HT coil and the Red wire..???

Is it really trash if the primary gets scratched? I saw a vid claiming to be able to fix the primary

how many volts should the two secondary wires put out. not the one that goes to 12 volts. can you please help on the inverter..

I used a hacksaw to cut mine off then drilled both sides out with a drill press. Easy as pie if you have a drill press!

I would like to use this application to solder jewelery together with solder wire , my question is how many turns would be needed to do this as I'm guessing that to solder I will not need the electrodes to be as hot as for welding.....can any onehelp or am I out to lunch on this one? Thanks much

I want to tell you that if you apply mains to the high voltage winding you can then get 50v ac out of the old 250v winding without doing any taking to pieces. You should know that taking out the shunt core reduces the inductance and the mains winding then takes a lot of current and the transformer will get very hot even with no load.

its a good idea , very nice

how much current would 4mm squared wire give out if i rewound a mot with it its household wire with 7 thick strands of single wire that make up the wire itself the mot has 6170w marked on it i believe its the rating of the transformer

Excellent tutorial! Out of curiosity does anyone know what the inductance of a primary winding on a typical MOT is? I am making a Choke-input filter to remove the ripple voltage from a 110V 4A dc power supply and looking to find or make a 3 Henry inductor. Is it viable to rewind a MOT with 18gauge wire to make an inductor of that size?

you can get more turns with magnet wire as the insulation is thinner.

OK this has been bugging me, so I'll ask. How come you chop down in the direction of the primary winding? Why can't you put the transformer on its side then chop to the middle, where there is nothing that you need to worry about damaging? Basically 90 degrees to what I see going on here. I am really interested in the rationale for why that would not work. Because it is just not coming to me.

Is the new primary you used, insulated magnet wire or just just ordinary insulated wire?

Went out and bought a copper grounding rod for 10$ at the home store. Is 8' of solid copper thats 1/2" around.. i sanded it down to just enough to completely fill the space in the transformer then dipped it in floor varnish 3 times along with the rest of the transformer. Cut off the bottom of the transformer though and sanded the varnish on the mating surfaces and a corner on each side. With the winding in its home i hooked one side to negative and othrr side to the positive electrode holder from my stick welder, rubbed a little tinning flux youd use for pipe brazing then with gloves and welding mask on and machine on 200a ac and just gotta make sure that you hit both sides at the same time so i used 2 pieces of wood to guide me and slapped together. No sparks came out and i switched off the machine as soon as i could get to it. Worked perfect.. two halves are together and wont come apart, the winding gives me 120v in and 2v out with enough current to blow my 1500a shunt so 2ka i guess.. dunno. But it makes a hell of a supply for an hho generator and can stay on with a fan indefinitely...

Hello sir I love your videos, my transformer gives me 24v ac but when I connect bridge rectifier then it drops to 19v dc I think that the bridge rectifier is eating up the voltage please guide me

How many feet of 12 or 10 gauge wire is needed if I wish to have exactly 12 volts DC later on after full wave rectification?

informative...

may i know how about the formula to rewind transformer turn to the voltage that wanted?

I've rewound a lot of MOT's. If you have access to a stick welder, I've found that its much easier to use a Dremel with a carbide cutting disc to cut along the weld that holds the laminations together. Usually, you can cut the weld on one side and wedge a flat screwdriver in the cut to pry apart the "top" of the transformer. After the "top" is off the windings will just slip out. When you're done rewinding, if you have a stick welder it's easy to put back together. Believe it or not, I've actually had success using a 150W soldering iron and solder it back together most won't have an iron that big though. When I have kept the laminations intact, a tool that makes short work of cutting the secondary is a oscillating saw, sometimes called a Fein tool. it makes a very clean, mess free cut and usually you can just push the leftovers out with your finger.

Very practical and smart guy...thank you

I just plugged mine in an it hummed really loud.. there's no nicks or scratches in the old primary.. Gonna watch some of your other videos to try an see what I am doing wrong. I'm shooting for 7volts for perchlorate electrolysis.

Is there a Problem with winding one for 240 to 30v ? Like saturation or something?

Please, could you give us the transformer formula for winding the secondary We use 220volts

Probably the easiest way to remove the sec. In the past I've used an angle grinder, slotted drivers, and a rubber mallet to remove both the primary and secondary....reusing the primary, winding a low voltage sec.....like you've done here. Twice I've had to 'roll my own' primaries. Not very efficient but neither is the stock transformer. You can do a lot of fun (inefficient) things with these.

I have little understanding of the science behind all this but I have a question and I hope you can educate me with an understandable answer. Would it be possible to take 2 of these transformers and combine the primary coils of both into one rather than winding your own secondary? I somewhat understand that the more windings result in more voltage? So by winding a new secondary with thick wire, I'm drastically dropping the voltage? So will using a primary from another transformer be too many windings, thereby resulting in too much voltage? I've seen plenty of these types of videos but I wish more would take the time to explain the science behind it all for those of us ignorant but wanting to learn.... I want to create a welder to repair my trailer and small other jobs. From reading reviews on Harbor Freights $100 welder, I'd be waisting my money. Also, would using more than 2 of these transformers wound like your way, show any benefit, such as 3 or 4?

Could I get 6.3v at 100a out of a 240v mot do you reckon? How thick would the wire need to be?

Hello, why must respect the meaning of the secondary winding in the direction of primary winding, thanks !

If you just want a rough transformer that will get you a certain voltage without being very efficient or powerful then this method is ok, but if you would like peak performance and power like in a mot stick welder or high amperage battery charger you should cut the transformer to (CAREFULLY) pull the whole coils out of the core, knock out the magnetic shunts, add a few (about 10-20) more turns to the primary side, and make a simple winding spindle with blocks of wood slightly oversized to the transformer core to tightly (key word TIGHTLY) wind some SOLID core wire of preferably the enameled variety (I've made similar wire by wrapping teflon pipe tape around bare copper wire) and letting some thin enamel of some kind (clear fingernail varnish works great) soak in between the windings or brushed on between layers to keep the copper winding solid so it doesn't fall apart on you. A lot of people consider this overkill but there's very little extra work for a HUGE increase in performance. You're not just increasing the power handling with the extra copper, but the tighter windings, extra copper, greater fill efficiency, removing the magnetic shunts and more primary windings give a much higher performance to effort ratio and some MOT's can be ran continuously at a couple kilowatts or more with this arrangement. To be honest, if I just needed something lower powered like what this guy is doing I would just add one of those cheap buck boost modules to a laptop power brick, infinitely variable voltage within a certain range, automatically smoothed output, both voltage AND current control, higher efficiency on your power bill, and can fit in a smaller space, and the price is usually pretty similar to what you'd have to pay for all of the components to make the mot power supply work since you need extra diodes and wire and capacitors yet you lack several of the features of the buck-boost-brick setup. If you need higher voltage then you can put a couple buck-boost-brick setups together in series as long as they are otherwise isolated.

What are thoseee!! 👍👍 Good video

Thanks for taking the time to do this video. I gave this a try myself today and it was a little tough (knocking the coil through the core took a fair bit of effort and experimenting with different tools) but with a bit of elbow grease and one severely blunted wood chisel later I managed it. One thing I'm not sure about is that you mention putting the windings one on top of the other, but what are you doing when you reach the top? Do you then progressively wind lower and lower?

hi i have one question.when i turned battery on charcing my TRANSFORMER is overheating

my lg microwave wen I start is working BT is smoking from transformer n my c/breaker goes trip

Great video. where did you get D.M.M to buy, thanks.

New subscriber here.

Insert a short piece of 1/16" piano wire (about 4" each) being at the top and at each end on one side of the primary (tap in lightly with hammer). Cut close to the iron core with a fine tooth hacksaw. The piano wire is too hard for the hacksaw blade to cut so it stops the blade preventing the primary from damaged. I just cut the secondaries off two transformers. Ten minutes each and no damage to primaries.

ok thanks i try