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Introduction

Induction heaters are used to heat conductive materials in a non-contact process. Commercially, they are used for heat treating, brazing, soldering, etc., as well as to melt and forge iron, steel, and aluminum.
This Instructable will walk you through the construction of a high-power (30kVA) heater, suitable for melting aluminum and steel. Note that to take full advantage of this design, you will need a 220V outlet, at least a 50A single-phase one and preferably a 50A or 60A 3-phase outlet.

About the author:

Bayley Wang (me) is a EE student at MIT. I'm responsible for a variety of nefarious power electronics projects which you can find on my blog; perhaps most interestingly is oneTesla, which has since gained a life of its own as a startup creating DRSSTC kits.


WARNINGS

  • This project uses mains voltage. While well-behaved, 110/220 mains can seriously injure, maim, and/or kill you if used improperly.
  • The voltage across the tank capacitor can potentially ring up to hundreds of volts. Don't let the 20:1 step-down ratio fool you!
  • When scoping the circuit, beware of ground loops.
  • The work piece, naturally, can get very hot. DO NOT TOUCH! Less obviously, do not rapidly quench the work piece with water, as this can lead to dangerous sputtering.
  • This project uses power electronics. Under fault conditions, semiconductor devices used in this project may rapidly heat, vent, and/or release rapidly moving shrapnel. Shield appropriately.

WIth that said and done, let us move on.

 
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gdawg981 month ago

How much steel can I melt say if i make a crucible for it and keep all the heat in can I melt 40kg of steel

not with 30kVA. Maybe 10kg and that takes some doing like vacuum insulation (impractically expensive as the ceramic material has to hold a vacuum as well as withstand 3000F). For 40kg might as well stick to an acetylene-fueled kiln.

AndreasP814 days ago

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. ??

Lets JustB4 months ago

Here are the photos of what i have done.

2015-04-12 14.23.01.jpg2015-04-12 14.23.12.jpg2015-04-12 14.23.26.jpg2015-04-12 14.23.45.jpg2015-04-12 14.23.56.jpg

hi

I need some one make for me induction heater. i want to heat pipe 10 inch diameter, if u can do it send me mail bbtec3d@gmail.com. if it ok may i will buy from u hundreds

rezay2 months ago

l making induction heating now

I send photo pictur yourself

BbtecI rezay1 month ago

I need some one make for me induction heater. i want to heat pipe 10 inch diameter, if u can do it send me mail bbtec3d@gmail.com. if it ok may i will buy from him hundreds

BbtecI1 month ago

I need some one make for me induction heater. i want to heat pipe 10 inch diameter, any one can do it send me mail bbtec3d@gmail.com. if it ok i will buy from him hundreds

BbtecI1 month ago

I need some one make for me induction heater. i want to heat pipe 10 inch diameter

gdawg982 months ago

How much steel ca you melt with this if you use a 10 kw furnace

Lets JustB4 months ago

Here is the waveform when is comming out of the ucc37322 before it goes into the toroid. Also i used an arduino as a PWM generator there is a photo of it below here is the code

void setup()

{

pinMode(8, OUTPUT);

;

}

void loop()

{

digitalWrite(8, HIGH);

digitalWrite(8, LOW);

}

2015-04-13 17.29.42.jpg2015-04-13 17.29.48.jpg
Lets JustB4 months ago

I found out a few things since my last post. The first thing was that the PCB Layout was incorrect on the oscillator PCB. On the ucc37322 the pins 2 and 3 should be connected together or the bottom one connected to 5 volts.Also the little ucc37322 chips short out really easily don't connect the oscilloscope all the time without thinking also don't connect the oscilloscope when the first PCB is connected to the second PCB through the toroid. Check the wave form coming out of the ucc37322. you should only check this when the toroid is not connected though or on the seondary coil when the second PCB is not connected. the image below is the waveform coming out of the second PCB with the mosfets. (also with the toroid i used one out of a microwave the other one i bought from JAYCAR did not work at all the wave form of that one was really bad and not square at all. (this is before it is connected into the second PCB.))

2015-04-13 17.09.05.jpg2015-04-13 17.09.10.jpg2015-04-13 17.09.18.jpgmissing 5v.jpg
Lets JustB4 months ago

I took 5 Wires of Cat 5 and wound them around the toroid (ferrute Core) od 35 mm ID 20mm 13mm thickness.I have wound the wire round 15 times and all the wires are twisted together i did this with a drill. I put 15 volts into the circut and Just get noise out.

2015-04-12 14.34.12.jpg2015-04-12 14.34.35.jpg2015-04-12 14.35.12.jpg2015-04-12 14.35.35.jpg2015-04-12 14.35.50.jpg2015-04-12 14.36.02.jpg2015-04-12 14.36.22.jpg2015-04-12 13.24.26.jpg
Lets JustB4 months ago

After building the first PCB It appears that it does not work i have connected an ossisliscope up to it and all i get is noise. I am not sure it is a real circut.

Lets JustB4 months ago

Another important point the pcd layout and the actual one constructed in step 4 are different to the circuit diagram in step 3 don't go off the crcit diagram

Lets JustB5 months ago

Now i have drilled the holes using a 1mm drill bit

2015-03-30 23.36.37.jpg2015-03-30 23.36.58.jpg2015-03-30 23.37.08.jpg2015-03-30 23.37.25.jpg2015-03-30 23.47.10.jpg2015-03-30 23.48.53.jpg2015-03-30 23.51.04.jpg2015-03-30 23.37.29.jpg2015-03-30 23.51.31.jpg2015-03-31 19.13.26.jpg2015-03-31 18.58.21.jpg2015-03-31 19.44.48.jpg2015-03-31 19.44.41.jpg
Lets JustB5 months ago

I am currently building this project. an easy way to make the circuit board is easy to make if you put it on a pdf. I attached it am made it to scale. I then printed it on press and peel transfer paper and etched it using an eching compound the instructions are on the attached image of how to do that. I bought all of the parts Bayley said to buy.

2015-03-30 23.36.37.jpg2015-03-30 23.36.58.jpg2015-03-30 23.37.08.jpg2015-03-30 23.37.25.jpg2015-03-30 23.47.10.jpg2015-03-30 23.48.53.jpg2015-03-30 23.51.04.jpg2015-03-30 23.37.29.jpg2015-03-30 23.51.31.jpg
crogshockey5 months ago

Great project, can you please send me the schematic drawing.

thanks,

transistor26 months ago

this is really cool, if you had a chance could you upload a basic circuit diagram i want to build a baby version of this to heat nails, any help is greatly appreicated

trancejockey9 months ago

Hi,

I am needing an induction heater to melt stainless for metal casting.

Will this heater melt stainless in a crucible?

hi, what kind of measuring system would you use to measure the current through the coil? i'm working on a induction heater and I don't know the currents and frequencies that pass through the coil, i'm not sure how to measure them since i believe the currents are about 700-1000 A.

Thanks! They're possibly one of the best made containers of any sort.

Thanks! They're possibly one of the best made containers of any sort.

irondwarf1 year ago

do the ferrite cores have to be that large?, I am having difficulty finding any that big here in the UK

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.

http://www.mag-inc.com/company/news/new-4-inch--kool-mu-toroid

chimpera1 year ago

This is the best work I have seen, thanks for sharing. Given the one picture however I wonder if your getting 30kva. Can we see more results somewhere? I understand a much lower frequency would be better for melting, what changes might that require? Thanks, Ben

irondwarf1 year ago

this link will give you a bigger schematic

http://www.instructables.com/file/F20WZQPGQBCHZIY/?size=ORIGINAL

irondwarf1 year ago

have noticed that the photo of the inside of the case the tank coil is multi tapped and there is a toroid by the tank cap that I can see no mention of and the schematic has mosfets whilst the rest of this says IGBTs for stage 2

nahshon1 year ago

I've got a counter top induction range that I'd like to reverse engineer into something like this, can I use the same schemata?

nadrvd1 year ago

I have purchased and assembled all of the components as illustrated. The only thing I am having difficulty with are the two small ferrite inductors. Can you please send me the schematics for these?

Thank you.

Have a look at this:

http://wiki.4hv.org/index.php/Gate_drive_transform...

Good explaination about using a toroid as a gate drive TXer. It's important info about making this instructable since without it you are likely to lose a couple hundred dollars blowing you IGBT if done wrong. I personally think naming specific toroid types would have been proper for "instruction". I would start with something like : FT-150-J. Maybe bigger and fairly thick. That is a ferrite 1.5 inch O.D.

Wrap it tight, place it near the transistors as he has pictured. That is important. In the schematic he has a series resistor in the first gate drive board so you should not have to place one of your own.

You should not have to wrap more that 15 turns to get the proper signal transfer. No less than 9 turns. That is the "grey area". Too many wraps and it's bad. Too few and it's bad. He hints to 10 windings and that is a good starting place. Trial and error here without a scope could be frustrating. If you try it without one, monitor those IGBT and transistors with low bus voltage for a while to see how hot they get. I would use a variac and no more than 40 volts if it sucks less than 10 amps and adjust for max current draw with the inverter. If it can't handle that you will probably have a little explosion at 240 volts.

elricker1 year ago

About the 2 ferrite coils, my 2 cents.

Since these are basically isolation TX's, and from the hints from how bwang comments and the pictures, I believe he is using CAT5 cable which has 5 sets of 2 twisted wires. And that would be better to have each winding twisted tightly so it makes sense since they come that way.

And I would assume that he is using ferrite only and not iron cores that are of the material best made for the frequency they operate. That would be, I think, FT-xx- J or 77 type cores. You probably can not just use any core since some types of materials will actually "choke" signals at certain frequencies. So you should have the right ferrite to begin with.

Now with lack of detailed info I can only offer help to windings. I would assume that they are 1:1, meaning the primary will have the same amount of windings as the secondaries. It could be a bit more or less. It would be nice to know more about how he did it and I wish to have seen that in more detail.

So I would take the 5 pairs of twisted wires from the CAT5 cable and wind them around the toroid coil about 10 times. Choose one of those 5 pairs and put it to the driver, and the other 4 to the transistors as in the schematic. This is where having an oscilloscope would be handy as well as more info because of the trial and error. You are transferring the square wave signal from the drivers to the transistors. The signal needs to be clean. The wrong coil can cause no function to ringing.

I could be wrong and the windings could be a lesser or more ratio. But it would not be much, on order of . 2 in difference. He might have even wound the 4 pairs of wires first then would the primary over them. I don't know.

If you ever read this bwang, please tell us what core materials you ended up using. It appears you at least tried one other coil that did not end up being in your final pic. And info about the windings@!

Hope this helps.

elricker1 year ago

Bwang, Thank you for the great build. After mulling over your project I have a few questions and considerations.

You explain in short many of the aspects to this project but there are a few details that beginners might not be able to understand and are hard to deduce from the text. May I suggest more detail about winding the toroid cores for gate drives. I think it is confusing. I am sure you left it a little vague becuase they are areas where a bit if trial and error are needed to tune it just right and depends on the core itself. And just to be sure you used strictly ferrites and not powder iron ferrites for the gate drive TXs?

Also I think pointing out the use of ferrite for the main coupling transformer. I have seen builds using type 3 iron cores work but they got warm. Toroids are confusing to newer persons that might want to attempt this.

The schematic is useful but I found differences in it and you pics. The potentiometers are interchanged on the schematic from what is shows later. I think it was the 20k and 50k. And it looks like you used a 10 turn for the pot your mounted control. Just to be clear, which one did you mount on the board and which one on the chassis?

Last thing of question would be layout. Have you experienced any funky signals from placement? I see you mounted (glued), yours very close to the chassis. Was that needed becuase you got bad signals?

I hope you can chuck in a comment back to this. I am sure there are many persons who would appreciate it.

Thanks!

akeem22031 year ago

please, can someone tell me how to wind the "gate drive transformers" to get 8 terminals to drive the mosfet and the IGBT.

chimplost1 year ago

Great project, can you please send me the schematic drawing.

Ali Suhail1 year ago
Hi,
Great project, can you please send me the schematic drawing.
thanks,
email - nuggetcreations@gmail.com
shenninger1 year ago
Awesome design. On the final iteration, did you 86 the 4 position rotary switch between the inverter & coupling transformer? I can't find it on some of the pictures or the wiring diagram. Please help me understand!
exenhin1 year ago
thanks
chirume1 year ago
sent me the shematics please
chirume1 year ago
thank you i am interested in this project. can you sent me the schematics.
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