# computing rated current for inductors

1. ## computing rated current for inductors

I have a CDRH104RNP-331N and there is no current rating column in this sheet.
https://pdf.datasheet.live/datasheet...4RNP-2R5NC.pdf

It only depicts saturating current. Can rated current be computed from saturating current? 2. ## Re: computing rated current for inductors

It only depicts saturating current.
No. What do you think is the purpose of specified "temperature rise current" other than a current rating?

1 members found this post helpful. •

3. ## Re: computing rated current for inductors Originally Posted by FvM No. What do you think is the purpose of specified "temperature rise current" other than a current rating?
I suppose thats another way to state rated current since above that threshold it will raise temperature damaging the coil. 4. ## Re: computing rated current for inductors

above that threshold it will raise temperature damaging the coil.
Not above that threshold. At that current rating, it has already risen 30ºC above ambient. Other manufacturers give the rating current for increment of 20ºC. Others, also give you a Temperature vs Current chart, e.g. Wurth.

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5. ## Re: computing rated current for inductors

Hi,
According to the footnote, the temperature rise current is the current value that the inductor would rise in temperature to 50 degC from Ta=20 degC. 50 degC isn't that much of a temperature that the inductor is not supposed to withstand.

The saturation current would have the inductance drop to 65% of its nominal value. That's to say that a high (in fact destructive high) current will flow. That's what you want to avoid.

It depends more on where the product with the inductor will be used. If in an area with significant amount of ambient heat like industrial environment or automobile, then I'd say you stay below the temperature rise current value as the temperature will go higher than additional 30 degC. If it's in a domestic environment, then you can go even above the temperature rise current value, but stay well below the saturation current value.

Okay, I see that the recommended operating temperature ranges up to 100 degC so it is not suitable for automobile application.

1 members found this post helpful. 6. ## Re: computing rated current for inductors

Hi,

What is going on here.
I could not open the pdf of post #1 (I always recommend to use the PDFs directly from the manufacturer, they are most up to date)

Not above that threshold. At that current rating, it has already risen 30ºC above ambient.
According to the footnote, the temperature rise current is the current value that the inductor would rise in temperature to 50 degC from Ta=20 degC
The datasheet from manufacturer, dated (Revised: 6-Jan-17) says this:
3 Temperature rise current: the actual value of D.C. current when the temperature of coil becomes △T=40℃ (Ta＝20℃).
Klaus

1 members found this post helpful. 7. ## Re: computing rated current for inductors

A sumida datasheet I found shows a 104NP at T=40c. And the 104RNP at T=30c. 8. ## Re: computing rated current for inductors

Obviously, different datasheets revisions with different figures. The datasheet in post #1 must have been revised. It doesn't have a revision date and is from Sumida.

You should go with the latest revision then. •

9. ## Re: computing rated current for inductors

First point has been clarified, the Sumida datasheets give sufficient information about current rating.

Second point is how to read it. Assuming ΔT of 30 or 40 K for Idc temperature rise is just an arbitrary decision. You should be aware that in a usual switcher application, you have both copper and core losses. With high switching frequencies, core losses may cause a temperature rise similar to current related losses, total temperature rise is doubled then. Thus the low seeming 30 or 40 K makes sense. --[[ ]]--