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Been watching a lot of videos on youtube about increasing the voltage on Microwave oven transformers!. what i cant undrstand is when people take out the secondry windings of the transformer & replace it with a few turns of 10 gauge wire to increase the power how does it work? as from  what i've seen the 10 gauge wire still has the insulstion on it so how does the current cant get through to produce extra power?. Also what do the shunts do in the workings of the transformer?. can anyone explain this to me in laymans terms!. Thank's, Tezza1.

I want to build an MOT spot welder and ive already cut the wiring out of the transformer but i noticed while doing so i scraped off what seems to be the coloring off the primary.  Will this affect it in any way? Also, i can really tell the power of this transformer? can anyone help?

I'm wondering how to ballast an MOT... I only have 2 and I want to use one as the ballast .. how would I wire it so the other one will work As a ballast.. please no schematics I'm not good with schematics but I am with the basics .. just visually instruct me on how to please .... or with as much detail if you explain in text .. btw one is bigger and the other one is smaller..

Hello everyone, I am looking to get some advise. I am building a Tesla coil and cant really get any transformers other than MOT. I have four MOT with all their other components (Capacitors). What I am asking is can I use these MOT wired up in a certain way and I also read somewhere that I would need to add a component to prevent the MOT's from sucking in too much power. If anyone out there can give me some detailed advise it will be great. I just started the build so pictures are coming soon. Thanks in advance to you all

OK, i just pulled this huge transformer out of a microwave today and was just wondering how on earth to hook it up. Pictures below. so please help. And sorry about the pictures being sideways. The bolts you see are on the bottom.

I looked all over the internet and instructables on how to make a quad Microwave oven transformer stack but all i could find is a schematic  and that is not enough.  there are plenty of instructables on how to make a dual stack but none on a quad also could you show me how to add resonant capacitors

So I have two MOTS and 3 MOC'S (microwave oven capacitors) and I'm wondering how I can wire it to be ballasted and to also have resonance at the same time.. If that's possible.. Because I'd like to have it ballasted but ballasting limits current which in turn gives you smaller arcs so I want to wire it to have resonance so I can have big arcs while still having it ballasted.. Someone please help quick!..    To make it simple I wanna know how to wire two MOTS to be ballasted and also have resonance.. An idea came to mind if I have two MOTS I can wire one to act as an inductive ballast but Idk how to so that's why I came here but I could do that after I figure out from you guys and then maybe I could use one capacitor to act with the inductive ballast and use the capacitor as a second ballast for capacitive ballasting go work along with the inductive ballast.. Anyway Just help me with wiring it to be ballasted and how to wire it to have resonance while ballasted.. And if I can use both the 2nd mot and the capacitor to both work as ballasts at the same time.. Thank you c: No homo but much love if you take your time to help me c; <3 P.s.  Both MOTS are atleast 1000 to 1100 watts and let off 2000 volts minimum and atleast 20 to 30 amps when arcs are being made because my circuit breaker always trips on the wall panel with all the breakers to everything in the house and capacitors are atleast 0.80 to 0.98 uF.. And have a max capacitance of 2000 to 2200 volts minimum.. I can't afford my own circuit breaker to wire to any of the MOTS nor thecapacitor s and can't afford a wall plug thing to wire to a switch either.. So limited on some things..

Hello everyone, I've been working on an arc welder based on instructables like https://www.instructables.com/id/Small-110-volt-arc-welder-NYDG/ but I need some advice. Most tutorials on here suggest two paths to success, either winding two MOTs with as much 10 gauge wire as possible, hoping that the voltage output in series will be close enough to 40V, or using multiple small transformers, also in series. The problem is, all this series stuff really cuts down on the available amperage, so I'm wondering if there's a different way to get high amps and volts simultaneously (obviously without surpassing the available 2400 Watts, energy in = energy out). I think I have a way to make two MOTs which run at low voltage but high amperage also have high voltage. I've made a high frequency circuit to assist in starting an arc, which you can see attached (it works phenomenally, and I've been able to make it run on 1 amp). Since the output on the HF part goes through a torroid at the far right (where it meets the welder's output), would it be possible to wind the torroid with, say, 5:20 turns, to basically take the 120A (10.8V) I get from the parallel-connected MOT transformers and overlay a low-amperage but higher voltage on it, to make arc start/run easier? The welder just won't run at 10.8v, so other than rewinding the secondaries, what about jumping the voltage up a little via the output torroid?

So I have two Mots One is bigger and another is smaller .. just in case .. and they both have the same wattage.. just letting you know just in case that's relevant.. also I have 3 MOCS or Microwave Oven Capacitors .. How Exactly would I wire it for resonance.. please no schematics .. just explain visually or textually but with as much detail as possible ..

I have a crazy idea to make a transformer for a tesla coil useing two MOTs that are exactly the same, Then cutting them so you only have the 2 "E" core sections, Pull off the primary off one, flip the secondry so its out of phase, put the two cores together and clamp them so they cant move. put some extra shunts in to help limit current, hook up the primary to a variac and turn up the power slowly and test the arc. PORK CHOP! pole pig?

Why don't people modify MOT's for high voltage? I just did I left about 3 layers of primary windings, removed the middle coil and the shunts put it back together then submerged it in oil, I also removes a couple of layers of the secondary windings to get rid of the resin so the oil can get in. It worked amazingly I don't understand why people don't do it.

Hey guys I've seen around the net that it's fairly easy to make a spot welder from a micro wave transformer /micro oven transformer. So I was thinking if it's possibly to use the same idea to make a induction furnace? I would like to use it for melting/ casting aluminum (...and possibly metals with a higher melting point... if possible) any idea if it's possible.. and how to?

New Question: Ok, I've done a little more research on this, and it seems that MOTs are just pieces of junk basically. Manufacturers design them to go far into saturation because they don't care how much electrical power is wasted, as long as the transformer is cheap to make. The air gap is probably there just so it's easier to cool with a fan. Now I need to bring this thing out of saturation. There are about 90 turns on this primary, which I want to be the secondary at 30 V. So I would have to wind a new primary with 360 turns of thin wire. That's a lot of work, and a lot of wire. Is it worth it? The other option would be to add turns to the existing primary. This seems more reasonable, but just how much would I need to use to bring it out of saturation? Original Question: So, I'm a physicist (in training) and I know the theory behind transformers, but actual transformers are still pretty mysterious to me. I've found quite a few Instructables and other sites related to MOTs, specifically related to making high current power supplies with them. The problem I'm having is that even when the secondary is open, and indeed when the secondary has been completely removed (and the shunts removed), the primary draws upwards of 10A when connected to mains. To me, this is unacceptable. Transformers should draw significant power only when current is drawn from the secondary. I'm trying to figure out why (specifically) it does this. I've got a variac and the transformer only begins drawing more than about 2 amps once the variac is set to about 90V. This seems like non-ideal behavior to me, but what I know about saturation tells me that the amount of steel the core has is more than enough to stave off saturation at open secondary, but I could be wrong. The only thing I can think of is that the primary coil has about a 1cm air gap on either side of the core. Since the efficiency is related to the magnetic flux, and I'm guessing the area of the air gap is roughly 1/5 of the area of the core, this could cause significant inefficiency. Here's what I want: I want to make a ~30V (possibly with multiple taps) high current supply out of this MOT that draws less than 1 amp when the secondary is open. I tried connecting the mains to the secondary before I removed that and I got about 5 volts on the primary, but I need more than that, and the windings were so saturated with resin I had to just remove the entire secondary. I'm thinking about winding a new primary (using the old primary as the new secondary) with something like 18 gauge wire that would give me 30V. Would this work? What I really need to know is why the existing primary is drawing 10 amps. That's just ridiculous. If I can solve that then the problem is easy. Update: There is a difference between resistive and reactive current, and I know that reactive current actually draws net zero power because it's 90 degrees out of phase with the source voltage. Capacitive and inductive loads do this apparently. Is this the reason for the massive current draw? If so, I might be able to minimize the current draw from the mains line by putting a matched capacitor in parallel with the primary. But this wouldn't stop the transformer from heating up.

Ok so I took a old car inverter and used a 12 volt battery to power it. Then i modified a MOT turning it into a step up transformer with a ratio of 1/4. I was wondering if this is a good way to power my Tesla coil without using my house's mains :D. I plan on testing the finished prodect with the tesla coil tomorrow.

I have modified a MOT to output 10kV as a Tesla coil power supply but when testing I found that there was a very low voltage (maybe 2kV). The primary resistance was measured at 0.2ohm much less than the inductive ballast I've used to current limit. Is the voltage being drawn away from the primary to the ballast? If so how can I resolve this (keep in mind even with the ballast it still needs further current limiting)?

Hello, this is my first post here at Instructables. I will get straight to the point. I plan to build a diy spot welder. However, in most of the diy spot welder projects I have looked at, including Hack a Day and Instructables, a MOT (Microwave Oven Transformer) is used. The secondary is rewound with thicker wire, and the transformer is used to step down voltage and step up current. I have heard that these transformers can supply as much as a kiloamp at very low voltages. However, I do not own a MOT, they are too costly to buy, and I do not want to retrieve one from a microwave because- A) Nobody happens to be throwing away a microwave in my area. B)The guys who own the scrap metal and thrown away appliances will only give me a microwave oven at a hefty price. C)I would prefer to live a very long life, and do not want to gt myself electrocuted poking around the innards of a microwave. SO, I did a thorough search, and found that some people made a welder from a stereo amp transformer. Again, I did not own one, but what I did own was an ultrasound generator that was supposed to drive away rats. After making  bloody inroads into it`s innards, I found a transformer quite a bit larger than the regular step downs. It is 5 cm long, 4 cm wide and 1.7 cm tall.  Input voltage is 220 volt AC from the mains, at 60 hertz. Output is 12 volt AC at a maximum of 300 MA. Speaking from experience would anybody please tell me whether this is suitable for a spot welder? Please ask me for additional information, including pictures, if required. Thank you.

Hello, I have a rewound MOT (230V input and 9-50V output, different custom windings) and I'm wondering why the transformer gets so hot when no load is even connected? Is it normal that MOT's get so hot quickly because the primary impedance is just so low? and how do they fix this problem when the MOT is still inside the microwave oven? Because there, it does need to be able to run for hours. I've read about ballasting the MOT, but I thought that was only for current limiting, when you Are attaching loads on the secondary? Greetings, Electorials

Ive got a issue with my arduino moisture sensor readings because my if and else statments. my else statment will not follow it at all here is my code.. // 11 sen // 7 heater // 4 analog sen int sen = 11; int hOn = 7; int mot = 3; void setup() {   Serial.begin(9600);   pinMode(hOn, OUTPUT);   pinMode(sen, OUTPUT);   pinMode(mot, OUTPUT); } void loop() {   digitalWrite(mot, HIGH);   digitalWrite(hOn, HIGH);   digitalWrite(sen, HIGH);   analogRead(4);   delay(5000);   digitalWrite(sen, LOW);     if (analogRead(4)>=410)   {     Serial.print (analogRead(4));     Serial.print (" Moisture Level Is Bad ");     digitalWrite(hOn, LOW);     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(300000);     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(60000);   }   else if (analogRead(4)<=409)   {     Serial.print (analogRead(4));     Serial.print (" All Is Good ");     digitalWrite(hOn, HIGH);     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(300000);     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(60000);   } } // i have tryed just a plain "else" statment and also another plain "if" statment

Hello i'm making a Spot welding Machine using a microwave transformer i'm removing the secondery coil to replace with 2 rounds of very thick wire for the output . the only problem is the transformer rated for 120V input Will it matter if i connect the primary to 220v ? i'm replacing the secondery anyway ?

Hi, I was reading the Electroforming 'ible https://www.instructables.com/id/Electroforming-an-Iris-Seed-Pod/ and I have a couple of questions: 1)  It says you need an 18 amp digital rectifier. However in step 13 it says "Check the amp and voltage setting, they should both be at or below 1".  Why do you need an 18 amp rectifier if you only need less than 1 volt and 1 amp? 2)  Is it possible to build some sort of a suitable rectifier from scrapped microwaves?  I know people wind a 10 gauge secondary into the MW transformer to make welders, so can it be done for electroplating too? Thanks!

Hello, I'm busy with making a spot welder from a MOT (microwave oven transformer), but I'm not really sure why and how to ground the MOT. In the picture you can see that a wire from the high voltage coil is connected to the casing which I find to be Really odd. That wire is not really a problem since I'm going to remove the secondary windings, but I'm just interested in an answer to that. Another question is, is it necessary (for performance) to have the MOT grounded? or is it Only for safety that the casing needs to be grounded? (no matter what the answer is, I'm still going to ground it, so it's not necessary to have safety discussions here) thanks in advance, Electorials

Hi, I just found a MOT from a discarded microwave and was wondering if I rewound the secondary winding with a thicker wire (to get about 12V or whatever i need) would this be a good power supply for like an amp or other stuff (well it's a simple transformer (or is it?) i don't see why it wouldn't be, but before i mess with it i thought why not ask.) Also there was a sticker on teh microwave that said 700W and i wasn't sure if that is the power of the transformer or the Magnetron. Thanks in advance. Oh, and sorry bout me bad Engrish.

Hey guys i have made this program but im a little concerned because my values from my moisture sensor jump around quite a bit and if the sensor values are wrong for to long it may keep the heaters on for too long which can cause a fire i did use an if statment instead of while im just trying differnt ways here is my code... #include LiquidCrystal lcd(7,8,9,10,11,12); int sen = 5; int hOn = 6; int mot = 3; void setup() {   Serial.begin(9600);   lcd.begin(16,2);   pinMode(hOn, OUTPUT);   pinMode(sen, OUTPUT);   pinMode(mot, OUTPUT);   lcd.print("Start Up");   lcd.setCursor(0,1);   lcd.print("Complete"); } void loop() {   digitalWrite(hOn, HIGH);   digitalWrite(mot, HIGH);   digitalWrite(sen, HIGH);   analogRead(4);   delay(5000);   digitalWrite(sen, LOW);     int val = analogRead(4);   int good = 451;   int bad = 450;   lcd.clear();    while(val <= bad)   {     lcd.clear();     lcd.setCursor(0,0);     lcd.print("Heaters On.");     lcd.setCursor(0,1);     lcd.print(val);     lcd.setCursor(4,1);     lcd.print("UpT:");     lcd.print(millis()/1000);     digitalWrite(hOn, LOW);     Serial.print (val);     Serial.println (" Moisture Level Is Bad ");     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(300000);     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(60000);   }   while(val >= good)   {     lcd.clear();     lcd.setCursor(0,0);     lcd.print("Heaters Off.");     lcd.setCursor(0,1);     lcd.print(val);     lcd.setCursor(4,1);     lcd.print("UpT:");     lcd.print(millis()/1000);     Serial.print (val);     Serial.println (" All Is Good ");     digitalWrite(hOn, HIGH);     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(300000);     digitalWrite(mot, LOW);     delay(120000);     digitalWrite(mot, HIGH);     delay(60000);   } }

I have just bought a 4 stack MOT transformer in a case and oil filled it says 8.6kv on it but no idea of amperage, I have a large variable ballast and hooked it up to my test jacobs ladder and it pulls about 10amp and really fires the ladder well. My coil has a 6inch by 29inch winding on the secondary and a Synchronous spark gap (200bps) but I cant seem to get a decent spark off it I have an MMC of 44.0nF @20kv at the moment 

Can you melt steel scraps in a heat resistant pot hot enough to mold or pour with a rewired MOT? What if you put multiple MOTs in series/parallel? how could you make into three phase (i want to know weather this works or not)?

Ok, well I took apart 4 Microwave Ovens and I took the MOT and Capacitors. I already built the secondary with a 4" PVC pipe about 4 feet tall and I bought the primary (copper tube). I am using a fan from MO for my spark gap so it will rotate and cool at the same time. Want some advise on this build before i post it as an instructable. I read somewhere that I need to add something to block MOT's from sucking in too much current. Any help would be great. Thanks

I asked a similar question https://www.instructables.com/answers/How-to-improve-tesla-coil-/ and I still didn't managed to get a spark. I want the simplest way to build and power this tesla coil  Now I have : -5 layden jars -1 MMC -1 primary 5t -1sec 500t -1 zvs (dc out at 30kv) -1 ignition coil -5 timers -1 MOT -2 capacitors for MOT at 0.98uF -2 diodes for MOT

I FRIED my MOT and im looking for some old microwaves, i checked all the junk yards, but couldn't find any. Any suggestions?

So i've been into hv stuff for years,currently engineering undergraduate, just never did anything practical. So recently we got a new microwave, therefore old microwave= junkyard ^_^. Anyway, i acquired a MOT i also took the capacitor and diode, and the magnetron (never know when you could crave instant cooked meat ^_^ kidding). Then a few days later (last week) someone left a computer monitor outside on the sidewalk, which equals source of flyback ^_^. clearly someone up there wants me to play around with hv (or is it someone down there..?) and so thats how i  came into possession of a flyback. i could have had one a while back, we had a big tv, which had one of the big old flybacks which are way better than modern ones, but this is before i knew about flybacks and so i dismissed it as some large junk...to this day im still slapping my forehead over the fact that i let that go... Naturally, i have a few questions: 1. I hooked up the mot to mains (deadly i know) but the arcs were insane. i tried ballasting it with a cfl bulb, 15 watts, however, when connected the mot did nothing. touching the hv to ground only made the cfl brighter. why? 2. i pulled the flyback with the circuit, i actually took out the whole board from the computer monitor. how can i use this as a driver? i know i could pull components out and make one but seems to me whats already there would be good enough. 3. Found out i can use a cfl to drive the flyback, can i also use this for the mot? one other thing, i was thinking of using the mains transformer (torriodal transformer) from the monitor to power the mot and/or flyback, using it as a step-up or step-down transformer. Is this possible with the flyback? Thanks, and sorry for the loong question im just excited ^_^

Can I modify a Microwave Oven Transformer into high voltage? I had a MOT. secondary coil: 2kV output I heard some people in internet were modify the MOT into high current Can I modify the MOT Primary Coil into a few turns. Just like this formula : Vs/Vp = Ns/Np The original is : Vs/Vp = Ns/Np      2000/220 = 2000/220 In my imagine : 30 turns heavy primay New one : Vs/Vp = Ns/Np       Vs/220 = 2000/30     Vs=14 666.6667 Can I do this?????????????????????

I recently got two old microwaves from a junk yard and wanted to build an arc welder with its transformers by connecting both in series and getting an output of around 40V all together. But when I open the microwave instead finding the big chunky laminated iron core transformer as shown by many youtube videos, i found a small weird looking transformers instead. ( as shown in the pictures) I read somewhere stating that the primary coil should at least have 1 turn per volt. However, this transformer only had around 17 turns in the primary. The core was also not laminated and it had a copper wire holding it in place. The primary coil was made of a thick litz wire and the secondary was a very thin wire. Anyhow, I still continued the project and I experimented with one first. I use the same primary and made my own copper wire for the secondary. I made the secondary by using thick copper wire which I found in some antenna wire and I stacked it up and twisted it and put a heat shrink tube on it. Base on a few tutorials i saw i need an output of 20V from each transformer coming from an input of 240V AC. So with 17 turns in the primary i need around 1.5 turns in the secondary. When i finished everything and connected it to the power supply, it vibrated for awhile and then blew the 13A fuse in the plug. So i added a light bulb in series hoping to increase the resistance and reduce the current but this time nothing happen and it didn't even vibrate but the bulb did light up. I think its because the primary coil has a resistance around 5 ohm and the bulb have resistance of 100 ohm so the potential differences is very low on the primary coil. I am not sure why isn't it working. Please help me as i can't find any tutorials on how to make a welder with this form of transformer. There were no other transformer in the microwave so this was definitely the main transformer. Is the problem because it has too little turns in the primary coil or it has too low resistance? I don't know please help me. Thank you!!

I have two microwave oven transformers (MOTs) that I am currently working on, and I have taken one of them apart to make sure of the wiring of the coils. I am fairly confident in the wiring of the whole system. I have the original primary and secondary coils, both made of copper. The transformer is one of the larger ones I have seen, and its wattage at about 1000W. I know it is not popping the breaker because the hum is always on. I have read through many of the instructables out there about MOT's, so I understand it pretty thoroughly, but the arcs on the instructables I've seen are several inches long, and my arcs are about half a millimeter. I really wouldn't call it an arc at all.  I have the common wall output of 110 VAC, 60 Hz going into the primary coil, and the ground is attached to the MOT block itself. One of the secondary output wires is connected to a capacitor bank of 3 MOC's in series, and I have the other output on the end of a PVC pipe which I touch to the opposite end of the capacitor bank. What am I doing wrong? 

I just want to be a 100% sure that i did this right before i plug this thing in, because i don't want to kill the transformers or myself :D So if you guys could confirm that i did this right (or not and if not why) i might feel a bit more comfortable :) thanks for all the help! love this community and tesla coils! explanation: powersupply: 2 mots with the secondaries placed in series while the primaries are paralleled ballast: 1 mot with the secondary shorted (both ends to the core) and grounded to the mains ground the neutral wire from the mains is directly connected to the 2motstacks first primary while the hot wire from the mains is connected to the ballast it's primary and then to the 2motstacks first primary finally i taped one 2000V terminal to the wooden box and the other 2000v terminal to a 4ft PVC pipe that acts as a chickenstick Did i do this correctly? here is the picture with explanation from what i did

I just made a 3 phase MOT power supply and it's fun to play with (while being safe) but every time I use both phases it trips the breaker after only 2 arcs, sometimes it trips just from plugin it in, I am using a PFC cap on the mains side as well as a long extension cord, I have one of the transformers ballasted, and one of them has 3 MOC's in series on its output, the breaker can handle one of them just fine...for a little while. Is there any thing else I can do besides buying a bigger breaker switch? I'd say mine is 20A but i dont know for sure.  Every time I draw arcs from my MOT it heats up really fast really hot, I am using the same setup as above , the only thing I can think of is to submerge it in oil but I dont want to do that because I'll want to make changes to it. What makes it different from a welding transformer in that they are made to draw arcs from but when you draw an arc from a MOT its a direct short and will eventually destroy the transformer?

I want to know how to make the smallest grappling hook gun and the mot powerful

For shooting rabbits and squirels

Im having trouble generating any kind of plasma and i guess not fully understanding this. Heres my setup: A metal pot with a Plexiglas lid as vacuum chamber. a pressure gauge on top A vacuum chamber A MOT as the power supply. Dont have equipment to measure high voltage but id guess around 2KVAC as thats what i understand is standard Two terminals about 2 inches apart inside of the chamber made from copper. one coming from the top, one from the bottom.  I hook up the terminals , hear the nice MOT buzz, but nothing happens inside of the chamber. The mot has been tested and does work.  Any clue or direction to point me in?

I just built a beefed up ZVS driver to handle a large continuous current, however, I now lack a power supply that will allow me to reach its full potential. The biggest thing aside from my variac that I have is two xbox power supplies in series (24V 29A). I would like something around 40-50V with at least 5A. I could rewire a mot which would take a very long time and weigh a lot so if anyone has any schematics or pointers on how to make one electronically it would be much appreciated! 

I also plan to use L298NH H-Bridge.

Where is power wires in the first part not the motor's ones?

I think it would be better if the link to the forums went to the mots recent topics only, not the most recent replies. Comments? Agree? Other suggestions?

How to transfer static energy to electrostatic motor from ballon to make it rotate, and which type of wire. use to transfer charge

I want to buy some resistor capacitors and some ics anybody has some ideas??

Do you cast upstream or downstream etc? Any other stuff i will kneed to know.