OH MY GOD!!!!! WOW!!! HE SPEAKS!!! THANK YOU!! THANK YOU, THANK YOU, THANK YOU, for not just playing shit music, or typing words on the screen during editing!!! By far. The ONLY REAL Rewinding Transformers Video IVE SEEN!!!! WOW!!! GREAT JOB, JUST BECAUSE YOU SPEAK!!!! And I bet I know why you speak. Because you actually know what you're doing and why it works. Not just "HOW" to do it, like most of the hacks out there making videos with music and text that just tell you DO THIS!!! And don't explain a thing. YOU KNOW WHAT YOURE DOING@@@ YAY!!!! BEST VIDEO!!!
These transformers are no good for this purpose, they are not designed to run continuously and they are overdriven to keep cost and size down, a transformer designed for 800 - 1000w continuous duty cycle would need o be twice this size.. Driving the transformer in this way means it has a very high idle current of usually over an amp or even more but even at 1A 240v thats 240w being dissipated needles to say they get HOT fast even with no load...
It appears this is mostly a mechanical how-to. Maybe it helps if I add some electrical comments. First, there are some manufacturer data sheets for transformer sizing. Generally the more power required, the heavier the core becomes, KEEPING the line frequency the same. A higher frequency allows reduced weight, up to a limit. Above some 400 Hz, you need better (thinner laminations and those insulated from each other, also no more welds) materials and above 20 kHz you likely need to switch over to ferrites. Then, the optimum tradeoff between core and winding heat losses comes at near 1:1 ratio of the iron cross area and the window (core space) cross area. The winding formula is n = U/(4.44 f b A), where n is number of turns, U is the applied RMS voltage, f is the frequency, b is the allowed peak magnetic field and A is the iron cross section. All these in the metric system, i.e., the A is in square meters and b is in teslas. The b depends on the iron quality and varies from 1.2 to 1.3 for most practical materials and some 1.55 to 1.7 for some crystal oriented materials. Then, about the shunts - they are actually causing leakage magnetic field ("radiation"). Their purpose in the microwave oven is to LIMIT the current. As such, they also cause additional heating of the transformer. Along with too few turns in the primary, they are a cause of higher primary current (which was a concern in another comment). For a bench power supply, where you should do current limit in electronics, you should replace those shunts with some wood or plastic strips. That would improve your efficiency, although it would increase your INRUSH current, as the limiting action is discarded. I hope this info still reaches some people who might benefit from it.
Pellervo Kaskinen thanks for the info , for anything related to laminate I use the 42 constant, which is the Ae area effective divided by 42 I.e 42/ Ae = Tpv Tpv = turns per volt I have tested this extensively and can not fault it including ‘blind’ tests where I used it to predict the turns then unwind various ‘consumer’ windings to find it accurate, even on large turn numbers, however this equivalent may help with trying to derive a new ‘constant’ for various crystal hybrids so thank you . I don’t have my book here immediately but yes the primary of a microwave Transformer has missing meters worth of inductor based both on the 42 constant and on me predicting then unwinding. I believe it was missing many meters. This and other factors contribute to the excessive heat and energy loss that these lovable and famous devices radiate. Regards.
I have a question for you since you seem electrically inclined. I'm looking to rewind one of these transformers for an even higher voltage by grinding off the weld and pulling the "E" "I" sections apart to access the core. I'm wanting to build a secondary out of 32 AWG wire with about 32000 turns to get roughly 30000v at 30mA. Will this turn count be sufficient? Assume I take the necessary precautions such as yellow tape bettween layers, in addition it will be submerged in mineral oil. Supply power will be fed to a variac and the output of the variac to a bridge rectifier (no capacitors) with a 15amp fuse that feeds the primary winding which will be kept untouched. Will such a setup work?
I used to rewind small transformers when I was teenager back to 30 plus years ago. This video just let me recall all the steps I encountered like cutting punching measursing guessing patching... I very much enjoyed the work I did. Thank you very much and great work you have acomplished.
go learn what is ,gauss, maxwell ,core properties, winding ration,core size,constant numbers, a lot of formulas, hz, and so then play w/transformers ,MOT THEY ARE JUNK ,JUNK,JUNK,if you hookup a oscilloscope on the secondary side after you rewind this thing tel me what kind of sin wave you see on the oscilloscope ,HO GOD you do not want to see another MOT again ,I work for transformer companies 40 years wind this things ,i love them when they are design the right way
less time. What is being demonstrated here is what can be done “on the cheap”. Ok, you’re not going to run your laptop off it but it would be fine for running an electric motor and other things that don’t need a clean supply. I am making one to put out around 48 volts DC to power 3 other MOT’s that will be turned into an electromagnetic chuck. Where does the average bloke like me get the parts to build a “proper” transformer and how much would that cost. You say they are junk BUT there are a lot of tutorials on RUclips showing lots of successful projects being made from them. To be honest you came across as a bit of a smart arse in your reply. We are not building professional transformers here we are using almost free parts to make something useful. It’s called a hobby. I have worked with automotive suspension but when someone builds a billy cart I don’t tell them to go learn about steering geometry, toe in, caster angles, camber angles first and then play with steering and that the crappy little wheels they are using are JUNK, JUNK, JUNK. It’s just a hobby mate. Who cares as long as it works and no body gets hurt. An oscilloscope? You have got to be fucking joking. Most blokes are just building stuff with these things in their shed. I see it fairly regularly on videos where the “PRO’s” chime in, get all technical and confuse the shit out of the average bloke trying to learn or make something. You have added nothing positive to the subject. All you have done is succeeded in big noting yourself as an expert and putting everyone else down. We all know MOT’s are junk, that’s why they get thrown away. Why don’t you post a video and show us all how we can make a proper transformer in our own garage for next to nothing. Now that would be helpful.
You need to remove those shunts & NOT HAVE THEM IN THE FINAL TRANSFORMER. (If you want mechanical support, put in wood sticks instead.) If you leave them in, the transformer's output will be "wimpy" & collapse when load is put on.
@@paulcohen1555 The "gap" is filled with iron laminations, just like the rest of the frame. This provides a "short circuit" path for the flux. In "ordinary" transformer, you want ALL the magnetic flux to loop through BOTH the primary & the secondary windings. Any flux that "short-circuits" & does not link both causes "leakage inductance". This inductance causes the output voltage to sag when the transformer is loaded. But "microwave oven transformer" is NOT a PURE transformer. The leakage inductance resonates with the capacitor that is series-connected, & these are connected to the tube. This causes the output voltage to rise much higher then the turns-ratio calculations would indicate. The voltage rises until those magnetic shunts saturate, limiting & regulating the current feed to the microwave tube. (Microwave tube "doesn't know when to quit". It will draw current until it blows up if it were not for this limiting mechanism!) When making "ordinary transformer" from microwave transformer, both the capacitor & the magnetic shunts should be removed, as this regulation is not wanted.
MOTs are made as cheaply as possible and are NOT meant for continuous service...the idle current is way too high due to the absolute minimum number of windings in the primary, you need to add 10 to 20 turns in series with the primary for continuous service which will reduce the idle current a lot. Also it is way easier to use an angle grinder to grind off the welds holding the "I" and "E" sections together and then push the primary off in one piece, you can then reuse this wire for something else...MOTs are great for making DIY transformers, light dimming chokes (even variable with adjustable "I" section gap, I have even made audio output and speaker impedance matching autotransformers with them...
Great vid bro. Thanks. Just a add on, for those who need a 2xVAC with center tap, just double the wire turns and pull a tap at half the turns. Of course wire diameter will limit the possible number of turn. One can use enamelled wire instead of PVC insulated to lower the overall wire area necessary.
With the size wire you are using for the secondary, I would watch for excessive heating, even at 10 amps. Remember, the normal current rating for hookup wire is in free space where it is cooled. When you put it in a tight coil, it can't cool as easily. Use larger wire with thinner, higher temperature insulation, less heat. Play it safe.
That is definitely the wrong type of wire,enameled wire is best,not worth taking short cuts.Very dangerous stuff your playing with.Transformers heat up a bit so you have to think about the long term usage.Think safety always. Good luck!!
I just wanted a bright flashlight... I learned about flashlights, which led me to batteries, which led me to power packs, which led me to battery balancing, which led me to variable power supplies, which led me to "make your own PS", which led me to transformers... here I am learning about how to make your own transformer... where am I going from here? How to harness the power of the sun to power your power supply? I feel like I'm a in a free fall... I just wanted a bright flashlight...
This video is boring and aimless which is bad. But it's also totally wrong from a physics perspective, which is unforgivable. You clearly have no idea what the shunts are there for, so you put them back: possibly the daftest thing you could do.
After removing the secondary coil I tested the primary using 240V. After 30 mins. the temperature had risen to just under 100C. That's no load whatsoever. The primary uses around 70Watts no load, this may not sound much but it's all going into that small primary. The only real answer is to add more turns to the primary but that's messing about with mains Volts, unless you really know what you are doing make sure your will is up to date. It did seem to stabilise at around 100C but what happens when the secondary is used for half an hour I have not yet tested. 'China Syndrome' ? - 'Frying Tonight' ?
This is a bit late, hopefully you are still monitoring comments: is there a non-destructive way to determine the number of turns on the primary in order to match the secondary to it? I want to wind a 1:1 transformer to use in my shop for isolation. I would use good quality magnet wire of the same size - shouldn't you use proper insulation rather than masking tape? I've seen Nomex paper insulation used before. Wonder where to get that? Nice tutorial.
This reply is even later 😅 ... The easiest way is to locate two *_identical_* MOTs, and use an angle grinder to cut the 2 welds that hold the top onto the H lamination. Drive the secondary windings out then hammer the primary out of one transformer using wood blocks. Refit both primary windings into one core, then weld the lid back on. .... Things to note: 1. Modern MOTs use aluminium for the primary windings, which needs to be thicker than copper for a given power level. . 2. Microwave transformers are NOT designed for continuous use and have huge power losses (even with no load). This is because of too little steel in the core. So they really are not good for use in proper long term operation. . 3. The secondary of a 1:1 isolated transformer may need more windings that the primary. This is to correct two sets of voltage sag under load. . 4. Almost all MOTs have a primary with the same number of turns as the rated mains line voltage. So a 110V transformer will have 110 turns, a 230V transformer will be the same sized core with 230 turns of thinner wire, etc. . 5. To accurately work out the quantity of turns, wind a test then do math. Start with (say) 20 turns, measure AC Voltage, then divide by 20 to get the resultant "volts per turn". Then finally, wind your calculated quantity on but leave it long until you test voltage again and add/remove as needed to hit your target voltage. . 6. Use an accurate True RMS multimeter. Cheap ones (especiall if not true RMS) will give you strange readings that will skew your calculations.
Just a few hour ago, I got rid of the secondary winding painfully. Then I removed the shunts because they helped protect the primary winding while drilling and hammering the secondary winding. By the way the windings are Aluminum, so be very careful not to damage the primary as its not easy to repair or solder. The outer surface of the primary winding got a bit of a scratch, it's dangerous it touching while connected to power. So I covered it with lacquer.
I question that.i did this on two different transformers.with same # of turns as you.transformer got smokin hot from the constant 4 to 5a load on primary.dont buy it at all,show me the line current on pri. With no load secondary...perhaps you cut the welds on the iron and changed laminations.these transformers are saturated on core.
I just finished cutting the secondary winding out of a transformer. I am following your directions for the winding. I want to make a 24 volt- 10 amp unit to power a CNC machine. I have all the parts except a transformer & a 10 watt resistor. I can get the resistor locally. But the transformer was a bit pricy. So I found a broken micro wave and stripped it down for the parts. My transformer has a solid core between the primary and the secondary that I did not have to take out before I stripped out the secondary and the shunt wires. Thank you for the instructions.
Thanks. you are awsome. I subscrube. you said it clear. one turn is 1 volt. google search said 60 turn for 12 V. so that ways too much. I almost make mistake, lucky I saw your video.
I am just a hobbyist. what are the shunts for? What is the added benefit of replacing them? I heard a engineer say you can leave them out for a 1 to 1 ratio "NOT SO SAFE" isolated Transformer. You will need the added room and the added coupling if doing that . Is there a benefit to putting them back in or leaving them out?
Hi Ronnie. The shunts provide an additional magnetic path for the core and limit the total flux passing through the secondary. While used in the microwave, this serves to limit the power going to the magnetron. If you're rewinding the transformer for another application, they can be removed. I recommend high temperature insulated wire for your secondary winding. If you're doing a small number of turns with very large cable, such as for a spot welder, I also recommend FR4 or mica spacers between the turns. MOTs can be very useful and fun but they are very powerful and can be dangerous. Always take extra care and respect them. Take care.
I might have missed it, but I think you must have wired the primary and secondary windings together? Is that a good assumption? So, you've got two ends sticking out of the primary and two ends of the secondary: do you wire the plug end (mains) to the TWO wires of the primary? But then...there aren't any wires to connect to secondary wire, or to go on to do any work--like spot welders and whatever else. I'm confused.
Good Day. Like your projects. Can you perhaps do a vid on Micro Oven Transformer for Home Generator. Many Thanks. Wayne. Alberton. Johannesburg. South Africa.
Great. I want to make my own isolation transformer (220220) and first I thought about winding my own, but 220 turns? it's gonna take me a while. Then I thought what happens if I take a couple of trash microwave transformers, take out the 220v primary of one and put it into the place where the seondary goes in the second transformer? I would get the same exact number of turns on both, so, 220-220v. So my lan is to use a metal ginder to cut the sheets and re-solder them, as I have seen in other videos. Doable?
You Really dont Need to Put the Magnetic shunts Back into the Transformer, Their purpose is to limit the current going into the Magnetron when its in the MicroWave cooker , When being used as an ordinary transformer you dont Need to limit the Max Current , this Type of transformer is a ferro resonant device running Near magnetic saturation , In the Microwave the Magnetron Runs at Max output in All Modes when at Half power its on for 30sec and off for 30seconds ................Ect anyway I enjoyed your video But Im an Electrician and I thought Might Profit from this Information cheers Bn
Got a couple of microwave transformers with the 240v winding primaries on. Got a couple of empty ones too, after I damaged the primaries. Building a circuit board with an output of 12v ac from H-Bridge Mosfets to produce a pure sine wave at 50 Hz. Each Mosfet is max 110 amps at 55 volts Max. I'll be gating them for 12 volts sinewave. I've also got 13 meters of enameled 3 mm transformer wire I'd like to use in the transformer. You say 1.04 volts per turn. It that in rms values or peak values. I thought I'd have to use 21 turns to get 12volts. I want to also wire in a centre tapped 12v ac output to gate slave mosfets to get between 3kw to 7kw output, depending on the transformer. This design is for a low frequency output using a H-bridge, I'd use the slave after it. But, I also.. want to use spare transformer primary winding to get to 400 volts plus, maybe up to nearly 600 volts. That is for the high frequency inverter output version. I've got the 600 volt, 47 A Mosfets for that. Be good to use that as a final output. I'd use a separate push pull circuit to generate an AC output, where I can control the voltage & frequency output, even change the wave form output using a filter circuit.. have a choice of square, trapezoidal, sawtooth or sine wave. Could then use the pulsed DC motor controller to drive an electric generator using frequency control. So, how many turns do I need for 12 volt RMS output? 11? or 12? I'd like to know how many turns to add on the primary side using the same enabled wire to boost it to 380 to 450 say. Thanks for the video, I learned more about transformers.
What about the magnetizing current? I checked the primary current of 4.5A from the 220V mains without having a secondary wound. The transformer heats considerably in a few minutes. I had to add ~80 turns to the primary to get ~ 400 mA AC. Victor Koren
A microwave oven transformer should never draw 4.5a with no load. Either the primary is shorting (unlikely without you know about it) I'd say running the transformer without a secondary is whats causing the high current draw.
I wound transformer small and large. I also tested some of them with only the primary winding without a secondary. The current was only a few milliamps. A microwave oven trafo is designed to work short term a few minutes at a time. The core is also undersized for the wattage it produces thus that is why they force them with magnetic flux making fewer turns to get more power out of them. That explain the extra off load current 3 to 4 amps.
+Schematix Without a secondary winding and also without any load on such secondary winding, what one has is a (resistive load) heater. Some would joke and say 'That's Cool"
These are designed to saturate in normal use, which is why they do, and get hot (also the reason for the shunts). Here in the states, with 120v nominal mains, this happens at 89 volts or so - same deal, you need more turns, or accept the waste and use a fan.
NO RUNNING A TRANSFORMER WITHOUT A SECONDARY WHAT ONE HAS IS AN INDUCTOR ( A BALLAST ) OR IF THE PRIMARY HAS ONE OR MORE TAPS A AUTO-TRANSFORMER ....... THESE TRANSFORMERS ARE NOT DESIGNED FOR CONTINUOUS DUTY ......
You will be surprised at how much current draw on the primary with no load on the secondary. It will be around 10 amps. If you kept it running for over 20 minutes or more, you couldn't touch it. You need to add some windings to the primary, ( around 30 turns ), because the amount of windings that it came with is wound for max load ( It's under wound for a reason ). That will also knock down the loud buz from the 60hz and the current draw with no load on the primary will be a lot lower ( around 1 amp ). This will not change the secondary output, it just won't catch on fire. I would rather draw 1 amp with no load than 10 amps with no load, and keep my house from burning down.
i have a similar setup for 9v dc using a bridge rectifier. and i cant work out why. when i change the brown and blue AC inputs 240v leads over, i get 4.5v dc output i was expecting there would be no change. any ideas?
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.
Throw those shunts away! They reduce the efficiency of the transformer by storing magnetic flux instead of letting it pass through the secondary winding to the core material on the "other side" of the secondary. By distorting the sine wave passing through the secondary, they also add a hideous amount of harmonic distortion to the output. Those shunts are how they turn a 1500 Watt device into a 1000 watt device.
I did a rewind of one of these and tossed the shunt strips. I was wondering whether I made a mistake when I saw this. Can someone explain exactly what they are there for?
@@phbrinsden: Here's the thing - iron and steel can hold a lot more magnetic field than air.can. So in an un-shunted transformer, when the magnetic field starts increasing around the primary wires it can swiftly move through the air, cut through the secondary windings, and then get stored in the steel core where it moves much more slowly due to the steel being able to hold a much denser magnetic field. You are giving the magnetic field someplace to go after it has crossed the secondary windings. But if the magnetic field has to go through a shunt before it passes through the secondaries, the shunt is going to store the field until it saturates, and only then will it start releasing the stored field into the air on the secondary side of the shunt to then pass through the secondary windings and then it will be stored in the core steel. But some of the magnetic field generated by the primaries is always going to be stored in that shunt and never reach the secondary windings. They can very effectively tune the power output of the transformer this way. It also lowers the voltage on the secondary side of the transformer, as well as introducing several harmonics of the original 60 hertz input wave.
Great Work, patience in explaining and teaching style 👍🏽 With the wire melting, you could just go in for a heat resistance insulation cable or wire for that "MICA FIBER COATED CABLE".
Not very energy friendly. For 120v MOT it read 4.4 Amp on the primary with nothing connected to the secondary. That about 500w of power just being plugged into the mains. Very disappointing. I get 25v on the secondary; about 25 turns of AWG 16 wire.
Could I use an extension cord for the secondary winding. I have lots of this wire but it has the neutral, hot wire, and ground wire in it. If I just twist these together will it still work fine?
Nice tutorial :) I happen to have an old microwave oven in my basement, I'm going to give a new life using your video as a guide, thank you very much :)
@@Schematix gov will have all heads for this tech thay teach us that we always have loss but never talk about the converted gain we can make from eletromagnets if u convert all the wast thermal energy around you u can use it universally as energy u need a true sine wave bipolar like the power comp dose a true pure sinewave like a grid tie inverter once the signal is made the system will turn on and consume wast thermal energy from the environment and space around you... there is free energy but it comes from Universal thermal loss and converted into a gain. so a pole Transformer and a microwave Transformer have a common between each other u can take 2 microwave Transformer provide a pure sine wave grid tie inverter to it or a true bipolar sinewave that inter acts with nature in a perfect spherical motion like a flower of life.. if ur home provides this use it as a Source signal then u can simply stack the Transformers on top of eachother in correct fasion and note that the 1 wire on the Transformer must stay connected and the other disconnected your only useing 1 wire on the hi side .. so test ur self 2 microwave transformer stacked on top of eachother same face sides. one side 120 to the wall and the other 120 side to what u want to power and useing the Transformer just the way it came out the microwave with the wire attached causes the energy in its perfect spherical motion to converted wast thermal energy to amp for u hot to cold in to out... should look a bit nuts with u use a form of wireless energy but its interacting with the environment...this is my work a compilation of Otis car. Tesla. and many other very smart people nowadays i think i found the gate source and drainif this gets out to much that it works the power comp and mib will have our headsdont do this at home warning high voltage yet i cant stop u lol DO NOT TOCH THE CORES OR THE WIRES OK u will die make sure u dont touch the core if the hi wire is mounted to it u dont have to mount the hi on the core if u dont want u connect the 1 hi wire to the same side hi on the other transformer then the core should besafe to handle if nessary
@@Schematix gov will have all heads for this tech thay teach us that we always have loss but never talk about the converted gain we can make from eletromagnets if u convert all the wast thermal energy around you u can use it universally as energy u need a true sine wave bipolar like the power comp dose a true pure sinewave like a grid tie inverter once the signal is made the system will turn on and consume wast thermal energy from the environment and space around you... there is free energy but it comes from Universal thermal loss and converted into a gain. so a pole Transformer and a microwave Transformer have a common between each other u can take 2 microwave Transformer provide a pure sine wave grid tie inverter to it or a true bipolar sinewave that inter acts with nature in a perfect spherical motion like a flower of life.. if ur home provides this use it as a Source signal then u can simply stack the Transformers on top of eachother in correct fasion and note that the 1 wire on the Transformer must stay connected and the other disconnected your only useing 1 wire on the hi side .. so test ur self 2 microwave transformer stacked on top of eachother same face sides. one side 120 to the wall and the other 120 side to what u want to power and useing the Transformer just the way it came out the microwave with the wire attached causes the energy in its perfect spherical motion to converted wast thermal energy to amp for u hot to cold in to out... should look a bit nuts with u use a form of wireless energy but its interacting with the environment...this is my work a compilation of Otis car. Tesla. and many other very smart people nowadays i think i found the gate source and drainif this gets out to much that it works the power comp and mib will have our headsdont do this at home warning high voltage yet i cant stop u lol DO NOT TOCH THE CORES OR THE WIRES OK u will die make sure u dont touch the core if the hi wire is mounted to it u dont have to mount the hi on the core if u dont want u connect the 1 hi wire to the same side hi on the other transformer then the core should besafe to handle if nessary
Excellent explanation of how to get the voltage required from the mains but what about getting an exact amount of current? Or is that way more complicated.
bro what is the size of thhn wire you used for the secondary rewinding?? and i want also to know how much the a.c input of the primary in order for you to rewind the secondary winding..? thank!
very helpful I am an electrician and have 3 microwave Transformers. And was thinking of making a welder. Using number eight stranded silicone coated wire. Any thoughts ? someone told me the wire you wrap around The secondary should be in the same direction as the primary.
You can't make an Arc welder using a microwave transformer, it won't handle it. You can make a battery nickel strip spot welder using 2, 3 or 4 turns of cable plus a timer trigger module designed for the purpose. . You need bigger than AWG 8 to get decent reliable welds. You might to it with 2 Or 3 parallel connected AWG 8, which will be cheaper and easier to wind than single AWG 4. Check the AWG cross sectional area specs chart. . You will struggle to get a MOT to do sport welds in steel. The main use is for nickel strips under 1.5 mm thick. . The direction of windings only matters if you are connecting more than one transformer in Series or Parallel. If they are out of phase, you got it wrong, so reverse connections on one transformer (You can reverse the primary if you like).
OK, nice enough tutorial. Question: Did you need 21 working volts? If so, throw on a couple more turns, as the voltage will drop when you add the load. Also: Folks, please, if you're going to be teaching other people how to do things, at least use the proper tools. Screwdrivers are not drift punches or pry bars. Please show the people the proper tools to use for the job so they don't pick up bad habits from the start.
@@criticallook1352 He used a screwdriver to pry. (I said they're not pry bars) He used a screwdriver to drive parts. (I said they're not drift punches) Now, if you can't figure out what the proper tools are, you have no business watching these videos. DIY is not for you. ;)
I saw microwave up the street I think I might go ahead and yank it. I got a few Transformers around the house I think I might actually try winding one of them my battery charger just quit and it was taking a lot of current and I found that the windings for the secondary or absolutely crispy so I guess I might try to go to wine that really quick just for fun
Why manufacturers not using insulated wire like u did to wind transformers...this will prevent short circuit of transformer...i guess they don't want to run out of business
Yeah us Kiwis are not too keen on vowels, so we decided to only use one. This is how you can tell us apart from the Aussies. They like vowels so much, that when they get to one they just hold onto it for as long as possible. Geeedaaaay Maaaaate.🤠
great tutorial! Saved me some troubles and just gonna re purpose my surplus of microwave transformers haha. Wish they made it so you could salvage and re purpose all of it. Having to cut it apart it kinda bad design tho I know why they claim to do it that way. =/ Oh also, my only critique for safety purposes would be when conducting the test to make sure the transformer isn't grounded, make sure to test that the place your grounding from is in fact a good ground contact point by touching lead to where you would like to have ground point and another random spot on the former with another. This leaves no room for error really. Or at least reduces it severly as I know I've had times where I thought I was on good grounds but was in fact weren't and double checking like that really saved me! Thanks again bud!~
This is not practical at all. This transformer gets Extremly hot under normal load. Because the input power is too much. I tried many time in the past to build high current power supply out of it, but no hope. Only you can built Spot welder.
The shunts do limit the power to a limited degree. However, without them, most transformers will run much hotter and consume much more power even while idle. I don't really recommend removing them entirely. :)
I’m very late to this party. I hope you might find a moment to answer a question. If you have rubbed the insulation off more than just one of the turns on the primary winding, is there any thing special you have to do to ensure they don’t touch under the lacquer insulation? On rewatching I have a couple more questions: 1. Is there any advantage to making the wooden blocks more of an arc shape so the secondary coil turns are more circular as they pass outside the core from one side to the next? 2. Is the purpose of the shunts to add a ferric (“magnetizable”) spacing between the coils? Or are they there to reduce the air-gap between the coils, getting as much magnetizable material as possible between the coils?
the purpose of the shunt , it change the behaviour of the transformer from a voltage source to a not so good current source , it is needed because the magnetron act as a zener diode , if the shunt were not there hi line voltage ( input voltage ) would destruct the magnetron .
There is a formula 4 the number of windings the primary and secondary. If you only change the number of turns on the secondary then the Transformer is no longer at Max efficiency. Am I correct? Another important detail I wish you'd covered was Magnet Wire versus insulated wire. I still learned a lot from the video. I really enjoyed it. Thank you.
He probably learned these transformers make for bad power supplies, you can't run them for very long before they overheat. As others have commented you need to add more primary windings.
Not a bad tutorial........for a Kiwi. Seriously though this is just what I was looking for as I have collected plenty of microwave transformers and I am looking to make an electromagnetic chuck/ machining plate. I had it pretty well sorted except for a power supply. I was looking for something around 40 - 50 volts dc but they are thin on the ground and as you said expensive but now you have shown me the way. I figure if I build a transformer like you have shown and configure it to put out about 35 volt Ac and then pass it through a bridge rectifier I should end up with around 42 v dc. Dc giving a stronger magnetic field. Thanks again mate. Cheers Stuart 🇦🇺
how you get 42dc from 35ac ?! and i advise you to take many line from secondary so you get many ac volt sorry about my stupid english and did you know what wire gage or size he use for 15 amp ?
@@scroungasworkshop4663 Thinks for the idea I will try it and tell you soon I think diodes reduce voltage but maybe there's something i miss Stay safe and take care my friend
@@scroungasworkshop4663 AC voltages are usually given as RMS while the peak is ~50% higher, eg 240v has a peak of 325v. Your bridge rectifier converts peak AC to DC, so it comes out higher. The bridge has 2 diodes and will drop about 0.6v each. RMS is the DC equivalent of peak AC, so a resistor at 325v AC (peak) will put out the same amount of heat as one connected to 240v DC..
In my country you have to recycle all electronics, its forbidden to dispose a microwave with household waste. Even at the local recycling center they do not allow you to take an old microwaves with you. My only source for transformers is eBay. Good for the environment, bad and expensive for DIY :-(
+Lejf Diecks You may find used microwave ovens in stores that sell used equipment, Also ask in stores that sell new appliances, they always have access to 2nd and 3rd Quality appliances from distributors. Also ask in any TV repair workshop. Another option is to place an advertisement in the local newspaper, stating that you collect used microwave ovens, and you will have more transformers than you will know what to do with and a lot more useful parts ---
Hello my friend. Your video is very detailed and I watched it with great interest. Long ago I saw a video of you in which you used this transformer to make a laboratory power supply. I'm trying to find this video, but I can not find it. Can you send me the link?
I would like to build a 12/24 Volt charger/ jump start for my tractors. Would you be interested in showing how this could be done? Thanks, Randy. We are at -49* below up in Canada right now and always in need of such boosters during winter. They want over a thousand dollars for one. I even have quick connect heat lines between motors but when the batteries are down you’re done.
Thanks, awesome vid. Q With the secondary, you did a test of 10 wraps. Did you join those first 10 wraps to make your end result of 20+ wraps? If so how would you do it. Cheers Glad I found your site.
Thanks for the feedback. There is no joins in my secondary. It's a continuous length of wire. I tested with 10 turns and left the remaining wire on the spool I was feeding from. That way I didn't have to cut the wire :)
What gauge wire did you use for the secondary winding? I'm in the U.S., which is likely a different standard, but I can figure out the conversion. Thank you!
if you draw 15 amp it will melt thanks to the tick insulation on the secondary get some real transformer wire, look for company's who are rewinding electric motors.
I've just stripped our old microwave. I'll sell the magnatron on ebay and re-wind the transformer to give an output of around 7V reg/rec down to 5VDC to power the auxiliary circuit on my model railway.
Just a word of warning. Be very careful when dismantling a microwave oven. There is there is a massive capacitor, which can hold a lot of current. If its still holding its current it can kill you. Be Especially careful with older models, newer models should have a bleeder to slowly bleed off the current. Just be careful and watch out for this capacitor and you should be ok. P.S. It is best to wait until the missus has finished cooking her 2 minute noodles. Ooh and don't forget to unplug it before dismantling.🤪
Build a Rather Hefty Battery Charger doing this. Was able to start my truck engine using the thing. Did just fine cranking the engine for a few seconds at a time. Any more then that and it would have melted down I'm sure but it worked.
I will try this but I'm going straight to cutting the secondary coil with the hacksaw. I'm skipping the step of removing the shunts before removing the secondary. I'm hoping the shunts are easier to remove after removing the secondary. [Oh!] Now I see the secondary is glued in place as you said and the shunts prevent levering it out. Okay. Nice work. Thank you.
Really good information, nicely presented. I have one constructive comment: You need to open your mouth more when speaking. You are quietly spoken (as am I), and therefore we need to open our mouths a little bit more when speaking so it's clearer. It could be nerves too - was that your first video? Anyway, good job overall.
hi thanks for this....advice= use an angle grinder, (i use homemade steel chopsaw 14 inch)to cutoff secondary.Shunts are needed in the redone core, as well, to separate magnetism. Also, a ground down railroad spike works best, to hammer out secondary core...fits like a glove. I've done many of them.......alternatively, also grinding off the welds, and take-apart the core.....works as well....then, weld up when done winding secondary bobbin.....
no way jose on that pricing,not sure where u would get ripped off for 100 to 200 for just one transformer when u can once again go on amazon or find used ones complete for $50. used ones for hamradio etc can go from 50 to 150 and 20 amps complete ie Pyramid or astron supplies,but dont misunderstand me,this is all good hobby work
Hey man!! Awesome video. I'll be doing this to power an electrolysis chamber to launch marbles in my "marble machine".....very informative, thanks!! I see lots of interesting videos on your site, and I just subscribed!!
Hello teacher, yes this old man has understood you more then others, im hopeing please youd help me a bit, Thank You . Im wanting to make a 25 amp battery charger and ive watched a few vidieos on the channal and not getting all i need to know or understand, showing my lack of electrical knowledge i first missed you ground to the outside of the transformer, does it also connect to the other terminal or the primary winding ? into the power supply 220 ? earth ground im told here in the philippines. Make a Long story short on you , Would Be beautiful to see a vidieo of you builing one, i dont know what size rectifier or other components / n rateings needed. If you find time please be my guide. Thanks Really and thanks for the smile with your humor with infected /effected :-)
Most transformers will be warm without any load. In simple terms you have to remember the primary winding is effectively a wire wound resistor between live and neutral and will always use some limited amount of energy even while no load is being drawn on the secondary. How hot the transformer gets does depend on a number of factors. I've got a couple commercially made transformer that easily break into the 50 degrees celsius mark. However If your transformer is too hot to touch there maybe a problem
nice video I tried to make a spot welder. For it i bought a used MOT, the seller connected ac voltage to the primary winding (thin wire side). And it created humming sound. At home I removed that side and when I connected ac to the secondary side it created smoke and smell and became very hot to touch. Seems like the Secondary was already short? What you say? Also Now can i rewind it using suitable size enameled wire? Will winding it with slightly thinner wire be ok for spot welding? Current winding is using 0.9mm enameled copper wire and the length and breadth of cross sectional area is 15 by 17 mm..
OH MY GOD!!!!! WOW!!! HE SPEAKS!!! THANK YOU!! THANK YOU, THANK YOU, THANK YOU, for not just playing shit music, or typing words on the screen during editing!!!
By far. The ONLY REAL Rewinding Transformers Video IVE SEEN!!!!
WOW!!! GREAT JOB, JUST BECAUSE YOU SPEAK!!!!
And I bet I know why you speak. Because you actually know what you're doing and why it works. Not just "HOW" to do it, like most of the hacks out there making videos with music and text that just tell you DO THIS!!! And don't explain a thing.
YOU KNOW WHAT YOURE DOING@@@ YAY!!!!
BEST VIDEO!!!
Excellent video. Well explained, well demonstrated, well presented. And no irritating background music, for which you earn my eternal gratitude.
Fully agree, no music needed
Just drive the shunts a bit not all the way. That way they protect the primary from the hacksaw.
These transformers are no good for this purpose, they are not designed to run continuously and they are overdriven to keep cost and size down, a transformer designed for 800 - 1000w continuous duty cycle would need o be twice this size.. Driving the transformer in this way means it has a very high idle current of usually over an amp or even more but even at 1A 240v thats 240w being dissipated needles to say they get HOT fast even with no load...
It appears this is mostly a mechanical how-to. Maybe it helps if I add some electrical comments. First, there are some manufacturer data sheets for transformer sizing. Generally the more power required, the heavier the core becomes, KEEPING the line frequency the same. A higher frequency allows reduced weight, up to a limit. Above some 400 Hz, you need better (thinner laminations and those insulated from each other, also no more welds) materials and above 20 kHz you likely need to switch over to ferrites.
Then, the optimum tradeoff between core and winding heat losses comes at near 1:1 ratio of the iron cross area and the window (core space) cross area. The winding formula is n = U/(4.44 f b A), where n is number of turns, U is the applied RMS voltage, f is the frequency, b is the allowed peak magnetic field and A is the iron cross section. All these in the metric system, i.e., the A is in square meters and b is in teslas. The b depends on the iron quality and varies from 1.2 to 1.3 for most practical materials and some 1.55 to 1.7 for some crystal oriented materials.
Then, about the shunts - they are actually causing leakage magnetic field ("radiation"). Their purpose in the microwave oven is to LIMIT the current. As such, they also cause additional heating of the transformer. Along with too few turns in the primary, they are a cause of higher primary current (which was a concern in another comment). For a bench power supply, where you should do current limit in electronics, you should replace those shunts with some wood or plastic strips. That would improve your efficiency, although it would increase your INRUSH current, as the limiting action is discarded.
I hope this info still reaches some people who might benefit from it.
Would it be any better if we used a piece of plastic and one metal shunt then another piece of plastic, I'm new at this, thanks
Great info!
Pellervo Kaskinen thanks for the info , for anything related to laminate I use the 42 constant, which is the Ae area effective divided by 42
I.e 42/ Ae = Tpv
Tpv = turns per volt
I have tested this extensively and can not fault it including ‘blind’ tests where I used it to predict the turns then unwind various ‘consumer’ windings to find it accurate, even on large turn numbers, however this equivalent may help with trying to derive a new ‘constant’ for various crystal hybrids so thank you .
I don’t have my book here immediately but yes the primary of a microwave Transformer has missing meters worth of inductor based both on the 42 constant and on me predicting then unwinding. I believe it was missing many meters. This and other factors contribute to the excessive heat and energy loss that these lovable and famous devices radiate. Regards.
Pellervo Kaskinen I think I understand about 50 % of that.
I have a question for you since you seem electrically inclined. I'm looking to rewind one of these transformers for an even higher voltage by grinding off the weld and pulling the "E" "I" sections apart to access the core. I'm wanting to build a secondary out of 32 AWG wire with about 32000 turns to get roughly 30000v at 30mA. Will this turn count be sufficient?
Assume I take the necessary precautions such as yellow tape bettween layers, in addition it will be submerged in mineral oil. Supply power will be fed to a variac and the output of the variac to a bridge rectifier (no capacitors) with a 15amp fuse that feeds the primary winding which will be kept untouched.
Will such a setup work?
I used to rewind small transformers when I was teenager back to 30 plus years ago. This video just let me recall all the steps I encountered like cutting punching measursing guessing patching...
I very much enjoyed the work I did. Thank you very much and great work you have acomplished.
go learn what is ,gauss, maxwell ,core properties, winding ration,core size,constant numbers, a lot of formulas, hz, and so then play w/transformers ,MOT THEY ARE JUNK ,JUNK,JUNK,if you hookup a oscilloscope on the secondary side after you rewind this thing tel me what kind of sin wave you see on the oscilloscope ,HO GOD you do not want to see another MOT again ,I work for transformer companies 40 years wind this things ,i love them when they are design the right way
less time - you should spend MORE TIME learning how to read and write.
less time. What is being demonstrated here is what can be done “on the cheap”. Ok, you’re not going to run your laptop off it but it would be fine for running an electric motor and other things that don’t need a clean supply. I am making one to put out around 48 volts DC to power 3 other MOT’s that will be turned into an electromagnetic chuck. Where does the average bloke like me get the parts to build a “proper” transformer and how much would that cost. You say they are junk BUT there are a lot of tutorials on RUclips showing lots of successful projects being made from them. To be honest you came across as a bit of a smart arse in your reply. We are not building professional transformers here we are using almost free parts to make something useful. It’s called a hobby. I have worked with automotive suspension but when someone builds a billy cart I don’t tell them to go learn about steering geometry, toe in, caster angles, camber angles first and then play with steering and that the crappy little wheels they are using are JUNK, JUNK, JUNK. It’s just a hobby mate. Who cares as long as it works and no body gets hurt.
An oscilloscope? You have got to be fucking joking. Most blokes are just building stuff with these things in their shed.
I see it fairly regularly on videos where the “PRO’s” chime in, get all technical and confuse the shit out of the average bloke trying to learn or make something. You have added nothing positive to the subject. All you have done is succeeded in big noting yourself as an expert and putting everyone else down. We all know MOT’s are junk, that’s why they get thrown away. Why don’t you post a video and show us all how we can make a proper transformer in our own garage for next to nothing. Now that would be helpful.
You need to remove those shunts & NOT HAVE THEM IN THE FINAL TRANSFORMER. (If you want mechanical support, put in wood sticks instead.) If you leave them in, the transformer's output will be "wimpy" & collapse when load is put on.
And also I don't understand why the secondary was wound with a large gap to the core.
@@paulcohen1555 The "gap" is filled with iron laminations, just like the rest of the frame. This provides a "short circuit" path for the flux. In "ordinary" transformer, you want ALL the magnetic flux to loop through BOTH the primary & the secondary windings. Any flux that "short-circuits" & does not link both causes "leakage inductance". This inductance causes the output voltage to sag when the transformer is loaded. But "microwave oven transformer" is NOT a PURE transformer. The leakage inductance resonates with the capacitor that is series-connected, & these are connected to the tube. This causes the output voltage to rise much higher then the turns-ratio calculations would indicate. The voltage rises until those magnetic shunts saturate, limiting & regulating the current feed to the microwave tube. (Microwave tube "doesn't know when to quit". It will draw current until it blows up if it were not for this limiting mechanism!)
When making "ordinary transformer" from microwave transformer, both the capacitor & the magnetic shunts should be removed, as this regulation is not wanted.
Video should be titled: "How to rewind a microwave transformer into a step down transformer power supply."
@Michael Reynolds..... upcomming DIY video.........How to rewire a Video Title ....!!! Lol !
MOTs are made as cheaply as possible and are NOT meant for continuous service...the idle current is way too high due to the absolute minimum number of windings in the primary, you need to add 10 to 20 turns in series with the primary for continuous service which will reduce the idle current a lot. Also it is way easier to use an angle grinder to grind off the welds holding the "I" and "E" sections together and then push the primary off in one piece, you can then reuse this wire for something else...MOTs are great for making DIY transformers, light dimming chokes (even variable with adjustable "I" section gap, I have even made audio output and speaker impedance matching autotransformers with them...
Great vid bro. Thanks. Just a add on, for those who need a 2xVAC with center tap, just double the wire turns and pull a tap at half the turns. Of course wire diameter will limit the possible number of turn. One can use enamelled wire instead of PVC insulated to lower the overall wire area necessary.
With the size wire you are using for the secondary, I would watch for excessive heating, even at 10 amps. Remember, the normal current rating for hookup wire is in free space where it is cooled. When you put it in a tight coil, it can't cool as easily. Use larger wire with thinner, higher temperature insulation, less heat. Play it safe.
That is definitely the wrong type of wire,enameled wire is best,not worth taking short cuts.Very dangerous stuff your playing with.Transformers heat up a bit so you have to think about the long term usage.Think safety always. Good luck!!
Hi, what happened to the follow-up video with the charger? I had it bookmarked but it's MIA
I just wanted a bright flashlight...
I learned about flashlights,
which led me to batteries, which led me to power packs, which led me to
battery balancing, which led me to variable power supplies, which led
me to "make your own PS", which led me to transformers... here I am
learning about how to make your own transformer... where am I going from
here? How to harness the power of the sun to power your power supply? I
feel like I'm a in a free fall...
I just wanted a bright flashlight...
I just wanted a new external battery for my phone...
You talk too much. . . . . .
Taunter Atwill somebody has to tell them!
We seem to have had very similar paths! I'm now working with solar, supercapacitors, and solid state batteries. It's an addiction.
And that's how I'm into electronics.
If you paid 10 dollar for that small amount of wire, you got ripped mate!
How do you rewire the primary windings
This video is boring and aimless which is bad. But it's also totally wrong from a physics perspective, which is unforgivable. You clearly have no idea what the shunts are there for, so you put them back: possibly the daftest thing you could do.
Bruce Clothier
Maybe it's time for you to grow a brain?
Can I use radio transformer in state?
So what will you do with the 21 volts
After removing the secondary coil I tested the primary using 240V. After 30 mins. the temperature had risen to just under 100C. That's no load whatsoever. The primary uses around 70Watts no load, this may not sound much but it's all going into that small primary. The only real answer is to add more turns to the primary but that's messing about with mains Volts, unless you really know what you are doing make sure your will is up to date. It did seem to stabilise at around 100C but what happens when the secondary is used for half an hour I have not yet tested. 'China Syndrome' ? - 'Frying Tonight' ?
This is a bit late, hopefully you are still monitoring comments: is there a non-destructive way to determine the number of turns on the primary in order to match the secondary to it? I want to wind a 1:1 transformer to use in my shop for isolation. I would use good quality magnet wire of the same size - shouldn't you use proper insulation rather than masking tape? I've seen Nomex paper insulation used before. Wonder where to get that?
Nice tutorial.
This reply is even later 😅 ...
The easiest way is to locate two *_identical_* MOTs, and use an angle grinder to cut the 2 welds that hold the top onto the H lamination. Drive the secondary windings out then hammer the primary out of one transformer using wood blocks. Refit both primary windings into one core, then weld the lid back on.
....
Things to note:
1. Modern MOTs use aluminium for the primary windings, which needs to be thicker than copper for a given power level.
.
2. Microwave transformers are NOT designed for continuous use and have huge power losses (even with no load). This is because of too little steel in the core. So they really are not good for use in proper long term operation.
.
3. The secondary of a 1:1 isolated transformer may need more windings that the primary. This is to correct two sets of voltage sag under load.
.
4. Almost all MOTs have a primary with the same number of turns as the rated mains line voltage. So a 110V transformer will have 110 turns, a 230V transformer will be the same sized core with 230 turns of thinner wire, etc.
.
5. To accurately work out the quantity of turns, wind a test then do math. Start with (say) 20 turns, measure AC Voltage, then divide by 20 to get the resultant "volts per turn". Then finally, wind your calculated quantity on but leave it long until you test voltage again and add/remove as needed to hit your target voltage.
.
6. Use an accurate True RMS multimeter. Cheap ones (especiall if not true RMS) will give you strange readings that will skew your calculations.
Why destroy a winding you could use in another project?? Grind the welding off and dismantle the transformer.
I just uploaded a video to my channel of how a microwave transformer is correctly modified
Great video.
Just a note though. The wire can manage 15 Amps, but not when it wound in a coil. The 15 Amps are for normal installation.
Zeedijk Mike
Peak values.
Just a few hour ago, I got rid of the secondary winding painfully. Then I removed the shunts because they helped protect the primary winding while drilling and hammering the secondary winding. By the way the windings are Aluminum, so be very careful not to damage the primary as its not easy to repair or solder. The outer surface of the primary winding got a bit of a scratch, it's dangerous it touching while connected to power. So I covered it with lacquer.
Well, i think that was very interesting, didn't know it was that easy to do.....keep making vids like these please
I question that.i did this on two different transformers.with same # of turns as you.transformer got smokin hot from the constant 4 to 5a load on primary.dont buy it at all,show me the line current on pri. With no load secondary...perhaps you cut the welds on the iron and changed laminations.these transformers are saturated on core.
I just finished cutting the secondary winding out of a transformer. I am following your directions for the winding. I want to make a 24 volt- 10 amp unit to power a CNC machine. I have all the parts except a transformer & a 10 watt resistor. I can get the resistor locally. But the transformer was a bit pricy. So I found a broken micro wave and stripped it down for the parts. My transformer has a solid core between the primary and the secondary that I did not have to take out before I stripped out the secondary and the shunt wires. Thank you for the instructions.
Thanks :)
@Schematix pls leave an email address I can email you via?
ARCSTREAMS
Amp meter?
Thanks. you are awsome. I subscrube. you said it clear. one turn is 1 volt. google search said 60 turn for 12 V. so that ways too much. I almost make mistake, lucky I saw your video.
I am just a hobbyist.
what are the shunts for?
What is the added benefit of replacing them?
I heard a engineer say you can leave them out for a 1 to 1 ratio "NOT SO SAFE" isolated Transformer. You will need the added room and the added coupling if doing that .
Is there a benefit to putting them back in or leaving them out?
Hi Ronnie. The shunts provide an additional magnetic path for the core and limit the total flux passing through the secondary. While used in the microwave, this serves to limit the power going to the magnetron. If you're rewinding the transformer for another application, they can be removed. I recommend high temperature insulated wire for your secondary winding. If you're doing a small number of turns with very large cable, such as for a spot welder, I also recommend FR4 or mica spacers between the turns. MOTs can be very useful and fun but they are very powerful and can be dangerous. Always take extra care and respect them. Take care.
so, you rewind the transformer...but can you fast forward the transformer?
Unfortunately, it can not put you on pause, let alone, shut you down. :)
Can you use 2 12v Transformers. Connect the secondary, and create an isolation transformer?
I might have missed it, but I think you must have wired the primary and secondary windings together? Is that a good assumption? So, you've got two ends sticking out of the primary and two ends of the secondary: do you wire the plug end (mains) to the TWO wires of the primary? But then...there aren't any wires to connect to secondary wire, or to go on to do any work--like spot welders and whatever else. I'm confused.
Good Day. Like your projects. Can you perhaps do a vid on Micro Oven Transformer for Home Generator. Many Thanks. Wayne. Alberton. Johannesburg. South Africa.
GOOD LECTURE, HE KNOWS HOW TO EXPLAIN TO PEOPLE WHO ARE STILL LEARNING, GREAT JOB BOSS
Great. I want to make my own isolation transformer (220220) and first I thought about winding my own, but 220 turns? it's gonna take me a while. Then I thought what happens if I take a couple of trash microwave transformers, take out the 220v primary of one and put it into the place where the seondary goes in the second transformer? I would get the same exact number of turns on both, so, 220-220v. So my lan is to use a metal ginder to cut the sheets and re-solder them, as I have seen in other videos. Doable?
You Really dont Need to Put the Magnetic shunts Back into the Transformer, Their purpose is to limit the current going into the Magnetron when its in the MicroWave cooker , When being used as an ordinary transformer you dont Need to limit the Max Current , this Type of transformer is a ferro resonant device running Near magnetic saturation , In the Microwave the Magnetron Runs at Max output in All Modes when at Half power its on for 30sec and off for 30seconds ................Ect anyway I enjoyed your video But Im an Electrician and I thought Might Profit from this Information cheers Bn
Got a couple of microwave transformers with the 240v winding primaries on. Got a couple of empty ones too, after I damaged the primaries. Building a circuit board with an output of 12v ac from H-Bridge Mosfets to produce a pure sine wave at 50 Hz. Each Mosfet is max 110 amps at 55 volts Max. I'll be gating them for 12 volts sinewave. I've also got 13 meters of enameled 3 mm transformer wire I'd like to use in the transformer. You say 1.04 volts per turn. It that in rms values or peak values. I thought I'd have to use 21 turns to get 12volts. I want to also wire in a centre tapped 12v ac output to gate slave mosfets to get between 3kw to 7kw output, depending on the transformer. This design is for a low frequency output using a H-bridge, I'd use the slave after it. But, I also.. want to use spare transformer primary winding to get to 400 volts plus, maybe up to nearly 600 volts. That is for the high frequency inverter output version. I've got the 600 volt, 47 A Mosfets for that. Be good to use that as a final output. I'd use a separate push pull circuit to generate an AC output, where I can control the voltage & frequency output, even change the wave form output using a filter circuit.. have a choice of square, trapezoidal, sawtooth or sine wave. Could then use the pulsed DC motor controller to drive an electric generator using frequency control. So, how many turns do I need for 12 volt RMS output? 11? or 12? I'd like to know how many turns to add on the primary side using the same enabled wire to boost it to 380 to 450 say. Thanks for the video, I learned more about transformers.
What about the magnetizing current? I checked the primary current of 4.5A from the 220V mains without having a secondary wound. The transformer heats considerably in a few minutes. I had to add ~80 turns to the primary to get ~ 400 mA AC.
Victor Koren
A microwave oven transformer should never draw 4.5a with no load. Either the primary is shorting (unlikely without you know about it) I'd say running the transformer without a secondary is whats causing the high current draw.
I wound transformer small and large. I also tested some of them with only the primary winding without a secondary. The current was only a few milliamps. A microwave oven trafo is designed to work short term a few minutes at a time. The core is also undersized for the wattage it produces thus that is why they force them with magnetic flux making fewer turns to get more power out of them. That explain the extra off load current 3 to 4 amps.
+Schematix
Without a secondary winding and also without any load on such secondary winding, what one has is a (resistive load) heater.
Some would joke and say 'That's Cool"
These are designed to saturate in normal use, which is why they do, and get hot (also the reason for the shunts). Here in the states, with 120v nominal mains, this happens at 89 volts or so - same deal, you need more turns, or accept the waste and use a fan.
NO RUNNING A TRANSFORMER WITHOUT A SECONDARY WHAT ONE HAS IS AN INDUCTOR ( A BALLAST ) OR IF THE PRIMARY HAS ONE OR MORE TAPS A AUTO-TRANSFORMER ....... THESE TRANSFORMERS ARE NOT DESIGNED FOR CONTINUOUS DUTY ......
You will be surprised at how much current draw on the primary with no load on the secondary. It will be around 10 amps. If you kept it running for over 20 minutes or more, you couldn't touch it. You need to add some windings to the primary, ( around 30 turns ), because the amount of windings that it came with is wound for max load ( It's under wound for a reason ). That will also knock down the loud buz from the 60hz and the current draw with no load on the primary will be a lot lower ( around 1 amp ). This will not change the secondary output, it just won't catch on fire. I would rather draw 1 amp with no load than 10 amps with no load, and keep my house from burning down.
i have a similar setup for 9v dc using a bridge rectifier. and i cant work out why. when i change the brown and blue AC inputs 240v leads over, i get 4.5v dc output
i was expecting there would be no change. any ideas?
OL means open line not over load!
Actually it means "open loop" but close enough..
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.
What would I need to do for 85 volt secondary with a max draw of 135 amps? How would I keep it from overheating? Bigger core with thicker wire?
Throw those shunts away! They reduce the efficiency of the transformer by storing magnetic flux instead of letting it pass through the secondary winding to the core material on the "other side" of the secondary. By distorting the sine wave passing through the secondary, they also add a hideous amount of harmonic distortion to the output. Those shunts are how they turn a 1500 Watt device into a 1000 watt device.
I did a rewind of one of these and tossed the shunt strips. I was wondering whether I made a mistake when I saw this. Can someone explain exactly what they are there for?
@@phbrinsden: Here's the thing - iron and steel can hold a lot more magnetic field than air.can. So in an un-shunted transformer, when the magnetic field starts increasing around the primary wires it can swiftly move through the air, cut through the secondary windings, and then get stored in the steel core where it moves much more slowly due to the steel being able to hold a much denser magnetic field. You are giving the magnetic field someplace to go after it has crossed the secondary windings. But if the magnetic field has to go through a shunt before it passes through the secondaries, the shunt is going to store the field until it saturates, and only then will it start releasing the stored field into the air on the secondary side of the shunt to then pass through the secondary windings and then it will be stored in the core steel. But some of the magnetic field generated by the primaries is always going to be stored in that shunt and never reach the secondary windings. They can very effectively tune the power output of the transformer this way. It also lowers the voltage on the secondary side of the transformer, as well as introducing several harmonics of the original 60 hertz input wave.
Bogy Wan Kenobi Awesome, thanks for explanation.
Why did you put the shunts back in? I've seen people remove them before, and typiically they just left them out...
I wish I`d see your off camera AMP TEST of this hand-made transformer/ it looks great /Thank you man
Great Work, patience in explaining and teaching style 👍🏽
With the wire melting, you could just go in for a heat resistance insulation cable or wire for that "MICA FIBER COATED CABLE".
BE VERY CAREFUL with These Microwave TransFormers! I saw my FireFighting Sister son Cook himself with one of these bad boys.
Not very energy friendly. For 120v MOT it read 4.4 Amp on the primary with nothing connected to the secondary. That about 500w of power just being plugged into the mains. Very disappointing. I get 25v on the secondary; about 25 turns of AWG 16 wire.
Natural Suntan
Yeah you're gonna be very poor fuck using a device like that! Go and be a whining bitch somewhere else.
Could I use an extension cord for the secondary winding. I have lots of this wire but it has the neutral, hot wire, and ground wire in it. If I just twist these together will it still work fine?
Nice tutorial :)
I happen to have an old microwave oven in my basement, I'm going to give a new life using your video as a guide, thank you very much :)
No problem :)
@@Schematix gov will have all heads for this tech thay teach us that we always have loss but never talk about
the converted gain we can make from eletromagnets
if u convert all the wast thermal energy around
you u can use it universally as energy u need a true sine wave bipolar like the power comp dose a
true pure sinewave like a grid tie inverter
once the signal is made the system will turn on and
consume wast thermal energy from the
environment and space around you... there is free energy but it comes from Universal thermal loss and converted into a gain. so a pole Transformer and a
microwave Transformer have a common between each other u can take 2 microwave Transformer provide
a pure sine wave grid tie inverter to it or a true bipolar sinewave that inter acts with nature in
a perfect spherical motion like a flower of life.. if ur home provides this use it as a Source
signal then u can simply stack the Transformers on top of eachother in correct fasion and note
that the 1 wire on the Transformer must stay connected and the other disconnected your only useing
1 wire on the hi side .. so test ur self
2 microwave transformer stacked on top of eachother same face sides. one side 120 to the wall and the other 120 side to what u want to power and useing the
Transformer just the way it came out the microwave with the wire attached causes the energy in its
perfect spherical motion to converted wast thermal energy to amp for u hot to cold in to out...
should look a bit nuts with u use a form of wireless energy but its interacting with the environment...this is my work a compilation of Otis car. Tesla. and many other very smart people nowadays i think i found the gate source and drainif this gets out to much that it works the
power comp and mib will have our headsdont do this at home warning high voltage yet i cant stop u lol DO NOT TOCH THE CORES OR THE WIRES OK u will die make sure u dont touch the core if the hi wire is mounted to it u dont have to mount the hi on the core if u dont want u connect the 1 hi wire to the same side hi on the other transformer then the core should besafe to handle if nessary
@@Schematix gov will have all heads for this tech thay teach us that we always have loss but never talk about
the converted gain we can make from eletromagnets
if u convert all the wast thermal energy around
you u can use it universally as energy u need a true sine wave bipolar like the power comp dose a
true pure sinewave like a grid tie inverter
once the signal is made the system will turn on and
consume wast thermal energy from the
environment and space around you... there is free energy but it comes from Universal thermal loss and converted into a gain. so a pole Transformer and a
microwave Transformer have a common between each other u can take 2 microwave Transformer provide
a pure sine wave grid tie inverter to it or a true bipolar sinewave that inter acts with nature in
a perfect spherical motion like a flower of life.. if ur home provides this use it as a Source
signal then u can simply stack the Transformers on top of eachother in correct fasion and note
that the 1 wire on the Transformer must stay connected and the other disconnected your only useing
1 wire on the hi side .. so test ur self
2 microwave transformer stacked on top of eachother same face sides. one side 120 to the wall and the other 120 side to what u want to power and useing the
Transformer just the way it came out the microwave with the wire attached causes the energy in its
perfect spherical motion to converted wast thermal energy to amp for u hot to cold in to out...
should look a bit nuts with u use a form of wireless energy but its interacting with the environment...this is my work a compilation of Otis car. Tesla. and many other very smart people nowadays i think i found the gate source and drainif this gets out to much that it works the
power comp and mib will have our headsdont do this at home warning high voltage yet i cant stop u lol DO NOT TOCH THE CORES OR THE WIRES OK u will die make sure u dont touch the core if the hi wire is mounted to it u dont have to mount the hi on the core if u dont want u connect the 1 hi wire to the same side hi on the other transformer then the core should besafe to handle if nessary
Excellent explanation of how to get the voltage required from the mains but what about getting an exact amount of current?
Or is that way more complicated.
How do you get the right current
21 volts. What kind of amperage can you get out of your Transformer at 21 volts?
18:13 151 Amps
I was able to draw 10amps easily without any significant voltage drop.
bro what is the size of thhn wire you used for the secondary rewinding?? and i want also to know how much the a.c input of the primary in order for you to rewind the secondary winding..? thank!
Shunts are iron, not tin. Tin is soft and non-magnetic, and has a low melting point all the things you don't want in a shunt.
This guy is a Kiwi, so it is pronounced TUN, not Tin.
Hey sir what is the size of the red wire? Thanks
very helpful I am an electrician and have 3 microwave Transformers. And was thinking of making a welder.
Using number eight stranded silicone coated wire. Any thoughts ? someone told me the wire you wrap around The secondary should be in the same direction as the primary.
You can't make an Arc welder using a microwave transformer, it won't handle it.
You can make a battery nickel strip spot welder using 2, 3 or 4 turns of cable plus a timer trigger module designed for the purpose.
.
You need bigger than AWG 8 to get decent reliable welds. You might to it with 2 Or 3 parallel connected AWG 8, which will be cheaper and easier to wind than single AWG 4. Check the AWG cross sectional area specs chart.
.
You will struggle to get a MOT to do sport welds in steel. The main use is for nickel strips under 1.5 mm thick.
.
The direction of windings only matters if you are connecting more than one transformer in Series or Parallel. If they are out of phase, you got it wrong, so reverse connections on one transformer (You can reverse the primary if you like).
I thought I saw somewhere that there was a middle winding or something.
Good mechanical and electrical performance.
Best regards from the technical laboratory Ulm von Walter!
OK, nice enough tutorial. Question: Did you need 21 working volts? If so, throw on a couple more turns, as the voltage will drop when you add the load.
Also: Folks, please, if you're going to be teaching other people how to do things, at least use the proper tools. Screwdrivers are not drift punches or pry bars. Please show the people the proper tools to use for the job so they don't pick up bad habits from the start.
+LJ Prep
Please, if you are going to be telling people to use the proper tools - at least tell us what those tools are!!
:
@@criticallook1352 He used a screwdriver to pry. (I said they're not pry bars) He used a screwdriver to drive parts. (I said they're not drift punches) Now, if you can't figure out what the proper tools are, you have no business watching these videos. DIY is not for you. ;)
OL means open line, not overload. Why does everyone think that.
I saw microwave up the street I think I might go ahead and yank it.
I got a few Transformers around the house I think I might actually try winding one of them my battery charger just quit and it was taking a lot of current and I found that the windings for the secondary or absolutely crispy so I guess I might try to go to wine that really quick just for fun
Why manufacturers not using insulated wire like u did to wind transformers...this will prevent short circuit of transformer...i guess they don't want to run out of business
They do, it's called magnet wire and has a lacquer coating.
Great information as usual! Thank you for your excellent instruction! Thank you again. Joe
Would this transformer make a good inductor?
I kept hearing "I just did tin tunes on the secondary windings". Great video !
The letter E does not exist here in NZ. Just substitute every E with an I and you too will soon become a Kiwi.
Yeah us Kiwis are not too keen on vowels, so we decided to only use one. This is how you can tell us apart from the Aussies. They like vowels so much, that when they get to one they just hold onto it for as long as possible. Geeedaaaay Maaaaate.🤠
great tutorial! Saved me some troubles and just gonna re purpose my surplus of microwave transformers haha. Wish they made it so you could salvage and re purpose all of it. Having to cut it apart it kinda bad design tho I know why they claim to do it that way. =/
Oh also, my only critique for safety purposes would be when conducting the test to make sure the transformer isn't grounded, make sure to test that the place your grounding from is in fact a good ground contact point by touching lead to where you would like to have ground point and another random spot on the former with another. This leaves no room for error really. Or at least reduces it severly as I know I've had times where I thought I was on good grounds but was in fact weren't and double checking like that really saved me! Thanks again bud!~
This is not practical at all. This transformer gets Extremly hot under normal load. Because the input power is too much. I tried many time in the past to build high current power supply out of it, but no hope. Only you can built Spot welder.
OL is open loop
OL does not stand for overload.
OL stands for open line.
What is the significance of the shunts?
Any advantage or disadvantage to removing them ?
Lewis Balentine Apparently they limit the current drawn from the outlet during idle use and prevent the transformer from overheating
The shunts do limit the power to a limited degree. However, without them, most transformers will run much hotter and consume much more power even while idle. I don't really recommend removing them entirely. :)
I’m very late to this party. I hope you might find a moment to answer a question.
If you have rubbed the insulation off more than just one of the turns on the primary winding, is there any thing special you have to do to ensure they don’t touch under the lacquer insulation?
On rewatching I have a couple more questions:
1. Is there any advantage to making the wooden blocks more of an arc shape so the secondary coil turns are more circular as they pass outside the core from one side to the next?
2. Is the purpose of the shunts to add a ferric (“magnetizable”) spacing between the coils? Or are they there to reduce the air-gap between the coils, getting as much magnetizable material as possible between the coils?
the purpose of the shunt , it change the behaviour of the transformer from a voltage source to a not so good current source , it is needed because the magnetron act as a zener diode , if the shunt were not there hi line voltage ( input voltage ) would destruct the magnetron .
@@thecarl168 thank you Carl for that explanation. That is no doubt a very good reason to have the shunt.
There is a formula 4 the number of windings the primary and secondary. If you only change the number of turns on the secondary then the Transformer is no longer at Max efficiency. Am I correct? Another important detail I wish you'd covered was Magnet Wire versus insulated wire. I still learned a lot from the video. I really enjoyed it. Thank you.
What happened to the video of the power supply you used this transformer in? That was a great video.
He probably learned these transformers make for bad power supplies, you can't run them for very long before they overheat. As others have commented you need to add more primary windings.
Not a bad tutorial........for a Kiwi. Seriously though this is just what I was looking for as I have collected plenty of microwave transformers and I am looking to make an electromagnetic chuck/ machining plate. I had it pretty well sorted except for a power supply. I was looking for something around 40 - 50 volts dc but they are thin on the ground and as you said expensive but now you have shown me the way. I figure if I build a transformer like you have shown and configure it to put out about 35 volt Ac and then pass it through a bridge rectifier I should end up with around 42 v dc. Dc giving a stronger magnetic field. Thanks again mate. Cheers Stuart 🇦🇺
how you get 42dc from 35ac ?!
and i advise you to take many line from secondary so you get many ac volt
sorry about my stupid english
and did you know what wire gage or size he use for 15 amp ?
Fuorman. Hi Fuorman, I believe that when the AC goes through the rectifier you get an increase in voltage.
@@scroungasworkshop4663
Thinks for the idea
I will try it and tell you soon
I think diodes reduce voltage but maybe there's something i miss
Stay safe and take care my friend
Fuorman. I thought so to so maybe I am wrong. Please let me know how it goes. You stay safe as well my friend. Cheers Stuart, Australia 🇦🇺
@@scroungasworkshop4663 AC voltages are usually given as RMS while the peak is ~50% higher, eg 240v has a peak of 325v. Your bridge rectifier converts peak AC to DC, so it comes out higher. The bridge has 2 diodes and will drop about 0.6v each.
RMS is the DC equivalent of peak AC, so a resistor at 325v AC (peak) will put out the same amount of heat as one connected to 240v DC..
What's the no load core losses?
trash to treasure? what trash
In my country you have to recycle all electronics, its forbidden to dispose a microwave with household waste. Even at the local recycling center they do not allow you to take an old microwaves with you. My only source for transformers is eBay. Good for the environment, bad and expensive for DIY :-(
+Lejf Diecks
You may find used microwave ovens in stores that sell used equipment, Also ask in stores that sell new appliances, they always have access to 2nd and 3rd Quality appliances from distributors.
Also ask in any TV repair workshop.
Another option is to place an advertisement in the local newspaper, stating that you collect used microwave ovens, and you will have more transformers than you will know what to do with and a lot more useful parts ---
How can I make full waves transform. Like 25-0-25 ac volts. Thank you.
How can I make a full wave transform, like 25-0-25 volts ac. Thank you.
Anyone can answer me. Thank you.
Why use the shunts ?
Hello my friend.
Your video is very detailed and I watched it with great interest. Long ago I saw a video of you in which you used this transformer to make a laboratory power supply.
I'm trying to find this video, but I can not find it.
Can you send me the link?
What size of wire did you use for the secondary winding
Korvah yeah, I'm wondering the same thing, what about it Schematic?
He said 15 amps so it would be 14AWG, #12 will be good for 20 Amps, #10AWG for 30 Amps
What is the idle current of this trafo?How fast it going to heat up at light load and maximum load?
Very good point. No one pointed it out
hello schematix i want wind a ferroresonant transformer CVT 220 volts using microwave transformer can you help me ????
I would like to build a 12/24 Volt charger/ jump start for my tractors. Would you be interested in showing how this could be done? Thanks, Randy. We are at -49* below up in Canada right now and always in need of such boosters during winter. They want over a thousand dollars for one. I even have quick connect heat lines between motors but when the batteries are down you’re done.
Thanks, awesome vid.
Q With the secondary, you did a test of 10 wraps. Did you join those first 10 wraps to make your end result of 20+ wraps? If so how would you do it. Cheers
Glad I found your site.
Thanks for the feedback. There is no joins in my secondary. It's a continuous length of wire. I tested with 10 turns and left the remaining wire on the spool I was feeding from. That way I didn't have to cut the wire :)
Thanks mate, your a natural teacher. Cheers
What gauge wire did you use for the secondary winding? I'm in the U.S., which is likely a different standard, but I can figure out the conversion. Thank you!
The wire I used works out to be around 12AWG. As long as you buy wire that can handle at least 15~25 amps it should be fine.
if you draw 15 amp it will melt thanks to the tick insulation on the secondary get some real transformer wire, look for company's who are rewinding electric motors.
It would be cool to turn this into a bench power supply unit.
I've just stripped our old microwave. I'll sell the magnatron on ebay and re-wind the transformer to give an output of around 7V reg/rec down to 5VDC to power the auxiliary circuit on my model railway.
Just a word of warning. Be very careful when dismantling a microwave oven. There is there is a massive capacitor, which can hold a lot of current. If its still holding its current it can kill you. Be Especially careful with older models, newer models should have a bleeder to slowly bleed off the current. Just be careful and watch out for this capacitor and you should be ok.
P.S. It is best to wait until the missus has finished cooking her 2 minute noodles. Ooh and don't forget to unplug it before dismantling.🤪
OL stands for Over Limit NOT OVERLOAD.
Science-is-god
Which means the same whining little bitch!
What happen to the power supply video
Build a Rather Hefty Battery Charger doing this. Was able to start my truck engine using the thing. Did just fine cranking the engine for a few seconds at a time. Any more then that and it would have melted down I'm sure but it worked.
I will try this but I'm going straight to cutting the secondary coil with the hacksaw. I'm skipping the step of removing the shunts before removing the secondary. I'm hoping the shunts are easier to remove after removing the secondary. [Oh!] Now I see the secondary is glued in place as you said and the shunts prevent levering it out. Okay. Nice work. Thank you.
Really good information, nicely presented. I have one constructive comment: You need to open your mouth more when speaking. You are quietly spoken (as am I), and therefore we need to open our mouths a little bit more when speaking so it's clearer. It could be nerves too - was that your first video? Anyway, good job overall.
hi thanks for this....advice= use an angle grinder, (i use homemade steel chopsaw 14 inch)to cutoff secondary.Shunts are needed in the redone core, as well, to separate magnetism. Also, a ground down railroad spike works best, to hammer out secondary core...fits like a glove. I've done many of them.......alternatively, also grinding off the welds, and take-apart the core.....works as well....then, weld up when done winding secondary bobbin.....
no way jose on that pricing,not sure where u would get ripped off for 100 to 200 for just one transformer when u can once again go on amazon or find used ones complete for $50. used ones for hamradio etc can go from 50 to 150 and 20 amps complete ie Pyramid or astron supplies,but dont misunderstand me,this is all good hobby work
Hey man!! Awesome video. I'll be doing this to power an electrolysis chamber to launch marbles in my "marble machine".....very informative, thanks!! I see lots of interesting videos on your site, and I just subscribed!!
What is the load voltage/current for the maximum power output of the rewound transformer?
Hello teacher, yes this old man has understood you more then others, im hopeing please youd help me a bit, Thank You . Im wanting to make a 25 amp battery charger and ive watched a few vidieos on the channal and not getting all i need to know or understand, showing my lack of electrical knowledge i first missed you ground to the outside of the transformer, does it also connect to the other terminal or the primary winding ? into the power supply 220 ? earth ground im told here in the philippines. Make a Long story short on you , Would Be beautiful to see a vidieo of you builing one, i dont know what size rectifier or other components / n rateings needed. If you find time please be my guide. Thanks Really and thanks for the smile with your humor with infected /effected :-)
Thanks for the video.How many meters did you use on the secondary, for 12AWG cable ?Thanks in advance.
You're welcome, I bought 10 meters and used most of it. Depending on the size of the core, as a guide each turn uses approx 300mm of wire.
Hi again.I just rewind the Transformer, but the core heats up without any load. Whats the reason? Thanks in advance.
Most transformers will be warm without any load. In simple terms you have to remember the primary winding is effectively a wire wound resistor between live and neutral and will always use some limited amount of energy even while no load is being drawn on the secondary. How hot the transformer gets does depend on a number of factors. I've got a couple commercially made transformer that easily break into the 50 degrees celsius mark. However If your transformer is too hot to touch there maybe a problem
Yes it might be around 50'c without load. Thanks for the information.
I want this
nice video I tried to make a spot welder. For it i bought a used MOT, the seller connected ac voltage to the primary winding (thin wire side). And it created humming sound. At home I removed that side and when I connected ac to the secondary side it created smoke and smell and became very hot to touch. Seems like the Secondary was already short? What you say?
Also Now can i rewind it using suitable size enameled wire? Will winding it with slightly thinner wire be ok for spot welding? Current winding is using 0.9mm enameled copper wire and the length and breadth of cross sectional area is 15 by 17 mm..