Induction Heating

Yes, I'm real late in putting this up. So it's going up with number three. *shrug* Anyways, where I left off was here:

Hot Getter

Heating the getter of a 12AT7, I think, for no reason at all (you could invision "reflashing the getter" and selling them for tens of dollars apiece, which I probably should do, but mind you no actual metal is evaporated - the getter is fully flashed from the factory). With the setup I could get most of the insides of such a tube red hot - about 20W plate dissipation!

Progress

This is the same exact circuit as the previous page, except with two 2SC3519's in parallel (with 0.15 ohm emitter resistors to share the current). I had originally set this up on the bench supply, but after figuring I couldn't possibly torture the poor thing any more (it was dragging the +/-15V supply down to 20V!), I switched to a different transformer. This one seen here was supposed to be a Tiny Tim Mk.2, but didn't have enough voltage (only 18V) so it was laying around until now. It's still not enough voltage, so I used a beefy double diode (on the black heatsink) and some capacitors to double it, netting 45VDC or so. I measured 40V at 5A load current at one point, so the circuit was drawing 200W -- not bad for just swapping a transformer!

Heating a strip

Here I am using it to heat a strip of transformer iron. It is worth note that this new coil is eight times the volume, yet reaches higher temperatures! The center of the hot spot is probably a bit over the curie temperature. Until I get a much greater power density, I'm not going to be getting much hotter than that, since the hysteresis loss and focusing effects contribute a lot of heating.

Part Three


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