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Step 7: Testing and Usage

Assemble everything according to the schematic. Use a current transformer on the primary side (100t burdened with a couple ohms around a ferrite toroid will do) to monitor the waveforms.
Using a current-limited bench supply (preferably 30V, 10A), slowly ramp up the voltage until enough current is drawn to give a clear reading on the 'scope. Adjust the frequency pot until the waveform is a clean sinewave, and current draw is maximized (you may have to search a little to avoid harmonics). If you don't have a scope, just tune until current is maximized (mine drew something like 40A at 200VDC on the bus, unloaded).
With ~30V on the bus, load the work coil with a bolt. At a few hundred watts in, it should get hot within a couple minutes. If it draws power, but the workpiece doesn't get hot, check the transistors for heating. If they get excessively hot, your bridge is shooting through.
If all is well at low powers, you are ready for a high-power test. Use your favorite DC source (single phase, three-phase, smoothed, unsmoothed, etc - it doesn't really matter) to power the bridge. Preferably, use a Variac, in case it draws too much current (you can predict current draw from the low-power tests by noting that the heater is a fairly linear load). Don't forget water cooling!
At a few kilowatts, without a crucible, you can melt aluminum and copper and make steel orange-hot. 10 KW+ (50A dryer/stove line or 3-phase) is necessary to melt steel in open air. A crucible helps a lot.
You can control power by very slightly detuning the inverter, or by changing the bus voltage, or by tapping the matching transformer. The latter is a recommended feature, and steel and copper have very different effective "resistances".
Good luck, and have fun!

<p>I really would like to view a schematic. The version in this instructable is such low resolution that I cannot see values of the components. Could you either email one to me, or better yet improve the quality of the one in your instructable so that everyone could see it?</p>
<p>This looks like a great project! Could you please send the schematic? Thanks./ds</p>
<p>Hi,</p><p>Nice build!!! Would it be possible to obtain the schematic? Thanks.</p><p>dturnbull316@gmail.com</p>
<p>Hi thanks for the project, I just had a question on the gate drive stage 2, you added a second capacitor on the circuit as C2 but it doesn't have a value, and in the Eagle schematic it isn't even mentioned. So I was a bit confused, thank you!</p>
<p>Hi! I would like the schematics if possible!</p><p>carrillo.joseph.r@gmail.com</p>
Would like the schematics please. <br>jeffmiles1@yahoo.com
<p>Sorry for the stupid question, no reply necessary. Answer; self wound isolation transformer, 10+10. I should read the text more carefully and not just stare at schematics. Thanks</p>
<p>Hi, building a furnace from CM600NFH's, hope to debug the ATmega controller. Till then would like to run it off your design, but have one question; the blocks between the drive stages and power are 1:1:1 couplings? Don't want to assume. When I work out the controller I'll post it, unlike ReactorForge. What a DIY cop-out they are. Thanks</p>
<p>Hi,</p><p>I am interested in building the similar schematic. I am wondering if the schematic is similar with the AC motor controller?</p>
<p>Hi,</p><p>Interested in getting the schematics</p><p>yousif1966.2@gmail.com</p><p>Thank you</p>
<p>Hey there,</p><p>Interested in building this design.</p><p>Was wondering if i could get the schematic</p><p>bensonr08@hotmail.com</p><p>Thanks</p>
<p>Hi,</p><p>Interested in getting the schematics</p><p>andrewholden00@gmail.com</p><p>Thank you</p>
<p>HI,</p><p>Can i get schematic?</p><p>My email is <a href="mailto:daehyunele@gmail.com" rel="nofollow">daehyunele@gmail.com</a></p><p>Thank you..</p>
<p>my email mohammad.daryono@gmail.com</p>
<p>hii </p><p>Can i get all schematic,pliiis</p>
<p>Hello ...... my dear friends extreme need and schematic circut this Please if anyone's got the induction furnace Send me anymore&lt;enginervaziri@gmail.com&gt;</p>
<p>Do you have a ballpark estimate of how much the total bill of materials costs? I don't need an exact number.</p>
<p>I have approximately ten toshiba MG200q2ys40 half bridge igbt modules 1500 volt 200 amp for $75 a piece if anyones interested. email me Andrewboerder@gmail.com</p>
<p>All the schematics please! asraith@gmail.com </p>
Good day <br>I am interested with your estimated induction heater so I hope you send me the schematic circuit <br>Thanks a lot
<p>hi </p><p>can I get circuit schematic?</p><p> jformm3@gmail.com .<br>thank you</p>
<p>HI, can I get circuit schematic? My email is anpaguiar@gmail.com</p><p>thank you</p>
<p>HI, can I get circuit schematic? my email id is prashantgauravbaghel@gmail.com.<br>thank you </p>
Hi can I get the schematics my email is benngalaska@aol.com thanks!
Hi, I want to make this project. You can send me its schematic to this email : shivana.5511@yahoo.com<br>
<p>Hello,</p><p>I was wondering why the ferrite toroids for the coupling transformer are so large?! Wouldn't it be better to have toroids with a smaller diameter to reduce magnetic losses?!</p>
<p>Magnetic losses occur more with smaller toroids because magnetic saturation occurs faster with a smaller amount of iron</p>
Ok, it makes sense...thank you for your reply.
<p>anytime</p>
<p>By the way, I would have another question if you don't mind...maybe you have an idea.<br>I saw a comment from lavila540 on this page who ordered the following ferrite cores for his induction heater:</p><p><a href="http://www.mag-inc.com/company/news/new-4-inch--kool-mu-toroid" rel="nofollow">http://www.mag-inc.com/company/news/new-4-inch--ko...</a></p><p>But I would aim for those cores (with the P material):</p><p><a href="http://www.mag-inc.com/home/Advanced-Search-Results?pn=49725" rel="nofollow">http://www.mag-inc.com/home/Advanced-Search-Result...</a></p><p>where the inductance and permeability are much higher. But in the first case they call it the &quot;Kool Mu Permeability&quot;...so is there a difference with a &quot;normal permeability&quot;?! I am a bit confused...<br>What would be the most important characteristics to look at?<br><br>Thanks</p>
<p>do the ferrite cores have to be that large?, I am having difficulty finding any that big here in the UK</p>
<p>I bought mine last week from mag-inc. I`m in the US but, they might be able to ship. Seen some one e-bay too. </p><p>http://www.mag-inc.com/company/news/new-4-inch--kool-mu-toroid</p>
<p>Hello lavila540,<br>Have you finished your induction heater? Does it work well?<br>I was wondering why you chose these ferrite cores? Is it working well with these ones (no heating)? What is the most important characteristics to look at?<br>Do you think these ferrite cores might work as well:</p><p><a href="http://www.mag-inc.com/home/Advanced-Search-Results?pn=49725" rel="nofollow">http://www.mag-inc.com/home/Advanced-Search-Result...</a></p><p>I'm aiming for the P material. But comparing yours and these ones, the permeability and the inductance are much different...I am confused...<br></p>
<p>Greetings,</p><p>Is it possible to get the schematics emailed.</p><p>jeff@fd-intl.com</p><p>Thanks</p>
<p>If possible, I would like receive schematic diagramms by my e-mail.</p><p>FYR, e-mai address is <a href="mailto:franzhwang@hanmail.net" rel="nofollow">franzhwang@hanmail.net</a></p><p>Thanks</p>
<p>i want document. you can send me? please...</p><p>sarawut262535@gmail.com</p>
Where is your scmatic? <br>I want to build a very small one
<p>hello </p><p>need to circuit diagram to progect </p>30 kVA Induction Heater
<p>what is the current going into the tank? The capacitors I have found by Eurofarad have been rated around 150 amps max. After the current is stepped up by the coupling transformer won't the current exceed this?</p>
<p>Not sure if you know, but if not then your work has been stolen:<br><a href="http://ofslides.com/bwang-546040/presentation-1019981">Check here</a><br>Brooklytonia found the website and opened a thread about it in the forum as well.<br>However, if that is something you published there yourself forget about it ;)</p>
<p>I'm wrong-1,800,000 VAR=1,800KVAR.If I'm getting 400 amps to the work head than the tank circuit should have unreal current in it,I can't even calculate it!</p>
<p>My system will be operating at 30khz with 1.92 microhenry work coil with 1/2&quot; tubing I believe I will sweat 56% Silver solder onto .This F0 will not over drive the IGBT's and create great penetration.I Should have many thousands of amps in work coil with Q of 126 icrease in input tank current.</p>
<p>I'm building my system around 4 600 amp Powerex's and BG1A gate drivers.I have a 16 tap 800KVAR workhead.My main tank capacitor is 15uf at 6kv,300amp oil filled capacitor rated at 1,800,000KVAR,weighs about 30 pounds! I am driving the inverter with a 130 vdc at 400 amp military grage generator and a 60 hp Suzuki samari engine.This gives me This gives me 52,000 or 52 kiolwatts of power to work with.This should defiately smelt a little steel?</p>
<p>Okay, bare with me because electronics is far from my field of expertise, and I have a few questions I'm hoping someone can help answer. </p><p>First, why is it necessary to have a rectifier (its not really mentioned) if we are just going to reconvert the signal back to AC? I'm guessing that a DC source is needed for the input to the IC which is the oscillator which then drives the gate drives, the power stage and eventually the tank circuit. That being said it also appears that the rectifier is wired directly into the IGBTs, is it necessary to use DC to drive these? Am I on the right path with any of this? </p><p>Second, it's stated that the the frequency and dead time of the oscillator can be controlled, but how exactly? How is the frequency of the AC current in the tank circuit actually controlled? </p><p>Lastly, what is the function of the input capacitor and why is it necessary? There's no mention of it other than in the picture at the beginning. </p><p>If anyone could take the time to explain these things to me I would really appreciate it. </p>
<p>Going another direction, I want to anneal brass tubing. I'm *trying* to build something that will heat rifle cases to around 750*F. without over annealing them, and do it in a very short period of time so I can maintain production volume.</p><p>This takes a coil that is open enough for the brass to enter on a belt/conveyor and exit the same way, so the coil is longer, oval with the ends bent up to allow for brass to pass into the induction coil, and out of the induction coil as it proceeds down the production line.</p><p>I CAN regulate the belt speed through the coils... And I can get the coils very close to the brass, but what I'm having an issue with is the amount of brass moving on the line (Mass) and building an inductor with enough power to make the brass reach the designated 750*F.</p><p>With rifle brass, It's a pretty good conductor, so it doesn't heat as fast as steel, and I'm not trying to anneal the entire brass, just the top 3/4&quot; or so... But production still puts a lot of brass in the coils at one time, so the heating is VERY slow, which leads to thermal transfer down into the case body/bottom, which I DO NOT want. I would rather the sides/bottom stayed under 450*F.</p><p>I'm considering a water bath for the bottom of the cases, which is going to add more mass and slow the induction heating of the top of the brass...</p><p>Since this is for a high volume competition shooter (100K rounds/year), and not a business, I would be glad to pay a REASONABLE amount of money for someone that can help address these issues.</p><p>I've seen the high volume MANUFACTURERS have induction heaters that would knock out the entire process in just 3 or 4 seconds, I'm not looking for something that draws 440 volts AC and spins the electric meter off the side of the garage, but I would consider 220 VAC single phase, providing the unit works efficiently and doesn't cost a fortune to build or operate...</p><p>Anyone got any ideas how to build something that doesn't bust the bank?</p>
<p>I'm sorry to disappoint you a little bit, but there's one caveat to your water bath plant: all the copper alloys are not only good electrical conductors, but good heat conductors as well (there's a reason why all the high-quality heatsinks are made either from pure copper or aluminium with a copper core just above the CPU). Thus if you'd add water to any parts of the brass casing, you'd make it even harder for it to heat up to your desired temperature of 750 &deg;F, because water is a VERY good coolant (it has one of the highest heat capacities of all the fluids).</p><p>Since there seem to be no 3-phase electric outlets installed in US homes at all for some strange reason, I'd recommend you obtain some REALLY high amperage outlets for this project (a 100A one would get you reasonably close to the 30 kVA mentioned in the project). Moreover I'd also consider lowering the frequency a tad bit (no more than 10-20 kHz tops), get a bit smaller pipes, wind them in very close loops (while making sure that the loops are adequately insulated from each other e.g. by a lacquer) and wind multiple loops on top of each other (this increases inductance a LOT). All of these things (and probably quite a few others folks more knowledgeable about this topic than me perhaps know about) are just tweaks though: the main issue is that you MUST deliver more energy to your brass cases than necessary for heating them. Frankly if I were you I'd just use some heating elements instead.....</p>
<p>Im thinking if i skipped the rectifier in this, could i power the bridge directly with a 3 phase, 400V stick welder with some unknown DC output at 150A. ??</p>
<p>Not that I'm aware of. I'm not sure whether there are any welders on the market that could supply 30 kVA of power. Even on 400V (3-phase) level that's 75 amps. On the voltage levels typical for welders (like those 20-40 volts mentioned above) you'd need the welder to supply AT LEAST 750 amps (not accounting for conversion losses of course). It goes without saying that such welders (if they even exist) are ridiculously expensive. So expensive in fact that you'd be better off even commissioning some freelancer (or a local EE student) to build this PLUS paying the whole BoM than buying an appropriate welder that'd supply the required power.</p>
<p>Not really. Welder voltage too low and not stable at all (usually 70 or so volts with no load and 20-40v at that 150A). Sure you can run 350v-400vdc circuits on 35-40vdc but at only 1% the power since then it will also be at 1/10 the current. 300 VA might get a small 1/4-20 screw hot, but why build all this just to do that? That's like buying a Ferarri but never driving over 55mph.</p>
<p>could you send me the schematic? may email: nguyenhuanute</p><p>@gmail.com</p>

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