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Royer induction heater

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Fractal Universe

Tue Feb 03 2015, 07:39PM

Registered Member #4349 Joined: Wed Jan 18 2012, 01:23AM
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Posts: 13

So i finally decided to post my version of this device, i designed it to be an add-on to a MIG welder, which has a DC output of 38v max, so i went with 150 v MOSFETS and 150 v schottky diodes. The capacitance is twenty four 0.1 microfarad 400v mkp caps in parallel, although i plan on doubling it, the total power in was approx 1400 watts

the second pic is about 1 min after the first, the 1/2'' id hex nut is melting into a puddle

Claude

Sun Feb 15 2015, 09:48AM

Registered Member #3379 Joined: Mon Nov 01 2010, 06:34AM
Location: Sydney, Australia
Posts: 24

Hi fractal universe. What is on the circuit board to the side of your royer induction heater. Is it a separate gate drive?

Thanks
Claude.

hen918

Sun Feb 15 2015, 08:14PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Ohhhh, Steve, where did you get those big toroids? I could do with some.

Fractal Universe

Sun Feb 15 2015, 09:35PM

Registered Member #4349 Joined: Wed Jan 18 2012, 01:23AM
Location:
Posts: 13

hen918 wrote ...

Ohhhh, Steve, where did you get those big toroids? I could do with some.

hello, i got those on ebay 3 months ago for $8.95 each, they were labelled as RFI/EMI filters used on large 2000 watt dimmers for incandescent lamps in theatres, the seller had only 10 of those toroids i bought two of them for this IH. unfortunately the seller is now sold out,

i have no idea what the exact specs of those toroids are, on whether they are powdered iron or ferrite and what mixture (powdered iron is superior for the Mazzili IH because it does not saturate easily, even with a large DC component of current flow, like when the IH is heating a large metal piece). they are 3.5 inches O.D. wound with 60 turns of #11 magnet wire,
i have tested many toroids on the Mazzili IH and it looks like micrometals type 26 or type 52 powdered iron works very well, of course the bigger the better:) you can get those at amidoncorp.com

amidon only sells the bare toroid cores, if you choose to go this route, you will also need some wire to wind them yourself.

Claude wrote ...

Hi fractal universe. What is on the circuit board to the side of your royer induction heater. Is it a separate gate drive?

Thanks
Claude.

hello, it is the gate drive circuit; the same as the classic Mazzili circuit with minor modifications, no separate power source.
the modifications are: the positive and ground terminals feed into the GD board through ferrite toroids and a 100v 2.2 microfarad film cap connected from positive to ground, these filters protect the GD circuit from any electrical noise. the zener diodes i used are 18v 5 watt 1N5355's. the resistors are 270 ohm 5 watt metal oxide resistors. instead of using fast diodes i used MBR2015CT 150v 20a Schottky diodes; less than 0.5 forward volts (TO220 packages), using Schottky diodes instead of fast diodes makes a difference.

the MOSFETs were four (2 in parallel on each side) FQA46N15 150v 50a; which failed when i tried to melt a lugbolt, i then upgraded to four IRFB4115PBF (150v 100a ea) and those work better

since each side has 2 MOSFETs in parallel, the gates of each device is connected to the GD circuit with a ferrite bead(pulled from TV's) in series to dampen parasitic oscillations

Claude

Mon Feb 16 2015, 07:55AM

Registered Member #3379 Joined: Mon Nov 01 2010, 06:34AM
Location: Sydney, Australia
Posts: 24

Thanks for the explanation to the modifications of the gate circuit.
Claude.

hen918

Mon Feb 16 2015, 09:44PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Thanks Steve, found some nice toroids here:
I think these are the same as Amidon ones.

Fractal Universe

Tue Feb 17 2015, 05:52AM

Registered Member #4349 Joined: Wed Jan 18 2012, 01:23AM
Location:
Posts: 13

hen918 wrote ...

Thanks Steve, found some nice toroids here:
I think these are the same as Amidon ones.

those are exacly the same; micrometals cores, amidon is only a distributor.

tanc

Wed Oct 25 2017, 01:52PM

Registered Member #54853 Joined: Tue Apr 14 2015, 08:08PM
Location:
Posts: 7

hi everyone, i too am trading the marco/mazilli IH path and loving the process (unlike several of my RIPFETS!). I am currently on version 3 and I have 2 questions.

1:how do i limit the current of a rewired MOT? can this be achieved with a phase control thyristor circuit?

2:can the capacitors from microwaves be used in a tank circuit as they claim to be good for over 1500VAC?

hoping this thread has not gone cold

hen918

Wed Oct 25 2017, 03:54PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

If you are talking about using a rewound MOT as a transformer in a mazzilli circuit, you're out of luck: MOTs (or at least the old style ones we tend to call MOTs) are designed for 50 or 60 Hz, not 50 or 60 kHz, so they would be incredibly lossy even if you could get them to work.
Microwave oven capacitors are also designed for low frequencies, and I would assume (I haven't tested them) that they would also have high losses at high frequencies.

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