Make a 240V MOT High Voltage Power Supply With 120V Transformers





Introduction: Make a 240V MOT High Voltage Power Supply With 120V Transformers

I love to play with MOT's but the only breaker i have to power them off of it only rated for 15 amps, so i decided to see if I could power them off a 240V outlet my dad made for his welders and air compressor and sure enough, it works! So here i will show you how to make a great MOT power supply very easily and for a very low price!

*A MOT can kill you instantly or give you a really nasty shock and they are not toys, I have been shocked by one and it was freaking scary and painful so BE CAREFUL! i am not responsible to any damage caused!

Step 1: You Will Need

Two MOT's
A light switch
A inlet from a computer power supply or something like it
A PFC capacitor (optional). 20uF at 250V+ should work just fine
Some .250" female spade connectors (bag of 50 for $2.20). You will also need some smaller ones for the inlet but I don't know what size
Some 14 awg wire. Speaker wire or an old power cord will work just fine
A 12" piece of 2 x 4 
A soldering iron and solder
A drill
Some screws. I used #8 x 1/2" screws from Home Depot 

Step 2: Position the Transformers

The first, and main thing to position are the transformers, everything else will be built around them. I prefer to put them on the right hand side of the board and have the all the other stuff in the left side. I put them primaries connections facing the back and the secondary connections facing the front. As you can see, the two transformers I am using are very similar except on has a small lip sticking out the side so I put this one on the left so the other transformer will over lap it and cover it up. Because one side of the transformer was on top of this lip it was uneven so I put a small piece of metal under the other side to level it out. After you have your transformers just the way you like them, leave the transformers on the board and use a sharpie to make marks through the screw holes on the bottom. After you have marked where the screws will go, remove the transformers and drill holes for them, then put them back on and screw 'em in. 

Step 3: Position the Other Stuff

After securing your transformers, its time to install the switch. I had to cut the ground lug off the switch cause it was in the way, so i removed the screw and cut it off and put the screw in a hole near the top of the switch, i also cut off the two top screw holes. After that, the switch was ready to be put on the board along with the transformers. i bent the bottom two screw holes right at that line so that the switch would be slanted, i think this looks better and it a bit more convenient. I then marked the holes to screw the switch in and drilled them out but you must wire it up before you screw it in. 
First off connect the neutral from the inlet to the bottom lug on the switch. Next connect a wire from the top lug on the switch with a spade connector on the end to connect the capacitor to (you will need to use the capacitor to measure your wire length). Next connect the live from the inlet to the other connector on the capacitor. Then connect the ground to the screw on the switch and another wire to the transformer cores, i just soldered it to the end on the secondary winding. Last thing is to secure everything, I bent a metal bracket from a transformer mount to fit the shape of the inlet and screwed into place to keep it from moving every time I pug and unplug it. I just used super glue to hold the capacitor...   

Step 4: Wire Up the Transformers

Because we are using 120V transformers and I'm going to be powering it off 240V, you will need to wire them in series but you must wire them in phase otherwise you will just get little sparks. This simply means the two wires powering the transformers must be connected to the same side on each primary, look at the picture if you don't understand. 
Connect the neutral and live wires coming off the capacitor to the to either the two left, or the two right leads on the transformer primaries, not one on left and right or vice versa. Connect the two other leads together and that will be it for wiring everything up. 
I used thin steel wire to keep the wires neat and close together.  

Step 5: 240V-120V Outlet Adapter

I don't think anyone will need this part but i wanted to share it with you. The outlet my dad made for the air compressor was close to a regular 120V outlet except one of the prongs was sideways so I had to build my own adapter. 
I got the bottom of a wall wart that still had the prongs on it and i bent one sideways and made it as flat as i could, I then heated up a copper wire and melted it through the plastic for my ground. I got the end of an old extension cord that iv'e been saving for a long time and connected that so i could plug my 120V power cord into it. 

Step 6: More Power

The two transformers alone can give some pretty nice arcs but some resonate capacitors on the output can give some much better arcs. All you need if four high voltage capacitors from the microwaves and wire them in series parallel and connect them to the output and the arcs can be drawn out much longer and also seems to draw less current. You could also just use one capacitor in series with the output but it will burn out pretty quickly. Putting the capacitors in series parallel does not change the over all capacitance but does increase the power they can handle. When drawing arcs, make sure to keep the metal casings on the capacitors touching or the cases will spark to each other.  



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    What an ignorant response...

    I see you're one of the great minds that will help us advance as a species. I pray you don't reproduce nor have already, would be a shame to have someone like you instructing offspring to not ask questions and to not advance ones knowledge of the world around them.

    I truly appreciate your time and consideration


    I've a 230v MOT from an old oven , is it possible to use it single cause i v already 230v primary in it , our electricity city is running on 230v

    in many forums and tuts all uses 2 MOTs 11Ov each so they uses 2 to double the power


    1 reply

    with a 240v primary you just wire them in anti-parallel (to prevent phase cancellation)

    DESPERATELY NEED HELP IMMEDIATELY...I'm having a hard time understanding the science and requirements of building and maintaining a D.I.Y. MOT welder. I have almost everything I need and am clueless but, REALLY want to make one and use it. PLEASE, anyone w/ experience whom could bestow some knowledge upon me...I'd really appreciate it !

    I don't understand why folks (according to my research) can't just draw up SIMPLE & TRULY step by step instruction with, a detailed SIMPLE check-list of any/all materials/equipment needed to successfully build such things.

    Thank you for your time and consideration,
    -The G.O.L

    1 reply

    if you can't understand it then youd probably be better off not messing with it

    in my city is used phase transformers 380v / 220v and Phase-earth voltage is 220V. So here have neutral-phase 220v

    depends solely on the place and power distributor

    lmao ok then is there a way to make one the puts out 200 amps?

    is there a way to make that able to power say a house but stay that small?

    3 replies

    Yeah, If you want to fry every electronic in your house.

    He just vanished

    I don't really got on here that often anymore, that's all.

    hi guys
    nice post about [url=] Hight voltage Transformers [/url]
    keep posting

    hi guys
    nice post about [url=] Hight voltage Transformers [/url]
    keep posting

    they make the wall plugs like that for a reason. in that type your showing in the last picture, both 'prongs' are sideways, or flat, and when the plug itself when it has two sideways prongs, it is supposed to go in a 240V 1 phase outlet.

    The vertical part on the left side indicates that it can handle a good bit of current.

    you should never try to do what you did, because it is dangerous. (but then again, so is this project!!!)

    you can pick up those 240V adapters from a hardware store like Lowes or Home Depot.

    2 replies

    What happened to jimmy

    i think his parents kicked him off youtube. i realy have no idea what-so-ever.

    i like working with mots also but make no mistake they are deadly and the caps are very dangerous,i have been running a six mot stack on my coil for years,but your set up as is very dangerous