OT (On Topic): Induction heater progress

This morning I put together a somewhat new bridge, which is like the old one but made with shorter, smaller copper strips and the transistors (two for starters) are all on one side. Bypass caps *line* the other side. One

0.15uF 1000V snubber cap goes from output to -V (I tried two, one to +V and one to -V, but that toasted transistors...f*ck..). Here's the waveform:

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Now I'm going to screw around with it some more, see what I can cook in the coil with just two transistors...

Tim

-- Deep Fryer: A very philosophical monk. Website @

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Reply to
Tim Williams
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Wrong clipboard doofus! You meant...

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Tim

-- Deep Fryer: A very philosophical monk. Website @

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Reply to
Tim Williams

On a sunny day (Sun, 1 Jun 2008 06:01:05 -0500) it happened "Tim Williams" wrote in :

Those are interesting waveforms, but how is it related to what circuit?

Reply to
Jan Panteltje

Roughly this circuit, but there's a lot of stuff I've updated since, oh, that page seems to be dated 1/07.

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The output stage anyway tells what you need to know about this waveform.

Sheesh, even that's wired a little differently, maybe I'll go draw another draft...

Tim

-- Deep Fryer: A very philosophical monk. Website @

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Reply to
Tim Williams

1/07.http://webpages.charter.net/dawill/tmoranwms/Elec_IndHeat6.html

Nice circuits! Thank you for making it all available online. The youtube video is cool too. Been looking at how you drive the IGBTs. Totem pole, current mirror, nice.

Reply to
panteltje

More pictures today...

Large picture of some cap banks I made up... gonna make a "induction lite" model, these are 5 x 20 x 0.1uF 275VAC MKPs, which together take up about a quarter of the space my full 200 x 0.1uF cap bank, so are probably rated less accordingly.

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Bridge I whacked together from copper strip and lots of caps. Total 2uF MKPs and 4.7uF (10 x 0.47uF) polyester bypassing the supply rails. Two

0.15uF 1000V snubber caps on the output, but one is disconnected (note tape under its lead insulating it from +V!) as it caused transistor shorts.
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Some action...

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If the coil were cooler (it was already wasting 300W for a moment before I started shooting, and I have no water cooling set up at the moment), the bit of 1/2" EMT conduit would've been yellow hot and sparking zinc fumes from the galvanizing. My proof is that I've done exactly that already, which is why its surface looks rough. So there.

This is only 400W tops, which seems to be about as much as I can get into this tank with this matching inductor. The bigger coil I've drawn as much as 800W with so far. That's not far from 320V (meter says 260~280V under these conditions), so I'll need a still smaller matching inductor to reach my ultimate power output goal I think. Peak inverter current is already up to 50A, that tank capacitor doesn't seem to be cancelling reactive current as much as I'd like it to...

Tim

-- Deep Fryer: A very philosophical monk. Website @

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Reply to
Tim Williams

That looks complex. I did one using a PIC to generate a square wave that I filtered to a sine. Put it through a big cheap audio FET amp feeding an LC head. Used the PIC ADC to measure the current flowing in the LC and keep it on resonance.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London
Reply to
Dirk Bruere at NeoPax

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