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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

Picture of 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.

 
chiranth17 days ago

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?

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.

BenderSanchez2 months ago

Noah nice :D

engineerings3 months ago

HELLO .. I LIKE IT VERY MUCH AND NEED SOME HELP WITH Coupling transformer CONNECTION
PLEASE TELL ME WHERE CAN I FIX THE 2 WIRE FOR Coupling transformer ?

engineerings3 months ago
rswain33 months ago

Any way I could get a parts list? I would love to make one of the 3k ones

mrandle5 months ago
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.
overbusy5 months ago

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 ?
Thanks.

imsmooth (author)  overbusy5 months ago
The h-bridge adds more mosfets and cost without any great benefit.

If you go to my website you'll see why the 0.22uf caps are needed.

Go to inductionheatertutorial.com
overbusy imsmooth5 months ago

You are right, but often mosfets can cost less than good quality snubbers/capacitors. Anyway it was only an idea.

...Ok, I understand that 0.22 caps are needed for a sine wave "production"; but is the cap on the secondary (in series with the work coil) really needed ?

Thanks.

sina majidi9 months ago

hi

thanks for your article

the schematic picture isn't clear

i can't find details on the schematic

please send me your schematic,it's very emergency :D

at last i wish secsusfully for you

mail:sin.majidi@Gmail.com

trinijay1 year ago

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,

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

For credibility this is my website, http://skydom.weebly.com/creators--partners.html and I'm making this on behalf of a makerspace i am with.


the sketch for the arduino programming is all I really need

bpark10001 year ago

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" wide 3" diameter), then through the work coil. So there was no voltage applied to the water, other then a small resistive component.

imsmooth (author)  bpark10001 year ago
There are no dissimilar metals
Only copper

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?)

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).

High-power lasers had this and the water was carefully deionized, but it corrodes anyway.
WillowFox1 year ago

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.

pollux641 year ago

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.

Nevala1 year ago

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.
I would recommend getting some inexpensive firebrick for collecting the metal ejection.

Wow this give a person the insight on how the inverter welding machines work! They are light and give excellent resuls

Wow this give a person the insight on how the inverter welding machines work! They are light and give excellent resuls

Jackn71 year ago

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.

Do you have to use distilled water or anything?

imsmooth (author)  Jackn71 year ago

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.

Thanks for taking the time to answer. :)

Yeah I was thinking about possible conductivity issues, or changes in inductance, that sort of thing.

Separate cooling for the Mosfets and the working coil makes sense too.

Cheers!

how much does this cost to make

imsmooth (author)  transistor21 year ago

3kw is about $300

12kw is about $1000

fzumrk1 year ago

That thing is scary! Awesome job.

hzxasdf1 year ago

制作步骤再详细一些

fgeneral1 year ago

nice pro