@meanu there is a seller on ebay that has capacitors sufficient for a 10kw induction heater and it will probably cost you about 45$ just for the capacitors.
however i can't recommend them until either i buy one and test it (i'm intending to within about 6 weeks) or the seller replies to my inquiry.
in any case, a 10kw induction heater isn't a trivial project, neither is a 1kw unit.
here is a few things i've run into:
1)if you make the whole system too efficient then its too easy to blow up.
This means you're forced to build a PLL to keep it happy, as well as peak current detectors and glitch detectors to keep it happy.
2)I am already looking to sensing the tank current with a rogowski coil rather than a current transformer, because methods of peak current detection are sensitive to noise, (and putting a current transformer on the tank isn't acceptable). RC snubbers sufficient to dampen the current waveform (the square wave out of the inverter has to drive the parasitic capacitance of the transformer and that's essentially hard switching) introduce a phase shift and this means its not kept in resonance. If you provide extra inductance between the inverter and the transformer, then you increase the inverter KVA required, and that inductance resonates with the parasitic capacitance of the transformer. -it ends up being a mess.
3) A wide range of loads (iron, or did you want copper melted?) require a variable voltage power supply set to constant current mode (as limited by the inverter)
4) it is often desirable to be able to switch the transformer ratio at will, unless you wish to just over engineer the transformer and use a 30kva transformer for a 10kva tx.
regarding the last point, the only way i would even consider building an induction heater today is the transformer fed series resonant tank.
take the work coil, capacitor and transformer in series. change the turns ratio to match the current and voltage of your inverter.
at resonance, the inverter current is a sine wave, at 100% power factor.
turn off and turn on losses are thus mostly negligible.
regarding the comment that it is easy to blow up:
in theory, if you drive the inverter from an ideal current source, as long as the switches can handle hard switching at leading or lagging power factors, you Cannot blow anything up.
the problem is if its too efficient the energy stored in the tank will be dumped out back into the power supply if the frequency changes, and it may be sufficient energy to blow up the inverter.
to solve that problem you can over engineer the inverter or just connect more capacitors across the inverter.. and all of a sudden, an ideal current source is buffered by rather large capacitors, and it is no longer ideal.
another problem:
assuming your inverter is a two level square wave inverter, supposing there is a glitch and the high side switches don't turn on (high side driver doesn't have enough voltage on the bootstrap capacitors?) then you get a dc bias in the transformer.
there's two ways to solve that problem.
use a transformer to drive all the switches properly. or. connect the inverter to the transformer with a capacitor in series.
you are looking to build a 10kw system, this means you need to build the inverter for 20kw, and a capacitor rated for the dc voltage feeding the inverter, and enough microfarads to provide a relatively low impedance aren't cheap, unless you buy them on ebay for $20. again, i would provide links but i only know of a few sellers and i'm not about to go scrolling through 200,000 capacitors looking for coke can sized film caps. I can go into detail on how to identify the capacitors you need for the tank coil, the dc link filter, and the ac coupling between the transformer and the inverter if you need more clarity.
that said, if you are willing to spend three hours soldering lots of small capacitors together, don't throw out the idea of using a lot of small ones.
here is a photo of a 1 kw unit, capacitors, transformer and work coil
**broken link removed**
**broken link removed**
look in the parent directory for build photos.
i'm about to build a proper tutorial and throw it all on my website, so don't take any of this personally....
let me know if you need any more help.
I am looking to throw together a decent PLL and gate driver into the open source community/provide boards if group orders persist.