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Registered Member #101
Joined: Thu Feb 09 2006, 08:12PM
Location: Wisconsin
Posts: 41
today i was just experimenting with inductoin heating. i have a zvs driver so i thought, "why not?" i heated up a 10-32 bolt to red hot in about 15-20 sec. here are some pics:
at first i ran it off of my 5 amp variac, but it was drawing close to 5 amps at only 20 volts, so i found another transformer and now i am runnig it at about 43 volts, ill check the amps later.
quick Q: does my work coil have enough/not enough turns? i tried with less turns and the coil on the ferrite core started to melt. but this many turns seems to work ok.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Nice work skmetal
That coil obivously melts because of overcurrent. You connected it with work coil with aligator clips so you have large spot resistance and heat is probably coming from that spot, and part is probably conducted trough copper wire from heated target.
If it still smokes just remove insulation from it
By reducing number of turns you actually get lesser current flowing trough the target, because of turns ratio. Getting turns closer (but not touching) may also help.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
Nice one! Are you using the ZVS circuit straigh from a flyback driver, or did you adjust the resonant capacitor for a higher frequency? For induction heating you want someting arould 200kHz, so the .68uF should probably be replaced by 100nF or so.
BTW, I like it how you managed to employ some Dremel tool parts even in this experiment!
Registered Member #101
Joined: Thu Feb 09 2006, 08:12PM
Location: Wisconsin
Posts: 41
yep the zvs, plan in playing with the cap values a little though. each cap reads ".5 MFD" i'm guessing that means .5 micro farads... one started to get hot so i put 2 in parallel. so its 1 micro farad. that is all i had laying around, but it works for now! i need to get some better caps, what type are preferred? Tantalum, polyester, Polypropylene? seems like my caps always get warm-hot (even when driving a flyback)
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
OK so you are properly just heating the iron by hysteresis losses, but still not bad. Love the ZVS
For tank capacitors which see continous high RF currents people usually prefer pulse grade plastic caps. The difference is usually the thickness of the metal film, which has to support the high currents. I have had good look with some WIMA caps, but in the US you proably have different manufacturers.
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Induction Heating
one started to get hot so i put 2 in parallel. so its 1 micro farad. that is all i had laying around, but it works for now! i need to get some better caps, what type are preferred? Tantalum, polyester, Polypropylene? seems like my caps always get warm-hot (even when driving a flyback)