I'm working on specifying parts for the following circuit:

enter image description here

I intend to have a very large work coil, (like 12" diameter) so I'm expecting to need a lot of power. I'm on a tight budget, though, so power is the tricky part for me right now. What I'm trying to do is figure out how much power I can get to the work coil for under 500$.

Looking at low-profile transformers online to start with, I found several that step-up the voltage a lot, but they have very low current ratings.

I'm not sure if that's an issue, though, because I expect that there won't be a high current-draw from the transformer. I'm thinking that the colpitt's oscillator and work coil will convert the changing voltage into a current for me, so I only need to worry about current on the transistors (or op amp) in my oscillator.

  • Am I right that I don't need a high current rating at the transformer?
  • Are my hopes realistic here (financially)?
  • What's the danger of applying too high voltage to the work coil?

Thanks a lot!

  • 1
    \$\begingroup\$ can you put a number on "a lot of power"? \$\endgroup\$ Commented Dec 6, 2018 at 22:34
  • \$\begingroup\$ @Jasen I'm aiming for the maximum possible power generation within my budget. I intentionally haven't put a number on it yet, because I'm worried that I may have to resize my load coil to fit my power capabilities. Before I get into depth on that kind of calculation, I just wanted to work through the theory -- like, what are the relationships between the currents at different parts of the circuit. That said, the power requirements will be affected by the load size, so that's why I specified a 12" diameter coil. I'll be melting a variety of metals, so I didn't specify the workpiece either. \$\endgroup\$ Commented Dec 6, 2018 at 22:56
  • \$\begingroup\$ @Jasen But, I guess to put a range on what I've been seeing so far; I'm aiming somewhere in the 10s of kW. \$\endgroup\$ Commented Dec 6, 2018 at 23:34
  • \$\begingroup\$ Vote to close as too broad. You are too vague,."work through the theory" is too broad for EE.SE. Try physics stack exchange and then narrow it down to (preferably one) EE design question. \$\endgroup\$
    – winny
    Commented Dec 7, 2018 at 8:49

1 Answer 1


Am I right that I don't need a high current rating at the transformer?

You need to pass enough energy to power the device, but other than that no. Induction heaters use a resonant circuit meaning the current (and voltage) in the work coil will be higher than in the supply.

Are my hopes realistic here (financially)?

Not enough info.

What's the danger of applying too high voltage to the work coil?

Too much current might flow, that could break something.

I'm not certain that Colpitt's is the best oscillator to use. It seems to me that this would put the resonant current through the supply filter capacitor.


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