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Registered Member #1034
Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154
Hi Tanc, in my induction heater uses two sets of four mosfets. The sources and drains are connected directly in parallel but each gate has it's own biasing resistor and zener diode. If I could insulate the work piece well enough maybe I could get it to melt but like Sulaiman said once the temperature gets to a certain point the hysteresis losses in the iron decrease so the load starts to drop off.
Thanks for the input. Are you saying that if the insulation is good enough then even a 500w heater will melt iron? During my experiments i have suspected this to be the case. Any workpiece gets hot, glows red and sometimes orange and even yellow once or twice but it is only when the work is wrapped in ceramic fibre that things start to get interesting.
I am considering building a box for the work coil that will fully encase it in a mixture of pearlite and fire cement in an effort to reduce loss.
Last night I melted down the copper from some dead mossiest and cast some 'FET' blocks that clamp around the straight section of the work coil tubing and accept 4 mossiest each. hey ho
Thanks for the input. Are you saying that if the insulation is good enough then even a 500w heater will melt iron? During my experiments i have suspected this to be the case. Any workpiece gets hot, glows red and sometimes orange and even yellow once or twice but it is only when the work is wrapped in ceramic fibre that things start to get interesting.
I am considering building a box for the work coil that will fully encase it in a mixture of pearlite and fire cement in an effort to reduce loss.
Last night I melted down the copper from some dead mossiest and cast some 'FET' blocks that clamp around the straight section of the work coil tubing and accept 4 mossiest each. hey ho
Registered Member #123
Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162
Hi Roger,
Wow it's been some time since I logged in and now starting to play with induction heaters again. I did exactly as you mention and used Steve Wards DRSSTC driver board with manual frequency input instead of feedback from tesla coil primary.
I ran it at 20kHz (which killed my sky dish LNB because of no filters to mains).
I did the reverse of everybody else and went high voltage, low capacitance. Mine had around 100 turns of 2.5mm insulated wire wrapped around some insulated bricks and a teal coil sized tank cap.
I used a steel crucible to melt aluminium and it was much faster than my standard electric furnace.
I will see if I can dig out my old details and threads. I had to keep frequency above or below resonant as I didn't have the over current circuit running. At resonant it pulled huge power (as it would).
Hope this helps a little and I will have a dig around.
RogerInOhio wrote ...
Hi Tanc, Im glad to see things are going well . Id'd say you are doing real good to be getting 2 KW out of your system. It seems to me that if you want significantly more power it would be best to go with a circuit that uses IGBTs. The IRFP260 is a low voltage beast so the impedance of your work coil is going to limit your output no mater how many you use.
I have been wanting to build a more powerful induction heater myself and what I might do is start with a DRSST and convert it into an induction heater. I know that sounds stupid but I'm not good at designing circuits and you can buy everything you need for a DRSST premade . Don't laugh, I'm the guy that just made a crappy Tesla coil by hooking up a primary coil with a secondary coil to a induction cooker circuit board that I bought off of eBay. You cant get an more lazy than that.
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4KW Induction Heater
