# calculate saturation current of ferrite core

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Bernhard Kuemel
Guest

Sat Aug 23, 2014 11:46 pm

Hi!

How do I calculate the saturation current of this P-core:

Ordering code: B65651+0400A048
Gap: 0.1 mm
Material: N48

l_e=25.9 mm
mu_e=192

Ferrite N48
Flux density (near saturation) (f = 10 kHz) B_S (25 °C)= 420 mT

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/toroid.html says:

B*2*pi*r=mu*N*I

So I assume substituting 2*pi*r with the core length will work
aproximately with a P-core, I do:

NI=B_S*l_e/mu = 0.42 mT * 0.0259 m / (192 * 4E-7 * pi) = 45 A

I don't believe 45 A. I have a 26/16 P-core (without specs, 26 mm
diameter, 16 mm high (per set with 2 halves)) with saturation current of
3.5 A. Even though the P1811 has 0.1 mm gap 45 A seem too large.

I want to know this before I buy the core.

Thanks, Bernhard

legg
Guest

Wed Sep 03, 2014 7:30 am

On Sat, 23 Aug 2014 19:46:32 +0200, Bernhard Kuemel
<bernhard_at_bksys.at> wrote:

Quote:
Hi!

How do I calculate the saturation current of this P-core:

Ordering code: B65651+0400A048
Gap: 0.1 mm
Material: N48

l_e=25.9 mm
mu_e=192

Ferrite N48
Flux density (near saturation) (f = 10 kHz) B_S (25 °C)= 420 mT

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/toroid.html says:

B*2*pi*r=mu*N*I

So I assume substituting 2*pi*r with the core length will work
aproximately with a P-core, I do:

NI=B_S*l_e/mu = 0.42 mT * 0.0259 m / (192 * 4E-7 * pi) = 45 A

I don't believe 45 A. I have a 26/16 P-core (without specs, 26 mm
diameter, 16 mm high (per set with 2 halves)) with saturation current of
3.5 A. Even though the P1811 has 0.1 mm gap 45 A seem too large.

I want to know this before I buy the core.

Thanks, Bernhard

For gapped structures of high permeability material (ie ferrite) the
saturation current is dependent on the gap length and turns.

B = usub0 x N x I / lg

B = flux density in teslas
usub0 = permeability of free space = 4 x pi x 10E-7
N = turns
I = saturating current in amps
lg = gap length in meters.

so Isat = Bsat x lg / ( usub0 x N )

Bsat = characteristic saturation of material used (at Temp) in teslas
lg = see above
usub0 = see above
N= see above

So, for your part Isat = .42 x 1E-4 / (4 x 3.14 x 10E-7 x 1) = 33.4A

That's for a single turn, which your formula seemed to assume (NI=)

RL

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