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Registered Member #5258
Joined: Sun Jun 10 2012, 10:15PM
Location: Missouri - USA
Posts: 119
Cool. At 5MHz the depth of penetration (and thus the area where I2R heating takes place) will only be a few 10s of μm depending on the R of the work piece. You can really see that in the video too. The rod appears to be heated red hot but when removed it almost immediately cools because the internal temp was nowhere near the temp of the skin. Great demo!
Registered Member #4152
Joined: Thu Oct 20 2011, 10:18PM
Location: The Russian Federation
Posts: 108
IT IS NECESSARY TO ACHIEVE BY MEANS OF THE RESONANCE OSCILLOGRAPH IN TWO CONTOURS OR TO MAKE COMPLETELY AS AT ME select capacitor a drain - the source, yet won't be a resonance
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I would not use a ceramic for the drain-source capacitor, mica or PP film (something rated for large AC voltages) would be best. The 10uF supply cap, however would probably work great as ceramic or PP film.
I think also, if you couple too strongly to a resistive load, you might lower the gain of the system so much that it will not oscillate. You should be able to prevent this by over-sizing the work coil compared to the work piece, or limiting how close the work piece is to the coil.
I might also look at putting a clamping diode (15V bi-directional TVS would be my choice) on the gate-source of the mosfet for protection. This should allow you to add more turns on the feedback winding without risk of blowing out the gate. I think the capacitive coupling should still be OK, even with the clamping diodes.
If you power it up and it just shorts the power supply, then turn the potentiometer all the way to zero, then turn on the supply, they try turning up the pot to start the thing oscillating.
Also, i see no reason you cannot lower the operating frequency by making the drain-source capacitor larger, or using more turns on your work coil (and feedback coil).
Registered Member #1412
Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278
My induction heater start working now.Something in my circuit is dead.I change it and it works.
But it is still very unstable.I have to slowly turn the potentiometer until oscillate .Sometimes I turn it off and power it up again,it don't oscillate and short my power supply.
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
@platinum: this isn't a zvs. as far as i know it's more of an armstrong oscillator.
@zilipoper: very cool stuff you've made here. I think I'll try the circuit out myself. As mentioned by others, the skin depth of the induction heater might be low, but it still might be useful (soldering maybe?) How many turns do you recommend for the primary and feedback in both applications?
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Mini induction heater IRFP460 5 MHz
