Mismatch between calculated inductor design parameters and actual value obtained

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sabu31

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Hi all,
I am trying to design a 100uH inductor whose peak current is 17 A. I fixed the value of operating flux density at Bm=0.24 T (Bsat =0.32T, N87 material). With this when i calculated the required airgap I was getting approximately 0.7mm and turns as 34 ( Core selected was ETD49). However, when I wound the core with 34 turns and gave 0.7mm airgap, I was getting 400uH (approx). The desired value of inductance is being obtained at airgap of 4.5mm. Is there any mistake in calculation. I used core geometry technique for inductor design.
Please suggest what is correct procedure or related reference. Thanks.
 

double air gap and then reduce turns until you get your 100uH
 

Al values in data book for gapped ETD49 clarify that the calculated inductance can't be right. How did you calculate it?

You can follow formula for µe and Al in data book application notes. Or use calculation tool from TDK.
 

You have not listed your worst-case specifications.
-voltage
-current ripple
-frequency
-duty(max)
-even application
...
List these specs so we can calculate it too for comprison.
With these specs, efficiency will be good.

You can show how you made your calculations to get guided.
 
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