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


von Joel (Guest)


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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!

von Hermann S. (Guest)


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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.

von Hermann S. (Guest)


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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.

von Lothar M. (Company: Titel) (lkmiller) (Moderator)


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

von Hermann S. (Guest)


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

von Hermann S. (Guest)


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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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