# Forum: Analog Circuits Induction-Heating-Circuit not drawing any Current

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Hey,
I've tried to build an Induction-heating-circuit, but it doesnt draw any
current from my adjustable Transformer, no matter which voltage i give
it. I planned to run it from mains-voltage(230V-50Hz). The Inductance of
my Work-coil is around 100µH, the Work-Cap is around 330nF which gives
me a resonant frequency of 28500hz. I adjusted my Driver-IC to output me
this, and it works great. But my adjustable Transformer just shows me 0A
current. I am sure that this measurement is right, because the IGBTs
also dont get hot. Please help me!

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I think you dont need L1 and L2...only the work coil and the resonant
tank cap in series or parallel. You have a series oscillatinc circuit.

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the gate resistors are a bit too high...acc. to the datasheet, they use
a 10 Ohm Gate resistor for the given switching times. I also suggest to
use a gate driver with more power, 160 mA is too less. You want to
switch the IGBT´s fast which results in less switching losses for
IGBT´s.

For my induction heater, i use a STM32 for controlling and a MCP14E10
for gate driving with a GDT. The MCP14E10 can deliver up to 3 A.

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Joel wrote:
> But my adjustable Transformer just shows me 0A current.
With what load? Where should the energy go to?

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The energy will wasted in the LC circuit with no load (iron, etc.) in
the coil.

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at idle (no load in the coil) and control with resonant frequency, a
series resonant circuit pulls the most power, where a parallel resonant
circuit will pull at least power at resonant frequency.

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