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Registered Member #2063
Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352
i just tried it out with 2 IRFP260 and used 2 lead acid batteries to power it up and the power cable "exploded". almost gave a heart attack. but i didnt even put a work piece inside the coil yet :(
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
Inducktion, is your 25v voltage source current limited? That would explain why the cables exploded when connected to a battery.
You need some kind of limiter: an inductor, a fuse...something. Unless you want to buy more fets, you should have protection. Voltage spikes or turning the power up a little more will fry them.
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
Hrm. Yeah. Guys, don't build this anymore, the reason mine didn't blow up was because I'm using crappy batteries that can't supply unlimited current as far as I can tell. But, I did use a power supply at school that can supply up to 20 amps successfully, and it only drew about 15 amps max from it. I'll try and think of some way to modify it so it's safe to build. Sorry Haxor! D:
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
haxor5354 wrote ...
i just tried it out with 2 IRFP260 and used 2 lead acid batteries to power it up and the power cable "exploded". almost gave a heart attack. but i didnt even put a work piece inside the coil yet :(
Did you make sure the fet's were facing the right way, i.e the source and drain aren't mixed up? Are all the wire connections correct? Also, your work coil needs to be litz wire or copper piping, thick gauge will work but will heat up a bit too much for me. The Mosfets need to be decently well heatsinked as well. I don't know why your power cable exploded, but make sure that everything is connected correctly.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
You have pretty much recreated the basic idea behind the so called "Mazzilli" driver. I suggest building that circuit, it's a very good robust design that includes current limiting and protection for the mosfet gates. It's really just your circuit with a few more resistors and diodes and an inductor.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
As you can see here
I used copper tubing that is water-cooled for the 2kw unit. It worked very well. 3/8" tubing should do well for simple heating applications such as nuts and bolts.
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
I was pondering the idea of using a schmitt trigger to activate the gates, but I don't know how I would implement that correctly. It would allow me to protect the gates and still keep it relatively simple.
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Inducktion Heater!
