30 kVA Induction Heater

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.

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.

Step 1: Bill of Materials

For this build, you will need:

• 2 IGBT half-bridge modules. I used Powerex CM400DU-12F 400A 600V Dual IGBTs; anything of similar power handling and switching speed should work. These can be purchased as cheap surplus from Ebay.
• 4 MOSFETs or IGBTs for the gate drive. I used HGTG30N60B3D's, which are way overkill for the application. They need to be able to dissipate about 30W without burning up.
• 2 gate drive IC's, of at least 9A peak current capability. I use the UCC37322 from TI.
• 2 ferrite toroids. These are your gate drive transformers, and should be able to pass a reasonably clean square wave at 50 kHz. Magnetics, Inc. and TSC Ferrite International are good manufacturers, or you can salvage them from old CRTs or switching power supplies. The powered iron cores from ATX supplies rarely work.
• Large ferrite toroids for the toroidial coupling transfromer.
• 1 TL494 PWM IC.
• 1 at least 20 uF, at least 20V film or ceramic capacitor.
• Assorted resistors, capacitors, and potentiometers for the driver.
• 10' of 1/4" soft copper refrigeration tubing.
• A water block capable of accommodating the two IGBTs. A large heatsink may also work, but I haven't tried.
• 2 aluminum or copper bars, ~3/4"x8"
• 2 1/4" compression unions
• A 4-position rotary contactor, good for several tens of amps.
• A screw-terminal electrolytic capacitor of reasonable quality. I recommend at least a few hundred uF for 3-phase operation.
• A high-quality, low inductance snubber capacitor for the bridge. Ebay has cute brick-mount 20 uF blocks for $5.
• One or more high-quality polypropylene capacitors for the tank capacitor. More on this part later.
• An analog current meter good for several tens of amps.
• A 3-phase bridge rectifier (or single-phase if you are willing to settle for single-phase operation only).
• A suitable project case and associated hardware (3-phase breaker, cord, plug, etc).
• A water pump capable of a couple GPM
• Tubing appropriate for hooking up the water-cooling.
• A Variac for testing.

Comments

[msmith136]

Would this design be capable of forging metals with a high melting point, i.e. Iron around 1510 degrees C (2750°F). Or steel at around 1370 degrees C (2500°F)? I'm sweating just thinking about the idea....

[lunuwaththa]

Hello Friend
Can you please upload a clear wiring diagram for this circuits. i am beginner to this field
if you inform me about this cause I will be thankful to you
my email
[e-mail]

[roberlender]

i saw this and its looks very intersting.
i can use it in one of my projects,
i need your help to build it (i have no experiance in electronics)
i have no problem to pay thru paypal and pick it up
i need it asap.
if someine can help me please contact me
[e-mail]
thank you

[John4890]

Is there any chance of you making a video of how to put one of these things together? I have a basic understanding of electronics, but this is a little too advanced to know what I'm doing just by reading.

[patryxpz]

Why didn't you use a tank cap on the primary side of the power transformer? First, on the primary side you have smaller current and voltage that on the secondary, so you can use cap with lower nominal voltage and current (smaller cost of cap). Second, with cap on primary side, resonance frequency of tank not depend so much on melting material.
Waiting for replay.

[bwang]

It doesn't matter, since either way the tank cap needs to handle the same amount of reactive power. On the primary side, the current drops, but the voltage increases (since everything is being reflected through the 1:N "reverse" transformer).

[patryxpz]

You are right. But I think that the most critical parameter in this app is current of cap. if it's to large then cap starts overheats, decresing nominal capacity ( incresing tank resonance) and in final it's crash. On primary side you have lower currnet so the problem is smaller. The voltage of cap is not so big problem, its no problem to find snubber cap at 1200V nominal.

[bwang]

It is infinitely easier to find a capacitor that can handle high currents at low voltages than high currents at high voltages, since series'd caps increase ESR (losses) and decrease capacitance.

[patryxpz]

OK. And what about primary wirring?
I see that it is simple wire without water colling and i'am sure that it will be overheat and isolation will be melt.
I'm suggesting also to test this induction heater for longer time period (1hour for example).
(sorry for my bad english :)

[bwang]

Its been run for 1 hour+ and the primary wiring has yet to melt.

[patryxpz]

Did you measure current (clamp probe) and voltage on secondary side? I'm interesting of secondary current, capacitor voltage and inductor voltage at maximum power (10..30kvA). I'm suspecting that the capacitor is overload - too high current than nominal.

[bwang]

Capacitor current limits are largely thermal, and with water cooling, the capacitor never gets warm.

[hendriono]

Thanks.. I will try before comments...

[2bytes]

Impressively simple and high output design! Wouldn't expect any less from you though. :)

Few questions:
1.) What material type are the coupling transformer toroids?
2.) How much heat if any do the four coupling toroids generate after a decent length high power run, say 2-3 min heating a largish work piece?
3.) With the same run conditions as above do the inverter output wires to the coupling tx and the rotary contacts get hot/warm using what appears to be 14AWG(red) & 12AWG(white) THHN?

[Mirage_662]

HaHa add a secondary coil and you have yourself a monster DRSSTC!

[The nerdling]

can you do this with that?

[The nerdling]

oops didn't work, heres a link http://senorgif.memebase.com/2012/04/30/funny-gifs-what-is-this-sorcery/

[asooy]

with the IGBT's what are you using to water cool it and what are the temps its running at? say i had a skm400gb125D it would be like 150c just from the switching at 65kh.

[bwang]

The inverter is soft-switched, so switching losses are negligible.
I used a CM400DU-12F.

[asooy]

UCC27322 could i replace it with IXDD414YI

[bwang]

Yes

[asooy]

k im just trying to use parts i can get from work

[asooy]

would
FF200R12KE3
http://www.scut-co.com/maindoc/techtrade/pdevice/eupec/documents/datasheets/igbt3/FF200R12KE3.pdf
or
CM200DY-24NF http://www.platan.ru/pdf/1dist/mitsubishi/CM200DY-24NF.pdf
igbt work from what i could see i think they should.

[bwang]

yes.

[asooy]

With the igbt/mosfet is Q1-Q4 mos fetes between the igbt's, and is there a better picture of the hook up between them.

[asooy]

The Thick black line to 4 is that the transformer hooking to Q1-Q4 which i think are the MOSFETs then they hook to another transformer then to both IGBT's Q5-Q8

[bwang]

Can you clarify your question?

[asooy]

The Thick black line to 4 is that the transformer hooking to Q1-Q4 which i think are the MOSFETs then they hook to another transformer then to both IGBT's Q5-Q8

[asooy]

for the tank capacitor what is the voltage and amps, is this a 2uF or 20uF

[bwang]

3.75 uF

[asooy]

how many amps/volts does it need to take, for the input cap what is its uF,amp,volts

[bwang]

The tank cap is a 580Vrms 152Arms poly cap.
My input cap was for 3-phase, so it is only a few hundred uF. Size your own capacitor for single-phase operation.

[asooy]

the input cap would that be c9

[chrwei]

I helped with a custom CNC induction heat treat scanner at work (I did the software) and if you are going to heat treat or need to quench don't use plain water. There's a quench additive that makes the water "sticky" so it won't sputter and takes more heat to boil, using the additive takes a lot of risk out of quenching, makes it "safe". Also putting a pump in the quench tank so the water is moving around will help a lot.

The scanner we have is large and can turn 1144 steel white hot in under a minute, we can run the part through at about 1" per second tops and it's still too slow for full power. It's amazing how powerful induction can be!

This is quite an awesome DIY version, nice job!

[steveastrouk]

Just use plain water, and stir it around HARD as it cools, which prevents the sputtering problem. Special additives are nice,maybe, but not strictly necessary for the home shop

[aphyllophorales]

quenching in brine helps, and circulated brine helps more. Depending on how fast you need to quench, oils may also be an option. Overall, you will get some amount of sputtering, but you should also be protected as a standard measure. At the temperatures we are talking about, a 2nd or 3rd degree is a 'good' resolution to unintended contact.

[wireb]

Another question did you make that water block you used for the IGBTs?
If not where did you find it? Debating if I build my own or not.

[bwang]

I just had it sitting around.

[Nyxius]

Cool ible dude. I might have to rip some of your circuits for my research project. Trying to build a home made Vasimr rocket. Then I will modify it to be air breathing. No good power sources for it to be portable, but fuel cells look promising.

[bwang]

Out of curiosity, what does an induction heater have to do with fuel cells?