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What type of Power Inductor Core

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techie

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I have designed a Simple buck converter for 48v to 24v conversion @20A. I am using a 100uH inductor at 32KHz. It is an iron powder toriodal core which is heating up a lot. Can you suggest if I should use a ferrite core instead of iron powder core.
 

Do you know what material the core is made of? And are you sure the heating is due to core losses, and not copper losses?

At 32KHz, ferrite might be a better option, but there is a huge variance within the two types, so it probably won't solve the issue unless you do some analysis first.
 

Have you checked that you are not saturating the core? I agree that ferrite might be more appropriate for the application, however, check if you are exceeding the maximum turns*current.
 

Dear techie
Hi
A big problem that will occurs at Buck systems , is simple problem ! don't forget to create the gap space at your core .
By the way , what is the size of your core ? probably , it is small for your aim ? you can select bigger core or you can use the cores in parallel with together .
And don't forget to create gap space at them.
Best Wishes
Goldsmith
 

I am not saturating the core. The current is a good triangular wave. The copper wire used for winding is 1.5mm thick. I am convinced that the heat is being generated in the core losses. So as mentioned by goldsmith, I will try using a ferrite core with either an "open bobbin" type core or a core with an "air gap" and Not use a ferrite toroid.
 

By the way , if you want know , that is your core saturated , at buck converter , you should use a very low series resistor with your inductor ( when your supply is under load ) the voltage across that resistor should be some thing like triangle wave .
( and the voltage across the inductor should be about square wave.
Good luck
Goldsmith
 

techie said:
I am not saturating the core. The current is a good triangular wave. The copper wire used for winding is 1.5mm thick. I am convinced that the heat is being generated in the core losses. So as mentioned by goldsmith, I will try using a ferrite core with either an "open bobbin" type core or a core with an "air gap" and Not use a ferrite toroid.
Click to expand...
1.5mm wire may not be thick enough for 20A depending on how many turns you have, so it may be copper losses. Unless you know the core material, and have done loss calculations on it, then I don't see why you're just assuming the core is the issue.

And powdered iron cores do not need gaps (as long as you pick the material and dimensions correctly. The "gap" is built into the material).
 

My friends
Hello
At high frequencies we will have big problem , that called skin effect , that means the current at high frequencies can not go from the center of wire , thus you should use parallel winding .
Respectfully
Goldsmith
 

Better to go for N87 grade ferrite UU core and use 30awg multiple wires 6 strands ...Core area determination is Al value in the 20Amps to give PHImax below 4500 G
 

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