We are doing a project on waste plastic melting, so that it could be extruded into wires. For heating we are attempting induction method. For simplicity we have purchased the commercial induction cooktop driver circuit (2200W). We will replace the pan-cake type coil with a "multiturn OD" geometry, to be made from 5 mm copper tube coiled at a radius of 100mm. We need help on calcualtion of number of turns and the required capacitor bank.
If one can guide us, or point to some design literature, then it would be nice.
Attachment: photo of driver circuit and capacitors. (Capacitor-1.jpeg refers to the coil side capacitor.)
Hi Sushanta, I would start by disconnecting the pancake coil and measuring its inductance with and without load (cooking pot). It should be about the same in both cases since the cooking pot will introduce mainly a resistance parallel to the inductance.
Knowing the inductance and the desired geometry of the replacement coil, one can determine the number of turns using approximation formulas. BTW, does "OD" just stand for "outer diameter" or has it another meaning (possibly a typo for OL = one layer)? Knowing completely the geometry (length?) of the coil, I could look up a formula in a handbook for electrical engineers.
Next step would be to measure the actual inductance of the new coil, and correcting it if necessary, before connecting it to the driver board. I don't think that you have to change or add any capacitors.
A possible problem could be the field of the coil: You have to make sure that it doesn't introduce unwanted eddy currents, for example in the heatsink on the driver pcb.
On another level, I know that plastic can be melted by applying capacitively an RF field; I would have thought that applying the field inductively would be hampered by technological problems but I might be mistaken.
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