1000w Induction Heater

[Chris SheltonParticipant @chrisshelton11794]

Hi All,

Has anyone any experience of using one of these units for annealing or hardening metals?

Chris

[Chris SheltonParticipant @chrisshelton11794]

[Dave DanielsParticipant @davedaniels93256]

Chris

No, but I did make this:

**LINK**

just for fun about a year ago and it does work.

Video a bit tiresome to listen to, but soldier on.

Your coil seems a bit odd though. Do the turns really touch each other? They shouldn't !

Your device looks a bit similar to this:

https://markobakula.wordpress.com/power-electronics/500w-royer-induction-heater/

which I might have a go at as it avoids the irritating centre-tap …

 

Dave

 

 

 

 

 

Edited By Dave Daniels on 24/11/2015 18:04:26

Edited By Dave Daniels on 24/11/2015 18:16:38

[AjohnwParticipant @ajohnw51620]

That looks like this one. $55 of amazon

**LINK**

John

–

[AjohnwParticipant @ajohnw51620]

It looks to be a bit cheaper off ebay with a world wide search.

John

–

Edited By John W1 on 24/11/2015 21:40:01

[John DeArmondParticipant @johndearmond16553]

Morning Gentlemen,

I'm John DeArmond, Chief Engineer at Fluxeon.com, a company that manufactures induction heaters.

I have one of these heaters. We buy such heaters to do competitive analyses on. It turned out to be what I thought – a knockoff of one of my very earliest open source designs from back when induction heating was a hobby.

It works – sorta. It requires an odd voltage and current that not many folks have around. Something like 50 volts at 20 amps. The reason that the voltage is odd is that it derives gate drive for the FETs directly from the source of the opposite side. By the time the voltage reaches about 50 volts, the dropping resistor to get the gate voltage down to the required 15 volts is high enough that the switching becomes slow enough to overheat and burn out the transistors.

The other main problem is that the coil is at the DC supply voltage. No, the coils do not touch. That is a superbly made work coil, probably the best part of the unit.

That design taught me that I had to separate gate drive from the coil voltage. This is the resulting design.

http://www.neon-john.com/Induction/Roy/Roy.htm

This design separates the switching and the gate drive and prevents simultaneous gate turn-on by using a simple flip-flop. This unit will run from US mains voltage (120). because the voltage appearing across the IGBT collectors is 3X the DC supply, I haven't yet found an affordable transistor to work at 230 volts.

This page is a bit outdated but I'll be doing a revision real soon now Our current main product, the Roy portable induction heater uses this basic architecture. I found a faster transistor so it can run at higher frequencies and my gate driver includes integral desaturation protection and Miller clamping. The next revision of the open source unit will reflect these changes.

Officially our most powerful heater is 3kW. On the bench I have one running at 6kW, the only change being better heat sinking and a larger transformer. I use an output transformer for life safety considerations.

IF you want to experiment with induction heating, the transformer-coupled Royer is the easiest and least expensive way to go.

 

John

 

 

Edited By Neil Wyatt on 25/11/2015 17:13:16

[Neil WyattModerator @neilwyatt]

Welcome John, its appreciated that someone in this for a profession is willing to help amateurs.

I've made your link into a 'live' one.

Neil

[modeng2000Participant @modeng2000]

Very interesting John, thanks for putting it on the forum.

John

[AjohnwParticipant @ajohnw51620]

Thank's John.

I couldn't help ordering one to play with and maybe to have a tamper with it. I concluded that the price is worth the bits and will be interested to see what it can do. I suspect I will be limited to 15v but could provide a lot more current than needed at that voltage. I'm not sure if there is an easy answer to that. Probably not. I did mess with trying to produce my own model aircraft transmitter years ago. Similar problems.

Not sure when induction heating was just a hobby. I saw it being used at Bullpits (AKA Swan kettles and knives etc and also larger military cartridge cases) something like 40 years ago.

John

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[Chris SheltonParticipant @chrisshelton11794]

Thank you all for the replies,

I purchased the heater from a seller called wishyou-happy for £25.79 including P&P , it arrived very quickly, I do not think I could have sourced the parts for any less, and it's ready made.

The coil is as received and might have been squashed in the post, I will space the coils out before using it.

Dave I had already watched the YouTube video before I purchased the heater, and John De Armond I have looked on your website and have made note of your comments regarding a separate gate supply.

I have ordered a 48 volt 10 Amp power supply, but it has not arrived yet.

Would it be worth sliding fiberglass sleeving onto the coil?

I will report on its performance when the supply arrives.

Chris

[John DeArmondParticipant @johndearmond16553]

Posted by Chris Shelton on 25/11/2015 18:59:16:

Would it be worth sliding fiberglass sleeving onto the coil?

I will report on its performance when the supply arrives.

Yes, absolutely sleeve the coil. 48 volts isn't too much of a shock hazard but shorting two adjacent coils together usually ends up smoking the transistors.

John

[Anonymous]

Nice to see a Royer oscillator being used; you don't come across them very often.

Andrew

[Author]

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