This is an amazing induction heater and now you can build your own for fun or as a powerful tool. I have put together an extensive tutorial at http://inductionheatertutorial.com with schematics for building a 3 and 12kw unit. You'll be able to instantly melt steel aluminum and copper. You can use this for brazing, melting and forging metals. You can use this for casting, too. The tutorial covers theory, components and assembly of some of critical components. The tutorial is large. I will go over the main steps here to give you an idea of what goes into a project like this and how to design it so you don't blow any mosfets or IGBTs.

If you wish, you can refer to the link above. This Instructable presumes you have a good understanding of electronics and induction heaters. Let's begin.

As an aside, I have put together a very accurate low-cost cryogenic digital thermometer. Watch me put it up against a standard name-brand using liquid nitrogen for the test.

Step 1: Components

The basic components are the inverter, driver, coupling transformer and RLC tank circuit. I'll show you the schematics in a little bit. Let's start with the inverter. This is an electrical device that changes the direction of DC current to AC current. For a high-power unit this must be robust. Above you can see the shielding that is used to protect the mosfet gate drive from any stray EMF. Stray EMF causes noise, which results in high-frequency switching. This leads to overheating and failure of the mosfet.

The high-current traces on the circuit board are underneath. Many layers of copper are used to allow them to carry over 50A of current. You do not want them overheating. Also note the large aluminum water-cooled heat sinks on each side. This is needed to remove the heat generated by the mosfets. I originally used fan-cooling, but to deal with this power I have small pond pumps moving plain water through the aluminum heat sinks. As long as the water is clean there should be no conduction. I also have thin mica pads underneath the mosfets to ensure there is no conduction through the sinks.

<p>Congratulations for your work! </p><p>However, looking at your PLL <br>schematic, all grounds have the same symbol (meaning there are connected<br> together). In that situation, using two 2A output optocouplers hasn't <br>too much sense. You've connected pins 3 and 5 to the same ground. In <br>this configuration the optocoupler does not reject any noise, it's just a<br> redundant device. Eventually, to keep clean the signal, it has to be separated <br>ground between PLL and inverter... Do I miss something?</p>
<p>Trying to build this for my FRC Robotics Team. Including the Levitation posting there are 3 versions for the sensor! The Lev. says hook to probes or Microprocessor, which is what I was looking for. Is this in place of, from tank capacitor or what? As I am a coder, I can muddle through that, but electrical engineering is not my strong suit. Thanks</p>
<p>The sensor gives a reading of the AC current waveform that drives the coupling transformer connected to the RLC tank (the part with the Celem capacitor and work coil). This is not necessary to get the circuit to work: it provides information on the proper function of the system. Knowing this, I attached a diode and smoothing capacitor to a DC ammeter to get a constant analogue reading of the current. This is important, because if the current gets too high I know I will overheat the mosfet switches. For the smaller circuit this was about 20A; for the 10kw units this was about 50-60A for short periods. I used a voltage divider to feed the current value into the uProcessor and wrote a subroutine that constantly monitored the current. If it got too high I detuned the circuit to reduce the current. This is useful if the workpiece falls out of the coil. When this happens the current shoots up without anything to quench the tank. Having this feedback I could quickly reduce the current and protect the mosfets. I was thinking of producing a second generation board that would also get input from a thermocouple connected to the mosfets and would shut the system down if the temperature got too high. I never did it as I sold my project to a blacksmith.</p><p>I hope this helps. You can go to my site http://inductionheatetutorial.com for a little more information.</p>
<p>Really confused? This page shows a current sense transformer connected to nothing, while the tutorial shows a pulse transformer connected to a meter at the same place. What does the sensing transformer do here? So, same question as before. Oh yeah, Happy New Year,Thanks</p>
<p>Missed that as I'm designing around 2 HB IGBT, and didn't look closely. Was hoping a current sensor might be useful in a self regulating ppl circuit. Thanks</p>
<p>Been struggling with your driver design. The schematics and photos don't match, ie: a sensing transformer that's nowhere in the schematics? Real schematics of your current design would be really useful to all of us. Thanks</p>
<p>If you look at this schematic from my tutorial website</p><p><a href="http://inductionheatertutorial.com/inductionheater/inductionschematic.gif" rel="nofollow">http://inductionheatertutorial.com/inductionheater...</a></p><p>the sensing transformer is there on the right side.</p>
<p>if I were to put this around a hose, would it heat up the water?</p>
<p>HIiii your project very interesting. I have one request please discuss the proper designing of that capacitor and inductor(toroid ) which used in this proect </p>
I'd love to make the 3k version of this for my AP chemistry class and to use for casting, but I can't find where to get the supplies. I've read through your website and you mention the suppliers, but don't really mention the model/size/ capacitors and such and specifications of other parts. I'd love to see a total list of necessary supplies and hardware but I'm having no luck so far. Thank you and I really appreciate it!
<p><a href="https://www.instructables.com/member/imsmooth" rel="nofollow">imsmooth</a> (author) <a href="https://www.instructables.com/member/transistor2" rel="nofollow">transistor2</a><a rel="nofollow">Reply</a>2 years ago</p><p>3kw is about $300</p><p>12kw is about $1000</p>
<p>Could someone throw together a parts/cost list? I need to know the grand total before I commit too much time to this project.</p>
<p>Thanks for posting this, it's detailed enough and in laymans terms so that with my very limited understanding of electronics I can almostttt understand how this induction heater works lol. I'm actually very interested in trying to build a furnace similar to yours to use in a hobby foundry. I'm curious how much steel can be melted in the 12KW version. I'm hoping to be able to melt 3 quarts of steel at a time. Will this design be able to melt that much? </p>
<p>Simply ATtiny10 or 13 could also be implemented for generating frequency with fewer external components.</p>
<p>This will not have the fine resolution compared with writing directly to the clocking center.</p>
<p>I have been looking for some more information about your driver, it seems strait forward expect the program, sketch you make for your arduino. I found some old forums you've posted on but nothing useful to me. PM me or email me if you don't want to make it public,</p><p>I'm looking at yours as an footstep to use for the 30Kva induction driver. I know some modifications are needed but starting with the knowledge of your driver is a great asset </p><p>For credibility this is my website, <a href="http://skydom.weebly.com/creators--partners.html" rel="nofollow">http://skydom.weebly.com/creators--partners.html</a> and I'm making this on behalf of a makerspace i am with. </p><p><br></p><p>the sketch for the arduino programming is all I really need </p>
<p>He is sharing so much because he knows it makes us happy. How do you mean induction driver? You don't really want this for a rail gun there are already lots of guns.</p>
<p>Looks like a great design.</p><p>Maybe I'm missing something, I do not find the software for the Arduino. Is this part of a separate project? Can the functionality be done with hardware?</p><p>Thank you.</p><p>Erik</p>
<p>Never published the code. The tutorial explains what is required. One will need some experience with a uP to follow the directions in the web tutorial at inductionheatertutorial.com</p>
<p>Would you please post a detailed shopping list for the whole project?</p>
My tutorial website has much more instructions and explanations.
<p>i've always had this one confusion... making the current flow through a loop of wire is like shorting right? why doesn the circuit blow up?</p>
<p>It is true what you say, a loop of wire is like a short, but once a piece of wire is formed into a coil, it gains the ability to store energy. What we have now is an inductor. An inductor is capable of storing energy in a magnetic field who's direction can be calculated using the right hand rule. Further, an inductor contains a type of 'resistance' called impedance. It is also measured in Ohm's, but there are some complex components involved making it hard to explain without relatively advanced calculus. This resistance would make the inductor a 'load' and therefore it has the ability to dissipate energy, mainly through heat. This keeps the circuit from 'blowing up' as you put it. </p>
<p>Noah nice :D</p>
<p>Any way I could get a parts list? I would love to make one of the 3k ones</p>
These are amazing! I just saw a video about a levitation induction furnace and was blown away. You just reverse the coil halfway apparantly and the metal floats untill you turn it off.
<p>Hello I found your project very interesting. I have some question: are capacitors of 0.22 uF really necessary ? Could be all avoided ? Is the series capacitor in the work coil circuit really necessary it should manage a huge amount of current. Last question is : could a H bridge bring advantages too this inverter or has not any meaning ?<br>Thanks. </p>
The h-bridge adds more mosfets and cost without any great benefit.<br><br>If you go to my website you'll see why the 0.22uf caps are needed.<br><br>Go to inductionheatertutorial.com
<p>You are right, but often mosfets can cost less than good quality snubbers/capacitors. Anyway it was only an idea.</p><p>...Ok, I understand that 0.22 caps are needed for a sine wave &quot;production&quot;; but is the cap on the secondary (in series with the work coil) really needed ? </p><p>Thanks.</p>
<p>hi</p><p>thanks for your article</p><p>the schematic picture isn't clear</p><p>i can't find details on the schematic</p><p>please send me your schematic,it's very emergency :D</p><p>at last i wish secsusfully for you </p><p>mail:sin.majidi@Gmail.com</p>
<p>How do you prevent the cooling water electrolyzing and corroding the tubing? When I built a 4KW heater, I ran the water through the secondary of the transformer (one turn sheet brass 4&quot; wide 3&quot; diameter), then through the work coil. So there was no voltage applied to the water, other then a small resistive component.</p>
There are no dissimilar metals<br>Only copper<br><br>The aluminum heat sink has its own cooling system
My question is not about 1 or 2 volt galvanic potentials, it is about applying many volts to the water (copper sections of the cooling system are at different potentials, and have the same water flowing through them, correct?)<br><br>If you feed water through the work coil (in one side, out the other side, returning to the same reservoir), the voltage on the secondary of the output transformer is applied to the water (unless you do as I did and run the water also through the transformer secondary).<br><br>High-power lasers had this and the water was carefully deionized, but it corrodes anyway.
<p>With my nonexistent knowledge of electricity theories and all, I can finally do my induction heather for forging, really tired of the fossil fuels. We all like the old touch of a steel rod getting heathed on a furnace, but this is way more practical, space saving, kinda enviromentally friendly, only using home voltages. Thanks for the tutorial man.</p>
<p>Wow, this is some heavy electronics. I'll put it in the todo list since I have other business now, but my compliments on your design. Nice to see so many DIY initiatives.</p>
<p>Very cool instructable, but please be careful dropping the molten metal out on your concrete floor. Any water content in the concrete can rapidly (read: explosively) turn to steam and fail catastrophically.<br>I would recommend getting some inexpensive firebrick for collecting the metal ejection.</p>
<p>Wow this give a person the insight on how the inverter welding machines work! They are light and give excellent resuls</p>
<p>Wow this give a person the insight on how the inverter welding machines work! They are light and give excellent resuls</p>
<p>I'm guessing by the look of it that the Working Coil is water cooled too, is there anything that needs to be taken into consideration between a dry coil and one filled with water as far as design.<br><br>Do you have to use distilled water or anything?</p>
<p>I just addressed this in the instructable. I just use plain tap water. Make sure it is clean, meaning does not have a high mineral content which could make it conductive. I one pump to run water through the mosfets. Each mosfet has a mica pad isolating it from the cooling sink. I use another pump to run water through the capacitor and work coil. This is a large multi-gallon bucket of ice water. You can run this water through a radiator if you wish to disperse the large amount of heat the work coil generates.</p>
<p>Thanks for taking the time to answer. :)<br><br>Yeah I was thinking about possible conductivity issues, or changes in inductance, that sort of thing.</p><p>Separate cooling for the Mosfets and the working coil makes sense too.<br><br>Cheers!</p>
<p>how much does this cost to make</p>
<p>3kw is about $300</p><p>12kw is about $1000</p>
<p>That thing is scary! Awesome job.</p>
<p>nice pro</p>

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