Choice of Core

S

scopeprobe

Full Member level 3
Full Member level 3
Joined
Sep 17, 2020
Messages
170
Helped
27
Reputation
58
Reaction score
99
Trophy points
28
Location
Uk
Activity points
1,939
Hi,
I'm seeking some clarification on the use of the I Squared L Graphs on Page 38 of the ferroxcube databook https://www.ferroxcube.com/en-global/download/download/11

I have a requirement for an inductance of 650uH with a peak current of 1A which if i use the I squared L equation equates to a I2L value of 0.00065 which is a value below all cores.

I've done some other maths which suggest i should use RM8 but it would be nice if i could understand how to cross reference here.

What am i missing?
 

Attachments

  • curves.jpg
    curves.jpg
    29.1 KB · Views: 25

Sort by date Sort by votes
The RM8 contour intersects y=0.00065 at around x=0.15, so this is telling you to use (at least) an air gap of 0.15mm
 

Upvote 0 Downvote
mtwieg said:
The RM8 contour intersects y=0.00065 at around x=0.15, so this is telling you to use (at least) an air gap of 0.15mm
Click to expand...
mmmm. Can you see what am i doing wrong here?

The RM8 Line looks to intersect the Y axis at 0.0045 (almost half way between 10e-3 and 10e-4 which is 0.01 and 0.001 Respectively). I'm obviously missing something as 0.00065 is a order of magnitude below all the cores which is surely wrong
 
Last edited:

Upvote 0 Downvote
The defined formulae = L = N.A.B / Ipk

so the max L available at the max I for a given max B in the core, for a given core area, and given turns - all SI units

smaller cores fit less turns than larger - using this you can soon solve your issue - even if you have to iterate a bit.

easy peasy
 
Upvote 0 Downvote
scopeprobe said:
almost half way between 10e-3 and 10e-4 which is 0.01 and 0.001
Click to expand...
No. 0.001 and 0.0001

I2L versus air gap is only half of required design parameters. You need to check if resulting N is feasible for designed current. It also doesn't consider useful Bmax for chosen operation frequency with relevant delta B.
 
Upvote 0 Downvote
You must log in or register to reply here.

Similar threads