The saturating current, for a coil, my teacher took from a datasheet, doesnt match with the catalog.

Thread Starter

Elektroazbis

Joined Oct 9, 2017
4
In School we buildt a buck converter unit (20MHZ). We buildt it, we tested it and it worked. The only problem is, that the coil gets extremely hot (over 100 degrees @ 3A DC current output) when we tested the buck converter. So we looked up the catalog we ordered them from to check if we used a wrong coil. But we checked and it was a coil for 5A. That is correct so that was not the mistake. Then we checked the catalog we orderder the coils from, and there it sais the coil is for 7.7A and has a saturating current of 1.7 A. Does anybody have experience with that problem? Is it a mistake or is it intentionally?

I appreciate any help and answers

PS: In the attachments there is a datasheet of the coil and a scematic of the power supply unit
 

Attachments

OBW0549

Joined Mar 2, 2015
3,566
The 7.7 amp rating may refer to the maximum current allowable to avoid excessive ohmic heating of the coil's windings, and not related to the core's saturation limit.

Looks to me like you need a coil with a much higher saturation limit.
 

wayneh

Joined Sep 9, 2010
16,400
.. it sais the coil is for 7.7A and has a saturating current of 1.7 A. Does anybody have experience with that problem? Is it a mistake or is it intentionally?
It's intentional. They're reporting two very different properties. I would assume the peak current describes the maximum continuous DC current it can tolerate without excessive temperature. The saturation current describes properties of the core. Your coil is too small for 3A, as your data are showing, in agreement with the data sheet.
 

crutschow

Joined Mar 14, 2008
25,664
You likely need a coil rated for at least 4-5A saturation current, depending upon the inductor ripple current.

Are you really running at 20MHz or is it 20kHz?
 

Thread Starter

Elektroazbis

Joined Oct 9, 2017
4
The 7.7 amp rating may refer to the maximum current allowable to avoid excessive ohmic heating of the coil's windings, and not related to the core's saturation limit.

Looks to me like you need a coil with a much higher saturation limit.
We now are going to change the coil and hope it will work, thank you very much for your help. Your responcse was very helpful.
 

Thread Starter

Elektroazbis

Joined Oct 9, 2017
4
It's intentional. They're reporting two very different properties. I would assume the peak current describes the maximum continuous DC current it can tolerate without excessive temperature. The saturation current describes properties of the core. Your coil is too small for 3A, as your data are showing, in agreement with the data sheet.
We are now going to change the coil. Thank you for helping. I was really confused about those two numbers. I think in the catalog they should write that those 7.7A are not the saturation current.
 
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