# Calculating permeability of a magnetic core?

#### electronice123

Joined Oct 10, 2008
339
I have a ferrite C core set which has an AL value of 106 and an effective area of 250mm^2.

Can I calculate the core permeability with just these two values? If not what other information do I need?

#### t_n_k

Joined Mar 6, 2009
5,455
You probably also need the effective magnetic path length, since for an ideal homogeneous magnetic circuit

$$A_L=\frac{\mu_o \mu_r A}{l}$$

Where A = effective CSA & l = effective path length.

There will be a difficulty if the core is intentionally "gapped", since the air gap will dominate the magnetic circuit reluctance.

If you know AL why would you want to know the permeability?

#### electronice123

Joined Oct 10, 2008
339
Just trying to find out what it is so I can buy more.

The core has no gap and is 2 c cores placed together.

How do I measure/calculatethe effective magnetic path length?

#### t_n_k

Joined Mar 6, 2009
5,455
To find the path length I guess you take your vernier calipers and make various dimensional measurements of the core(s). Then some maths to work out the likely path mean length.
Perhaps some manufacturers have cores of similar profile and who quote path length. This might provide additional clues as how to do the calculation.