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IS it possible?

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Inducktion

Tue Jul 05 2011, 01:47AM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

If you're going for series resonance, go with

along those lines, and with parallel, use

series and parallel resonance both have their own little perks. Series has less component counts, and is generally more powerful than parallel, but it may draw too much current for your power supply to handle. Parallel is lower power. Either way, both will work. With parallel, though, make sure your matching inductor is between 20 turns to 30 turns on a ferrite core of some sort. Flyback cores will work for lower power, if you're going higher, use a larger core.

Platinum

Tue Jul 05 2011, 02:28AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

How do I wire the transformer, I can use a flyback core, how many turn is it, thanks man.

Dr. ISOTOP

Tue Jul 05 2011, 08:47AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Mine switches at 65 Khz into a 20:1 matching transformer, ~3.5 uH work coil, 3.75 uF tank cap, and pulls 2.5A@20V tuned for ZCS and 3A@20V tuned for max power. Twiddle the ratio accordingly for your supply, keeping in mind whatever FETs it has in it will become *very* sad as current goes up.
I like toroidial transformers, as they couple well with a 1-turn water-cooled secondary side.
It'll be very hard to pull this off with no frequency adjust and no scope!

Platinum

Wed Jul 06 2011, 01:24AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

Well it is going to be hard without a 'scope.

Platinum

Wed Jul 06 2011, 06:49AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

Ash Small wrote ...

adding a capacitor in parallel with the work coil will give a simple resonant circuit. the capacitor and coil will have a resonant frequency, but this will vary with different workpieces and will vary as the workpiece heats up.

most circuits will also have a series capacitor and/or a series inductor, at minimum.

The idea is to match the resonant frequency of the work coil/parallel capacitor to the frequency of the transformer. There are basically two ways to do this, one is to use variable capacitors, and maybe a variable series inductor. The other way is to use a feedback loop from the resonant circuit to drive the transformer at the same frequency. This is the method that most people use for induction heaters. It is also the method that the Mazilli ZVS circuit uses.

If your transformer outputs a fixed frequency you'll have to match the coil/capacitor pair to that frequency using variable capacitors, etc.

HEY!

Hey Ash I got a variable capacitor from a old radio, will it work?

Ash Small

Wed Jul 06 2011, 09:42AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Platinum wrote ...

.
Hey Ash I got a variable capacitor from a old radio, will it work?

It will almost certainly be too small (too low a capacitance value) to use on it's own.

There is also the voltage rating to be considered, the voltage can increase in the resonant circuit.

You may be able to use it in parallel with other capacitors for 'fine adjustment'.

The coil, with workpiece, and the capacitor need to resonate at the same frequency as the transformer, and, as I said previously, the inductance changes with different workpieces and as the workpiece heats up.

You will first need to know the approximate frequency, and the approximate inductance before you can work out the approximate capacitance required, then use the variable capacitor for 'fine tuning'.

This will be almost impossible without a 'scope, or some means of measuring frequency.

Platinum

Thu Jul 07 2011, 04:02AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

OK So the halogen transformer arrived today, and my multimeter.

The postage was ages, and they were both wrong one's sent out, but I'm not going to complain, atleast I have one now.

So I setup the halogen xformer, attached it to my largest flyback, and it was output very, very low.

I had 10 turns on the primary. And it was outputting as if I was switching the whole thing off every second.

The the fuse inside the halogen xformer blew, I replaced it, then it blew again, why is this?, the fuse way the right rating too.

And when the fuse was still OK, the heatsink on the transistor is warm, so I thick it's still OK.

But why is the fuse blowing? is there anyway I can bypass it or something?

Update:

This box of the transformer

sais line current : 0.88A, and the fuse is 2A, so I used a 1.6 one and 5A one, still the both blew what is causing this?

Patric

Thu Jul 07 2011, 08:29AM

Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255

Fuses are not to embarrass people, but to protect a circuit.;-)

Platinum

Thu Jul 07 2011, 08:32AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

Please only post help.

Ha. Anyway Maybe there is a short circuit in the board, but I've checked and there isn't, what is causing it to blow all the time, I've wasted like 5 fuses.

Dr. ISOTOP

Thu Jul 07 2011, 12:56PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Platinum wrote ...

Please only post help.

Ha. Anyway Maybe there is a short circuit in the board, but I've checked and there isn't, what is causing it to blow all the time, I've wasted like 5 fuses.

Well, he was helping, ya know...
If you're pulling too much current out of the halogen transformer, the fuse will blow.

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