My Induction Heating Projects

[T3sl4co1l]

I'm one of the "original" guys that was working on induction heating, around the mid to late 2000s.  An early, nearly complete design:
https://www.seventransistorlabs.com/tmoranwms/Elec_IndHeat6.html
(I should go through these and fix the YT embeds -- the vids are still up there, though I think they've decayed in quality as YT's re-encoded them over the years...)

https://www.seventransistorlabs.com/Images/Induction1104.jpg
The first complete 1kW induction heater kit, that I'm aware of.  I wrote plans for this, though they need some fixing up nowadays and I haven't gotten around to that yet.

https://www.seventransistorlabs.com/Images/Induction1201.jpg
And my 10kW prototype, which I had tested up to 5kW.  Then other activities took priority and I didn't have time to continue development.

Which led to...
https://www.seventransistorlabs.com/Images/Tallboy_HotStuff.jpg
I designed 5kW MOSFET modules, controls and all that, basically the whole system design for a brand new industrial series.  Pictured here is 30kW from six modules strung together.  The series spanned 5 to 50kW and 20 to 400kHz.  I also began work on updating the larger (floor standing) units, which were IGBT powered and spanned 3-50kHz and 150kW per module (stack as many as you like, though I think the largest assembled there was under 1MW).

Since then, I've been doing more general design work; my designs are in production from automotive to medical.  I pride myself on passing EMC within the first prototype.

Tim

[Mads Barnkob]

Welcome to the forum Tim!

That is quite a impressive line of induction heating development, however there is only the proposal of the 1kW IH on your website, did you just not write the documentation yet or can it not be disclosed due to commercial interests?

I have not yet built LCLR induction heaters, but a transformer coupled one is for sure on my list of projects to complete... some day

I looked at the iRadyne website, but could not find much detailed information.

Have you seen the IH capacitors I have for sale? If not you, do you know anyone that could be interested?

[T3sl4co1l]

I've got ideas for a basic 1kW low frequency (20-80kHz) unit, and a fancy, high frequency (500-2000kHz), easy to use unit.  The LF design would be easy enough expandable to 10kW+, with some worthwhile design improvements made.  They're on the back burner right now, in various stages of development.

This in fact is one part of the HF design: demonstrating a constant current buck supply, with a squarewave setpoint and highly nonlinear load.

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And yes, you can see it's been "back burner" for a while...

Tim

[Anders Mikkelsen]

Excellent work, your old website is still the only good and complete induction heater design on the web, with the proper protections. I'm very interested in hearing more about your two concept designs, what power control methods are you going for (detuning, phase shifting, DC bus regulation etc.)? What matching circuit are you using for the tank circuit?

[T3sl4co1l]

Hi,

I used frequency shift (detuning), with PLL to prevent dropping below resonance, and feedback on inverter current and tank voltage to regulate the output as needed.  Gate drives always with desat detection, except for the 1kW kit which is simple enough not to bother (but, accordingly, is subject to failures if the current feedback doesn't act fast enough, or a component or wiring fault occurs that bypasses the current transformer).

I stopped development when I designed an industrial power supply, which was generally the same scheme, but with digital controls (it didn't need it, alas, I was under orders to use an FPGA and 80MSa/s dual channel ADC), including some rudimentary waveform analysis, PID loops, single cycle update rate, and a soft-core MCU backend including a GUI interface.

Since then, I've been entertaining ideas from time to time, but without a motivating need, they've mostly been idle projects, or scribbles on paper.

The high frequency design I mentioned would be DC link controlled: the inverter runs at resonance (PLL'd) and DC bus is controlled to regulate output V/I/P.  It would have analog control inputs, set by a DAC, with an MCU handling power calculation, external inputs, and HID.

Tim

[petespaco]

To what uses were you going to put your induction heaters?

*20 -80Khz ?

*500 - 2000Khz ?