calculate saturation current of ferrite core

Aug 23, 2014 1 Replies

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Bernhard Kuemel 11 years ago

Hi!

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

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

l_e=25.9 mm mu_e=192

Ferrite N48

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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

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legg 11 years ago

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=)

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