What is the temperature difference between inductor windings and case?

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Regarding the IHLP5050CE-01 (1uH) inductor, (datasheet below) do you know if there are figures for “Rth(w-c)”…ie the thermal resistance from the Windings to the top of the Case? That is, supposing the windings were at say 70degC, then what temperature would the top of the case be at?

{I suppose to test for this ourselves we would need to run a DC current through the windings (so only get winding loss and no core loss) to get them to a known temperature, then measure the temperature of the top surface?}

IHLP5050CE-01 datasheet:

**broken link removed**
 

I think that you will have to perform this experimentally,

What I would do is set a DC current (such that there are no core losses) of a value indicated on Note 3: DC current (A) that will cause an approximate delta-T of 40 °C

Since you also know the winding's Rdc, you also know the power being dissipated. For improved accuracy, you may want to temperature-correct Rdc's ohmic value from its ambient temperature value to that of the additional 40 °C rise.

Then, as accurately as possible, measure the core's outside temperature. In my opinion, this will be the issue that will require the most attention to measure accurately.

So you now have power, internal temperature, external temperature....you can solve for Rth(w-c).
 
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As stated above, the device is so small, any type of accurate contact temperature measurement is not going to be practical.
You may need to do an infra-red non contact temperature measurement.
 
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Hi,

An experimental windings temperature measurement can be done with it's DC resisrance.

Copper has a large temperature coefficient, therefore measuring U and I tells you all.
The measurement is fast an fairely precise.

Klaus
 
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thanks, roughly speaking, do you think the windings would be well thermally coupled to the top of the case of this inductor? Its a powdered iron core inductor.
 

Hi,

No, but measuring winding resistance gives the winding temperature.
And maybe you could measure the case temperature (camera?)
Then you can calculate the coupling factor.

Klaus
 
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do you think the windings would be well thermally coupled to the top of the case of this inductor?
Click to expand...
It depends. If the winding is molded (I guess, it is), you can expect roughly uniform temperature of winding and core.

In any case, most of the temperature rise specified in the datasheet will be between any inductor part and ambient. The specification is however based on a typical mount (PCB stack-up, pad sizes) if your design differs from the standard "you will have to perform this experimentally", as Schmitt trigger mentioned.
 

It depends. If the winding is molded (I guess, it is), you can expect roughly uniform temperature of winding and core.
Click to expand...
thanks...you mean there is like a potting medium in the winding window, so theres no air between windings and core?
Also, Surely the winding heat is going to couple more readily to the PCB copper pads to which the windings are directly connected, rather than to the top of the case of the inductor?

Does anyone know of a family of SMT inductors which is specifically made to be heatsunk via the top surface of the case?
 

It depends. If the winding is molded (I guess, it is),
Click to expand...
I think these inductors are mass produced by staff working for peanuts.....i suspect some are molded , but for others, mabe they just dont have time and they are not molded.
 

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