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Old 04-07-2011, 12:54 AM
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Harvey Harvey is offline
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Join Date: Jul 2009
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Hi WaltersM,

You may want to look into the work of Charles P. Steinmetz and his Induction Furnace Patent. Understanding of Steinmetz Law along with understanding inductor core eddy currents can help in pinning down the cause of anomalous heat.

It would be interesting to find out if your inductors heat up in a vacuum or oil with the same thermal curves as they do in free air. Especially if the wire has any Nickle exposed to the surface.

If you are using a Mosfet and your inductor is acting like a resistor, then this would probably be the place to share your information and ask questions . This Mosfet Heating Circuits thread is a subset of the Inductive Resistor section.

The clamping from the internal avalanche diode wastes the energy into the Mosfet and is generally undesirable. There is also an effect present in AC systems that does not exist in the DC profiles, called the Proximity Effect and this too can lead to anomalous heating that is not otherwise explained.

Apart from these things, it surprises some to find out how much power is being dumped back through the inductor during the BEMF pulse ringdown. Simply analyzing that power across the internal resistance of the wire can explain much of the heating. An lastly, Harmonics are notorious for adding to the power losses and causing heating in inductive systems - being a Ham I'm sure you're familiar with that in the antenna systems and SWR scenarios.

Cheers,

Harvey
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