# Induction Heater Plans



## lazersteve

All,

Since the weather has not been favorable for refining and filming outdoors here in 'sunny' Florida, I've spent a few days on my upcoming Induction Heating project for melting precious metals.

I located an excellent video on you tube where a gent named Karim demonstrates a do-it-yourself induction heater that *melts steel*.

Induction Heating

I dug around the web a bit and located his hand drawn schematics of the device. 

I ordered all the parts Monday for mine and finished up redrawing his schematics just now. After getting his permission to post a modified version of his project I've decided to share it with the group.

Schematics

This project is very straight forward and requires only two specialized parts. I'll be posting my progress on my site and linking to the project videos here.

I've ordered extra parts for those that may be interested in building one. I estimate the total cost of the project components is less than $500.

Steve


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## Noxx

This interests me a lot...

Thanks for the great inputs. 

And keep the infos comings ! 8)


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## Noxx

And could you tell the parts needed ? I want to know what I'll need to buy to estimate the cost.

Thanks


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## Platdigger

This is over the top Steve!
Been looking for something like this for a long time.....as I am sure many have.
Randy


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## lazersteve

Randy,

I've been hunting the internet for this exact device. Small, easy to build, simple design, and powerful (3KW +).

The guy who designed it said with a few minor mods it can reach 10KW!

I want to melt my gold and other PMs in a few seconds without any flame. 8) 

I've got some more ideas for it also. 

Here's an outline of my plans:

Step 1. Gather the parts.

Step 2. Build the rig.

Step 3. Post the videos.

Step 4. Integrate the device into my refining routines.

Two boxes of parts arrived at my door today. 

I should have all my components by this time next week if all goes well. :wink: 

Stay tuned I'll keep this thread updated with more news.

Steve


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## Platdigger

Beautiful..!....
Randy


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## jimdoc

Steve,
Thanks for sharing this with us. I also
have been looking into a project like 
this, ever since I saw this link;

http://www.scienceinafrica.co.za/2003/november/toaster.htm

Jim


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## lazersteve

Jim,

I saw that one several months ago also. I noticed they used a couple of Microwave oven transformers in the design. 

When my mine is finished, it should weigh about half as much.  


Steve


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## lazersteve

All,

If you downloaded the schematics prior to this post (1/25/08 8:33 CST), please download the updated version and repalce the old version.

The latest version has a different L2 coil arrangement and a few modifications to the coils.


I'm working out the coil details of the print with the designer and it may change again so keep an eye on this thread if you are interested. 

Sorry for the changes, my website will always have the latest versions available.

Steve


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## banjags

So what do you figure in the end this furnace is going to cost you to build?


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## Gotrek

I use a waste oil fired furnace to melt my metals (aluminum, brass, bronze my refractory isn't adequate for temps needed to melt steel but I have been able to do it in he past (sacrificing the refractory))

How much power will this furnace use, waste oil is pretty much a free fuel for me. Do you ahve an estimate on cost of running. I'm sorry if it's answered in the video's I'm unable to wath them. Building a flameless furnace has been on my mind for a while since the neighbours started complaining..


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## lazersteve

Jason said:


> So what do you figure in the end this furnace is going to cost you to build?



Jason,

I just got the quote on the last parts this morning, looks like around $375 to buy everything needed.

Gotrek,

Welcome to the forum,

The operational costs of the furnace will be low compared to a conventional electric furnace due to the accelerated heating rate of induction furnaces. 

The average cost per kilowatt hour in the US as of March 2006 was 9.86 cents per kWh. The unit described draws 3kW per hour of operation, or 29.58 cents per hour to operate (slightly more at todays kWh prices). At 3kW the unit can melt a hardened steel socket in less than 60 seconds.

Steve


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## Gotrek

Very interesting definately keep us posted.


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## Noxx

Any ways to get the parts list lol ? :lol:


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## Noxx

I don't know much about induction heating but I suppose you need a PLL driver and an H-bridge ?


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## jimdoc

Noxx,
The parts list is on page 2 of the schematics.
Or do you mean more detailed with where to
get the parts? Jim


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## Noxx

Poor me, I didn't see the second page of the schematic...

Sorry...

(Thanks Jim)


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## Gotrek

I didn't either until just now. I have some of those parts already, some of the semionductors and transformers I* bet most people here have 1/4 of those parts already.


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## Anonymous

wonder what he was trying to use as a crucible? that falure was kinda interesting.

Jim


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## Noxx

I don't know... It looks like Plaster of Paris


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## aflacglobal

Good job Steve. 

:wink:


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## Anonymous

Has anyone used an arc furnace? From what I have read they are easy to build and will melt anything. I even read in an old science experiment book of building one with the carbon rods from batteries, suitable fire brick, and a 100 w light bulb to controls the amp draw. That seemed real easy to build as it was for 9th graders.

Jim


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## aflacglobal

http://www.jackroeusa.com/Cinema-carbons.html


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## Lou

http://sciencemadness.org/talk/viewthread.php?tid=9793

is an arc furnace.

Theo Gray has a nice one he made as well.
see www.theodoregray.com



My friend Tim has also built his own induction furnace which works.

Video is available on his website:

http://webpages.charter.net/dawill/tmoranwms/Elec_IndHeat7.html


I look forward to hearing your results Steve!!


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## Noxx

I'm not able to locate any of the Inductors and Transformers parts.
Where can I get them ?

Thanks

Oh and I can't wait to see your setup :lol:


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## lazersteve

Noxx,

A couple of the inductors are homemade. I'll can show you how they are made.

The work coil (L1) is merely 4 turns of 1/4 - 3/8" copper tubing.

The matching coil (L2) is a bifilar wound coil of 7 turns of 10 AWG insulated wire on a flat spool air core form.

The feedback coil (L3) is 50 turns of insulated 14 AWG stranded wire wrapped on 1/2 of an old flyback core (C-Core) and hung from the work coil hot side via a 1/4 copper braid the ends of which are soldered to the work coil spaced at 1". The feedback coil gets zip tied to the resistive divider (braid) to provide feedback coupling from the work coil.

The 1:500 current transformer (T1) is a store bought item. I'm waiting on mine to arrive. I bought 10 of them if you need one we can work something out.

The 12 Vac 1 A supply transform is a standard Radio shack part as listed in the parts list.

As my unit takes shape I'll be posting photos.

Steve


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## Noxx

Ok thanks for the precisions...

I found the radioshack part... The part # is 273-1352

Don't add the letter «A» as stated in the schema.


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## Noxx

I've got an idea.

One could use Kaowool (or similar) to isolate the heat generated by the metal in fusion. This way, the copper pipe will not get that hot (a way from melting point), the heating will be faster and the melted metal will stay hot for much longer.

That's just my two cents.

And, is it possible to use a graphite crucible in this setup ?

Thanks


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## Platdigger

Graphite yes.
The copper tubing is water cooled. But the insulation couldn't hurt.


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## Anonymous

I think the copper may be getting hot from the amperage it is carrying and since it does not have a counter to self inductance. 

Jim


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## Lou

Ah, it seems you did not watch that video my friend made of his induction furnace. It is lined with kaowool that I provided to him. You need kaowool if you want to melt and hold metals as a liquid.

Graphite crucibles work well.


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## lazersteve

All,

I finished the overall construction of the power and driver circuits today. I'm waiting on the 200 Kvar capacitors and a few more components for the work coil assembly. When they arrive I'll complete the unit and run some melting tests.

Here's the way the cabinet looks right now:

[img:538:1828]http://www.goldrecovery.us/images/induction_overall.jpg[/img]

Be sure to click on the image to see the closeup view.

Steve


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## Noxx

That's great (you did it fast too)
Do you think this won't generate too much heat ?


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## Anonymous

Steve you are very talented.

Jim


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## lazersteve

Noxx,

I plan on routing the copper tubing carrying the water over the heat sinks and attaching it with some copper clamps to keep the transistors cool. Everything else (the low voltage stuff) shouldn't generate much, if any heat.

I'm also planning on a few well placed miniature fans. Remember the rig you see in the photo is not completed.

Steve


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## Irons

james122964 said:


> I think the copper may be getting hot from the amperage it is carrying and since it does not have a counter to self inductance.
> 
> Jim



Ohm's Law strikes again. There are also eddy currents in the copper that generate heat. RF doesn't behave as nicely as DC. Then there is radiant heating from the melting metal in the crucible.

There's always using Silver tubing . A heavy Silver plate might help .8)


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## Platdigger

Irons, they use copper for this ....all the time. It is the "only" thing I have ever heard of being used for indution heating in fact.
Randy


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## Absolutsecurity

NICE WORK Steve!!!!!!!!

That looks like some top notch work! 

Would you have any interest in making a working unit or kit for sale?

Just a thought - I know I would be interested and others might be as well!

A kit would be nice - then all the parts would be there and it would just be like the 1000 other projects that I cant get time to complete around here!! LOL!

Glynn


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## Irons

Platdigger said:


> Irons, they use copper for this ....all the time. It is the "only" thing I have ever heard of being used for indution heating in fact.
> Randy



No doubt copper is used. I just brought up Silver because it has a lower resistance than Copper.

If they were both the same cost, silver might be a better choice. It would make a more efficient tank circuit. The choice in capacitors would also make a difference.


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## lazersteve

Irons,

The tank caps are the most expensive part of this project. I got two of them shipped for a cool $249.

Steve


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## Platdigger

I am sure I can get all the parts together. Now, if I can just get someone to put it together for me....yea.

I am a pretty good welder, but never was much for soldering. Perhaps if I just got someone to put the circut board together.


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## lazersteve

All,

I've ordered enough parts to build at least 10 of the low voltage circuit boards. If anyone wants one built let me know I'll get a price and post them on my website.

Steve


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## Lou

I'd be interested in buying a complete unit or kit after I see a video of you melting Pd or Pt with it.


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## aflacglobal

Lou said:


> I'd be interested in buying a complete unit or kit after I see a video of you melting Pd or Pt with it.



:lol: skeptics :lol:


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## Absolutsecurity

I would be interested in a complete unit also Steve or a kit with all the pieces there so I can sit down with my boy and build it together like a HeathKit type deal - I just know I dont have the time to go looking for all the pieces but I could buy complete or buy a kit to build!

Let me know Steve - I am very interested!

PS. The balls are coming along nicely - all the silver is complete just have to start on the gold now. Started some gold balls in 50/50 nitric - just think I have to heat the dilute nitric on the gold balls - sitting cold im just getting a little blue solution (too cold here for the acid to react).

Glynn


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## lazersteve

Ralph,

It's really a big challenge. 

The unit in the original video operates at around 3.1 kW output power. The author of that video said I should be able to get 10kW out of the unit off of US mains due to the higher amps we have here (?) in our line circuits. 

If the 3.1 kW unit reaches temperature enough to melt vanadium-steel alloy the 10 kW unit should be able to melt Pd and Pt (I'm hoping). It will definitely be interesting to try.

Gold, silver, and even copper should be a walk in the park for the rig even at 3.1 kW.

Steve


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## Anonymous

More KW should allow you to melt a larger volume not sure it would affect the ultimate temperature reached. 10 kw = 34000 or so btu/hr the specific heat of the objected to be melted would determine the temperature you would reach in 1 hour, though I doubt you would let it run that long.

Jim


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## aflacglobal

Oh, you don't have to tell me i know the difficulties involved.

I was thinking legal liability issue a little while ago. If you sell the assembled unit you will be labile, but if you sell the kit at least you will have some distance from that issue. As far as i know a kit could be almost pre fabed with very little assembly required by the buyer just as long as it's not sold as a ready made product. Call it for educational purposes only.

Just a thought.


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## Absolutsecurity

Thats cool I will take a kit then! Steve can you please come up with a kit - I allready have the excuse for my wife! My son and I can make it together! LOL! PLEASE!   

Glynn


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## Irons

I probably have a lot of the parts on hand but I know what a pain it is to find parts that work correctly and tweak them.

My sig says it all.

Do you think a 220V model would be better? Many folks have a 220V service connection for an electric stove which would be more appropriate for this level of power usage.

There's always some peckerwood who will try to run it on a cheap 110V extension cord and burn their house down.


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## lazersteve

Irons, 

The unit requires 220 Vac input.


Steve


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## Gotrek

I'm interested in a kit as well if ever one is available.


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## lazersteve

All,

I've completed the work coil today. 

Here's a photo:

[img:536:1114]http://www.goldrecovery.us/images/work_coil.jpg[/img]


It's made of 1/4" ID (3/8" OD) soft copper tubing. I've added some brass couplings to allow the coil to be swapped out at a later date if desired to suit suit various work pieces.

I also received the T1 500:1 current transformers today that I had ordered. I have plenty of them if anyone is interested. 

I'm working on a quick etch pattern for the inverter/ IGBT driver board. I plan on etching them using an industrial CO2 laser that I have access to. I've never etched a PCB with the laser so it should prove to be interesting. If the laser test works I'll be able to produce the boards as they are needed. If not I'll have to go with an AP etch bath instead. The CO2 laser is already in production using AutoCad DXF files to carve tool kit foam so I'm working on a DXF of the circuit layout to drive the laser. The laser is more than capable of cutting metal so the copper clad layer on the PCB's should not pose a real problem.

I'm still waiting on my Celem capacitors (C1 & C2) to arrive from Israel. They are due to show around the end of February. I plan on having the remainder of the project assembled by the time they arrive.

Steve


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## Harold_V

You can be proud of the job you did on the coil, Steve. Looks very professional.


Harold


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## lazersteve

Thank you Harold.

It nearly killed me to bend the thing. I used one of those cheap spring style coil benders. It worked, but it's really hard on the hands.

Years ago I used to work in an assembly plant where we built controller cabinets from blueprints and a bunch of raw materials. We had to build everything from scratch. Some of the cabinets called for copper tubing to be routed throughout the assembly. I learned everything I know about bending copper at that job. We used the fancy swing arm benders to do the tubing back then. I'm not sure I could have made the loops as well using the swing arm bender.

Steve


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## Absolutsecurity

Wow nice looking coil Steve!!!!!!

I am very interested in a kit if and when you get one together! PLEASE let me know and reserve one for me!

I sent you a PM earlier.

Glynn


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## Harold_V

lazersteve said:


> I'm not sure I could have made the loops as well using the swing arm bender.
> 
> Steve



In my opinion, the only way you could have come close to duplicating your success would to have wound the coil on a form that had the proper diameter grooves machined, along with the proper lead. I studied the coil for quite a while. I'm truly impressed. It shows you know more than nothing about forming tubing. 

Harold


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## Anonymous

I agree with Harold you did an excellent job on that coil. You would do well in refrigeration repair.

Jim


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## Froggy

I have had to bend stainless steel tubing, pack it with sand first and it sure helps from flattening out, figure this woud make copper real easy. lokks great steve,


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## Anonymous

lazersteve what is the maximum temperature potential of your induction heater.


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## lazersteve

The max temperature remains to be seen. 

Steve


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## Platdigger

I don't believe there is really a limit to the temperature that can be obtained with this process. 
That is, until you reach a point were you don't have sufficient power to overcome the heat losses, the stuff you are melting vaporizes, or you reach the limit of your container.
I mean, you can melt just about any metal with one of these.
Randy


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## Harold_V

Platdigger said:


> I don't believe there is really a limit to the temperature that can be obtained with this process. Randy



Typically, you're limited by the refractory and handling equipment. 

Harold


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## peter i

We have a couple of induktion furnaces at the department of chemistry (used for growing crystals). They will melt a tungsten rod when asked to :wink: 

At high temperatures, heat is lost rapidly by radiation, and the moment you lose the same amount of heat as you pour in, the temperature will reach a steady state.

(And a very nice coil!)


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## Gotrek

Wow what a great job I can't wai to see it in action.


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## Froggy

Where are you at on this steve?


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## lazersteve

Frog,

I have secured all the parts for the unit, but I haven't finished the assembly phase. After assembly will be set up and testing. 

A friend of mine had the opportunity to test some Platinum in several induction heaters and did not have good results. He tried melting 150+ grams in a variety of manufactured induction heaters from low frequency types to higher frequency types (3kW-15kW). He was only able to achieve slight surface melting. 

It's worth noting he did not have access to any refractory materials to prevent the convection of heat away from the test material. It may be that the refractory is a requirement for melting. I'm sure it would help.

Since his tests, I decided to buy a hydrogen torch to complete my Pt DVD. I'm finalizing the edits on my Pt DVD and should have it completed soon.

Yesterday I found some more information on dissolving Pt that should be useful on cats if the information I have found proves to be true. Considering the source of the material, I'm certain of it's accuracy, but skeptical on the proper conditions listed in the manual.

Steve


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## Froggy

I was chatting with the gal at http://www.inductiontech.com/page12.shtml and she coulndt express enough how important the power supply was,, for pt etc. it needs to be 10,000 cycles...40kw? Wonder what kind of crucible your friend was using? I have been invited up to North Texas Refinery to try out cat material in a commercial induction heater made by the company above, the guy who owns the place said I had free access to his equipment,lab, and his staff!! He has been thinking of doing something with converters and would be more than willing to help me, obviously he wants me to help him.. I also contacted a company in Cali.---Kinburski bros.-- about melting cats in induction furnaces, no one was there except the sec. and the lab guy, what luck, the lab guy rattled on with all kinds of useful info, they do use induction heaters for recovery of metals in Cats, said it was simple and that the flux has to be really soupy. I will be travelling to N.T Refinery this week and will take pics, wish me luck. Frog


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## Harold_V

Froggy said:


> I was chatting with the gal at http://www.inductiontech.com/page12.shtml and she coulndt express enough how important the power supply was,, for pt etc. it needs to be 10,000 cycles...40kw?



You need to talk to someone else. 

As an induction furnace owner, assuming you intend to melt metals, I know that the frequency and power are related to the size of the charge in question, and nothing else. If you are heating metallic substances, it makes no difference if they be platinum or iron. It's the size of the charge that dictates frequency. If you desire to melt a half ounce of platinum, the frequency must by much higher than for melting 50 pounds. Power is a function of speed, although you must have enough power to yield the desired results. Greater power simply shortens the time to melting. 

Non metallic substances can be heated equally as well, although higher frequencies are required. Think microwave oven. 

Harold


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## Palladium

Harold_V said:


> If you are heating metallic substances, it makes no difference if they be platinum or iron.  It's the size of the charge that dictates frequency.  If you desire to melt a half ounce of platinum, the frequency must by much higher than for melting 50 pounds. Power is a function of speed, although you must have enough power to yield the desired results. Greater power simply shortens the time to melting. Harold



Not only is it the size of the charge, It's also the density of the material involved. Frequencies will penetrate different metals at different depths because of the frequency.


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## Palladium

lazersteve said:


> A friend of mine had the opportunity to test some Platinum in several induction heaters and did not have good results. He tried melting 150+ grams in a variety of manufactured induction heaters from low frequency types to higher frequency types (3kW-15kW). He was only able to achieve slight surface melting. Steve




Huummmm. Should have worked. Check this out steve. Note the numbers. :wink: http://www.scienceinafrica.co.za/2003/november/toaster.htm


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## Froggy

So Harold your saying the old cliche' "size matters"?  I didnt go into details about our conversation but, She said the same things you are saying..... The nice thing thing that came out of our conversation was the redirection she sent me. ie... why bother trying to build one or buy one when you can use someone elses for testing or production (at the capacity I want to do). Like I said earlier, this week I will be with a few lab techs. at this refinery and they can help out, I'm just bringing my limited knoweledge about cats to the table... Actually, looking at my notes it was a guy in Fla. that said 10,000 cycle for pgm's , then he went on a tirade about alot of stuff, after listening to him I thanked him and went about my way(Marvin-Republic metals )....


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## Harold_V

Palladium said:


> Not only is it the size of the charge, It's also the density of the material involved. Frequencies will penetrate different metals at different depths because of the frequency.



That's correct. If you start with chips (waste material from machining processes), an induction furnace may not be able to melt them directly without starting with a larger mass of material. Higher frequency can avoid the problem, but may be too high for heating a given volume once it is molten. As the volume of melted material changes, so to do the characteristics of the furnace. Older furnaces, such as the one I own (motor generator type), have a series of water cooled capacitors that can be constantly switched to compensate for power factor. It changes as solids are liquefied. 

The latest generation of induction furnaces (solid state) compensate by other means. 

Harold


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## Harold_V

Froggy said:


> why bother trying to build one or buy one when you can use someone elses for testing or production (at the capacity I want to do).


At the risk of offending, I can't imagine anyone without a considerable background in electronics and some serious machine tools at their disposal being able to build an induction furnace of any size that would be useful for anything besides lab work. 

The power involved is immense (mine requires a 400 amp service, three phase, and it's a small furnace in the scheme of things), as are the components. One is not likely to build anything that serves a purpose of processing cats in volume. Even then, the same problems must be overcome. Dissolving (or melting) the constituents of catalytic converters will present problems for the lining of an induction furnace. That is not to be taken lightly. If your lining fails, you short the coil----and destroy the furnace power supply. Induction furnaces are expensive, and have the potential to be dangerous. They should be respected. 

Harold

edit: added missing word


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## Froggy

No offence, I plainly lay my ignorance out for all to see in this field, thats why I am going to a company that has 3 induction furnaces and a full lab with techs.... I wish I had spent months on this proccess rather than the chemical methods, but I still enjoyed all the information i have picked up....


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## jimwig

hey there lz.....

you left out one thing on your list ---- make it work.........

this is what i have come up with so far......

http://www.dansworkshop.com/Induction%20Heating.shtml
http://www.richieburnett.co.uk/indheat.html
http://www.ameritherm.com/
http://www.rdoent.com/induction-generator.htm
http://www.ameritherm.com/aboutinduction.php
http://www.popsci.com/diy/article/2003-09/smelting-microwave

some of these are not directly about induction - the last one is more like microwave melting....... that's not melting your microwave.

but there is one that is llike really recent and good. can't put my finger on it but i will.

hope this some kind of help


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## Anonymous

Dear Steve, 
What you have done is outstanding, 
I would also be interested in obtaining a kit, if ever is available.

However I have some questions. If we follow the resonant frequency of 125kHz and use the formula to compute the inductance of a coil

Inductance = D*D*n*n/(18*D+40*l)
where 'D' is the outside diamenter in inches, 'n' is the number of turns and 'l' is the length of the coil in inches, and plug the values for D=4 inches, n = 4 and l=4 inches, 

I obtain for inductance 1.1034 uH

using the resonant frequency formula 2*pi*f = 1/sqrt(LC) 
and solving for C, the matching capacitor would be 1.46uF

My question is, wouldn't it be better to have larger inductor so the size of the capacitor would be smaller?

for example, lets say 8 turns --> L=4.41uH --> C = 0.367 uF

Great work.
Ram


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## scwiers

newbie q:
now that I got my WVO furnace all tuned up, induction is already my next want. And if I had a clue as to how to read schematics and do electrical testing, I'd be raiding some junked microwave ovens in my garage in a flash. Or hold out for Steve's kit.

Seriously though, I'm wondering how induction might help out melting my alloys on a small scale. Right now, pretty much I'm reducing chlorides that I get from liquor. Mostly Cu, with trace PMs. I gather that reducing oxides/chlorides etc. by induction is a no-no, right?

Still, once I get the reduced metal, if I could guarantee that a 1 kg melt, say, was at least 50-75% Cu, for inquartation purposes, I'm wondering if induction could be the key.

And as everyone else has already said, great coil, Steve.


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## lazersteve

Ram,

The capacitor provides the necessary power for the coil circuit in the form of charge or Q (coulombs).

The formula for Q is Q=C * E where C is the capacitance and E is the voltage.

The power formula is Q= a * t where a= amps and t = time.

A larger capacitor equals more charge which in turn will produce more power in a shorter time.

Aside from that observation, I didn't design the circuit or the component values, Kim Ladha did.

Steve


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## kjavanb123

Hi Steve,

So what happened to this project?

Regards
Kevin


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## lazersteve

The project had to be put on hold for work. 

When I left my government day job to refine full time, my free time and money flow both became dependent upon the amount of time spent in the lab. Since the bills don't pay themselves, I had to shelve several back burner projects and concentrate on feeding the family and keeping up with the ever increasing insurance, food, and shelter costs.

Steve


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