Introduction: How To: Resonant Microwave Oven Transformer High Voltage Supply.

Picture of How To: Resonant Microwave Oven Transformer High Voltage Supply.

Okay first of all i feel i should give a little disclaimer. Microwave oven transformers are indeed LETHAL the current and voltage that they put out is more then enough to kill you, the voltage and current they run off will quite happily kill YOU! Microwave oven capacitors Hold a strong charge for quite some time, do not attempt to alter anything or do anything at all without discharging all capacitors! This is serious stuff, but its also fun stuff so lets keep it safe and keep is fun. we want to be alive, not just live. Okay? good...

Now Microwave oven transformers which i will refer to from here on in as MOT's have been a keystone for beginners and advanced high voltage hobbyists alike for as long as I personally can remember. And as fun and as simple as these deadly but wonderfully robust transformers are, it is possible to get more technical into them. In future instructables that I shall be making I shall cover such things as MOT welders, High current for HHO production, MOT PSU's capable of a kilowatt of power. In this instructable however i shall detail the steps behind making measly MOT arcs into HUGE arcs utilising the magic of resonance (not real magic) And then furthering that with a little thing call power factor correction which i will refer to as PFC and ballasting which i will refer to as.. ballasting. 



Also as this is my first instructable constructive criticism and feedback is most certainly welcome. please no negativity :)

Step 1: Obtaining the Parts!

Picture of Obtaining the Parts!

 Alrighty then! For the Ultimate MOT powered arcing set-up you will first need to components to put it together. and a mind dead set on safety! for without one of those, you will wind up dead set on the floor!

Now then, I shall list the components...  now:

1) You will need two or three MOT's, Three is better as you can use one as ballast.

2) An appliance that you may use as ballasting for your transformers. A hair dryer or a toaster works anything like that, this is only if you can only find two MOT's

3) 4 Microwave oven capacitors which i shall refer to as MOC's (These are the key in the resonant side of things)

4) A motor start capacitor or something of similiar value. to use as a PFC capacitor, for >230 Volts use about 20uf and above 300 Volts. and for the 120 Volt people use 80uf rated for >200 Volts. Must be AC type capacitors!

5) A 10-15 amp Circuit Breaker ( For Safety)

6) A 120-240 Volt Rated switch

7) Lots of wire including a 3 pin grounded wall plug.

8) A 2 foot long (minimum) Piece of PVC or insulating electrical conduit ( To be used as a 'chicken stick' )

9) A Wooden Base for it to go on!

10) Dark sunglasses or a welders mask! Arcs are bright! and will damage your eyes!

11) most importantly, common sense!

Also as a heads up, the wire, the MOC's, the MOT's and the grounded plug can all be salvaged from a microwave. Be sure to strip it entirely, there's two strong magnets in the magnetron there's diodes to be used in a MOT Doubler, there's switches fuses resistors lots of wonderful stuff!

The picture below is my current arcing set-up. Not configured for drawing long resonant arcs but shorter stable arcs. I will add a video of this soon. two of the MOT's are for ballast.

Step 2: Putting It Together!

Picture of Putting It Together!

 Yay the fun part. now I shall continue to give you a brief (or detailed depending on how energetic im feeling as its currently 2am!) outline of the set-up along with a labelled picture and a schematic.
For starters or as...

Step 1) get your base whatever its made of and place your MOT's on it two to three if you have three put two side by side not touching, and one in front of them, if you have two just put them together side by side not touching each other. then screw them onto the board to hold them in place.
Step 2) Wire your switch, circuit breaker, and the plug that's going into mains supply together. The "hot" or "live" wire of mains shall be connected in series with your circuit breaker, then to your switch, then to you PFC capacitors but ill cover the PFC later. Then the neutral line goes straight to the PFC, and last but not least the Ground or earth line connects directly to your MOT's Ground connection and if you have anything made of metal Eg. your switch box, GROUND IT!

Step 3) Power factor correction. your power factor correction capacitors will be in parallel with your Live and neutral lines, neutral down one side and live down the other, then to your MOT's For my PFC instead of the motor start capacitor im using 3 MOC's in parallel with mains connected to my MOT's. 

Step 4) Connecting the MOT's. First off to power up a MOT you need to identify the primary winding. the primary will most likely be on the bottom close to a base plate. and have two spade lug connections next to each other, with thicker wire and less of it. now to connecting it. now if its just one MOT you can connect the power to it on the primary either way. and it will work fine. But with two MOT's you will have the input in parallel and in phase, so live will be connected to the same side on both MOT's so they both phase in which will allow arcs to be drawn rather then short bursts of flame.

Step 5) Wiring the Output. First you need to identify the secondary windings, the secondary is obviously the one that isn't your primary as there's only two windings. its got thinner wire and lots of it.  There is two parts to it. the High voltage out which is a single spade lug connection on one side or the other. and then ground which is grounded to the Metal core of the transformer itself. so if you were to power up a MOT and connected the high voltage out connection to the transformer it would arc. Okay now connect one of the spade lugs from one MOT and Connect it to the base of the next MOT, This puts them in series so the high voltage out of one will arc to the transformer core of the other.

Step 6) Ballasting. Get your last or third MOT and connect a single wire to short out the primary winding. then Get the Ground end of your two MOT's and connect that to the secondary out lead of your ballast MOT.  and connect a scrap piece of wire off the Base of your ballast MOT as that is where you will draw arcs from.

Step 7) Resonant Capacitors. Now you will Need your MOC's get four of them and series two parallel sets of 2. and attach one end to your High voltage out of your two MOT's then attach a large length of wire to the other end of your MOC's and attach that to your Insulating pipe for your chicken stick. you will use this to draw your arcs.

Step 8) Now it should be all wired up. Plug it in, turn on all your switches and Draw some hefty arcs! WEAR EYE PROTECTION! ITS WORSE FOR YOUR EYES THEN WATCHING SOMEONE WELD!

Step 3: Final Product!

 Finished! im half asleep now so if i missed anything or if theres anything to add dont hesitate to tell me! Thanks!



69buickgs (author)2015-09-02

What you are calling the secondary and primary are backwards. The secondary is the bottom, line-voltage winding and the primary is the top, stepped-up high voltage.

hydranix (author)69buickgs2017-06-06

Primary is input, secondary is output. Simple as that.


Free kill (author)2017-05-04

can i use mains dimming to make it 0-4kv

hydranix (author)Free kill2017-06-06

No, do not do this, you shouldn't try to regulated a MOT's output voltage by regulating the input voltage.

Grooby (author)2010-03-16

Whats The output Voltage Like or is the current that is creating the huge arc?
And what could you use it for?

HazzWold1993 (author)Grooby2010-03-17

 The output voltage is 2000 Volts AC either side so a total 4000 volts AC.
The current is what makes the burning arcs, theres aprox 1-2 amperes of current. I currently have a 10 MOT stack which draws over 150 Amps from the line.

CarsonC9 (author)HazzWold19932017-04-26

10 MOTs and 150 amps?! That's crazy! But also amazing! Do you have a dedicated circuit breaker or something for that? For my system, which can supply 60 amps, I took three different 20 amp circuits that are on the same 120v phase and have a box that puts them together, works good for powering 3 MOTs at once, but I primarily have 2 powered and one as a ballast, along with 4 capacitors for resonance. I'd love to hear how your system is powered.

Plasmana (author)HazzWold19932010-06-18

Hundred and fifty amps form the mains? That is a hell alot man, otherwise, great project. I am going to build one of those beast after I get my hands on one more microwave. :)

HazzWold1993 (author)Plasmana2010-06-18

Awesome :)

infinity11 (author)2013-02-05

is it possible to vary the output from this device. e.g. 0-50kv

aclark17 (author)infinity112016-12-09

You could use a voltage multiplier, BurningSunTech has a great instructable on here to make one, the amperage is only like 350mA, but you wouldn't want 50kV with this much amperage anyway unless you're trying to die lol

shomas (author)infinity112015-08-05

Although it might limit the current carrying capacity, the easiest way to vary the output is to vary the input with a variac. Your unlikely to reach 50kV unless you hook up more than twenty or more MOTs with their secondary windings in series and primary windings in parallel.

Using more MOTs would also mean using more MOCs in series to handle the extra voltage and parallel to increase its capacitance google capacitors in series and parallel to design the specs of your system. I would be concerned about the voltage build up on the ballast as it will arc when driven at too high of a voltage, adding several ballast in series will distribute the voltage difference

aclark17 made it! (author)2016-12-09

Yaaaaaay! I love this thing, I did a little Jacob's Ladder thing with it:

ValK6 (author)2015-12-12

Is there any way to modify or reverse coils polarities such secondary as primary and primary to secondary to reach 350 volt and 5 Amperes??

Any bright ideas rather making pointless sparks..

jbrittain2 (author)ValK62016-09-19

Yes use them to send power out to your building thats far off.. 120+120 to 3200+3200 to overhead or underground lines (maybe safer underground) to thr next transformers at thr building..3200+3200 to 120+120 and viola you have single phase 240 volts at the shack with almost no loss

jbrittain2 (author)2016-09-19

Just though to metion those transformers would be handy to send power far off to your building in the woods or on a farm. Stack em up ans get as much mains as far as you need without the utility coming to drop a separate line at the site..

jamesp157 (author)2015-12-28

can i convert that into 12-24 VDC?


ValK6 (author)2015-12-12

Is there any way to modify such transformer to 350 volt under 5 Amperes load??

eXtremeSomething (author)2011-08-18

Now connect it back up to a magnetron in a microwave, "DINNERS READY"

shomas (author)eXtremeSomething2015-08-05

How fast a mirowave cooks depends in large part depends on how many watts it draws. having two transformers in parallel to the main draws about twice the power.

MX_Love (author)2014-07-18

How could we get DC out put out of it ? I already have some high voltage diods and I know we need a watson bridge in order to rectify the alternative current and capacitors, but the problem is that I don't know what kind of capacitor/capacitors should I use?How many farads and how many volts they should be able to tolerate for such purpose?

shomas (author)MX_Love2015-08-05

How could we get DC out put out of it

You connect the input of a full-wave bridge rectify to the AC High voltage output. One should double check the rated voltage of the diodes. If nessesary, each leg of the bridge can have more than one diode pointing in the same direction. Four 600 volt diodes in series will protect up to 2,400 volts.

mrm1899 (author)2015-04-11

Do your MOTs even lift?

sheydon (author)2014-09-28

Hi There, Thanks for your efforts in putting together this tutorial. I was just wondering where your final video went to?

Below is a link to my Tesla coil FB page

I just build a 4 MOT power supply to run my Tesla coil, but I'm having some challenges that I didn't experience while using a 15KV 60mA NST. If you are interested, I lay out the whole process there in a recent post. Perhaps you could assist in helping me figure out why the 4 MOT power supply isn't running my coil. Thanks!

crazy-blender (author)2013-03-15

how do I ground the cases. Do I ground them together or apart because if I ground both of them to the same plug will the power frome the HV out from one transformer goes
to the case of the other transformer and into its ground connection but since the 2 transfomers cases are grounded to the same plug it might just jump across. What should I do about this problem and how do I fix it. Right now I do not have the cases grounded. Please put the youtube video back up for me and the community please hazzwold1993.

KylerKraus (author)2013-03-10

please put a video in "this video does not exist"

crazy-blender (author)2013-02-22

Can you use 2 Microwave Oven Capacitors (i only have 2)

CHOCOLATEmeter (author)2012-06-13

theres a problem there is no two live wires used , to my knowledge you use a ground and a live phase for 120v

aloving95 (author)2011-12-15

What is the Purpose of the PFC capacitor? whould it still work if i didn't use one?

aclark17 (author)2011-11-02

Im not sure about step 4, connect the "ground end" of the two MOTs? Do you mean to say that HV out of one goes to base, then either base or HV out of 2nd hooks up to the HV out of the ballast, and you draw arcs from the wire connected to the base of the ballast? Is that correct?

aclark17 (author)aclark172011-11-25

I got it, no problem! It works fantastically, and Ive been having great fun seeing which types of metals make which colors, though its difficult to see sometimes because of the need for eye protection. So far as I can tell, copper is green, titanium is either a bright white or a blue, aluminum.... yellow I think. Anyways, great instructable!!! Thanks so much!

qola (author)2011-05-15

and then what kind of aplications would you use it to, burning air, cooking foot, making bbq, xD any other Suggestions ??? let me know :-D

Jimmy Proton (author)2011-03-31

I thought you weren't supposed to continuously run start capacitors, I have one that I found in the junkyard and have nothing to do with it so I'll use it for this.

Nah, they aren't made for pulse discharge, but they handle the mains continuous cycle fairly well.

Pyrocloud (author)2011-03-12

Any idea if this would make a suitable powersupply for a tesla coil?

HazzWold1993 (author)Pyrocloud2011-03-12

it would work yes, the spark gap would be a bit finicky though with such a low voltage 2-4kv....

Pyrocloud (author)HazzWold19932011-03-12

ah cool, so in theory it should work better if i made a larger stack for a higher voltage

HazzWold1993 (author)Pyrocloud2011-03-12

Yes, you will find many people on the internet use a "Quad stack" for around 8Kv, but for the size, you would need to make a very large Tesla coil to make it worthwhile. And the quad stack would need ballasting, and to be under oil to prevent flash-over.

Jimmy Proton (author)2010-09-17

is the PFC capacitor also a MOC?

3 MOCs in parallel make for good PFC


TheDoci (author)2010-08-23

i dident have a good resunlt from this. may be that i only used 1 mot or 1 moc or that i basasted it on the primary. but when i dident use the moc it gave me 2X the output it used too, it melted my hotstik. :(. but i fixd it. it seams that resonating it on the primary sid is the way to go for me.

Bob_144 (author)2010-04-28

Could this be modified to use as a basis for a plasma torch? And if so what would need to be done?

HazzWold1993 (author)Bob_1442010-04-28

Plasma torch?
no idea, sorry..

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