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induction heating!

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LAN_403

...

Fri Dec 22 2006, 01:25AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

BP, what happens if you put a piece of Al in the primary of one of your 13mhz classe' coils? Seems like a block of Al would be a much friendlier load than a tc secondary ;)

I have had 2 experinecied with induction heating.

1. Back when I was messing with my mazilli drivers (not that I have stopped) I tried replacing the core with a big steel wrench. Running offf 12v at like 3a it would get warm, but I think about the same energy was going up in the fets.

2. Back when I was messing with SGTCs I hooked up my 7.5/30 and MMC to a variety of primaries (ended up using a whole lot of turns) and managed to heat a bolt up enough to melt plastic...

ragnar

Fri Dec 22 2006, 01:54AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

With proper transformation / LCLR setup, my more powerful class-E systems could probably get interesting results with non-ferrous metals. I'll give it a go next time I'm at my stuff.

Marko

Fri Dec 22 2006, 09:04AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Class E amplifiers are considered unsuitable for unstable loads like heated workpiece.

Load impedance would, I fear, change dramatically with temperature and different workpieces and amplifier would need to be tuned all the time to keep critical damping.

''Very high frequencies'' are no benefit for induction heating.

but it looked like to work not that way well for a powerful heater, I've got much better results with the hand-tuned 4093 + bridge LCLR driver. At 70V DC imput I was drawing just 2 Amps, heated well but not much like the same power level of the other system, and with more than 100-110V the current driven was getting really high, I've got over 8A with a 130ÂµH choke, and strangely, just a lil more heat than before. So, from what I've seen, I'm not going to suggest the royer / zvs oscillator for big heaters, just maybe little ones, or at least not direct driven.

3,5 turns is pretty little considering your coil current will be just as much smaller than workpiece current. I'm not sure if you made Q high enough for proper operation.

I believe such a circuit can be as efficient as any other topology, only being somewhat less economical for IGBT's. If you want to put any more effort in it..

Besides, board looks good... hope to see it fired up soon

Andrea87

Fri Dec 22 2006, 09:14AM

Registered Member #494 Joined: Thu Nov 09 2006, 02:42AM
Location: Udine, Italy
Posts: 31

probably I'll go for a lil easier way than class-E, my idea is to lathe a steel crucible from a steel cylinder and then drop inside it the material I'm gonna melt. Working in the 600w - 1KW range I think it would be pretty hard to set up a such powerful class-E power stage.

btw, tomorrow I'll try the PLL driver, in the worst case I'll reuse it for the secondary of the planned DRSSTC!

Hazmatt_(The Underdog)

Fri Dec 22 2006, 06:40PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I don't know how hard it would be for you to find an already made crucible, but I was able to get ahold of an Inconel crucible from a swapmeet. I think that would be a lot easier then machining one.

pixel

Tue Dec 18 2007, 09:07PM

Registered Member #1183 Joined: Tue Dec 18 2007, 08:32PM
Location:
Posts: 3

hello,

this project interresting me a lot and with your plan, I would be able to built the inductive heating, but there are pieces that I don't know what is...
If someone can show me the list with model number of each pieces using in the first design will help me to start.

thanks you

uzzors2k

Wed Dec 19 2007, 10:23AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

All of the components look labeled to me. The TBD capacitor is for timing and meant to be swapped for different frequency ranges. Despite having a simple looking schematic, LCLR Induction heaters take a developed understanding of electronics to understand and are not beginner projects. You're not ready until you can go through Richie's entire article on it and fully understand it. I would start out with flybacks transformers which are much easier to get working.

pixel

Wed Dec 19 2007, 11:33PM

Registered Member #1183 Joined: Tue Dec 18 2007, 08:32PM
Location:
Posts: 3

There are only one piece I don't find the model on internet and my distributor don't find also, if you can give me the model of D6 and D5 will be appreciated.

uzzors2k

Thu Dec 20 2007, 09:00AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Those are 400V transorbs, which are unnecessary.

Marko

Thu Dec 20 2007, 10:46AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I would much rather use SG3525 for drive since it gives you deadtime and with current design you don't have any.

If you already have UCC's you acn also use TL494 behind them.

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