# How much is the permeability of this attached inductor core?

I want to use this inductor for AC line filter as line reactor. Its inductance value is 6 mH but I don't know the exact value of permeability of the material. It will be used with VFD at the input to remove the harmonics. The input current will be from 2 to 7 A.

Could you please tell me the exact value of the permeability of this material?

• Do you have a datasheet from the manufacterer? Anything else is a guess. – Colin Nov 13 '18 at 9:22
• No, I don't have a datasheet. I bought it from scratch. – James Hock Nov 13 '18 at 9:27
• Use the advice by Andy below to get the Al, but how do you know you are not saturating it? – winny Nov 13 '18 at 12:44

## 2 Answers

It looks like it has 36 turns and because inductance is proportional to turns squared we can say that the inductance for 1 turn will be 4.63 uH (4.63 uH x $$\36^2\$$ = 6 mH). The $$\A_L\$$ parameter for the inductor is the inductance for 1 turn i.e. $$\A_L\$$ = 4.63 uH/turn.

The permeability of the core is related to $$\A_L\$$ like so: -

$$\mu_e =\dfrac{A_L\cdot \ell_e}{ A_e}$$

Where le is the mean length of the core and Ae is the cross sectional area.

An example: if the mean length of the core is 5 cm and the cross sectional area is 1 cm$$\^2\$$, the absolute permeability will be 4.63 x 10$$\^{-6}\$$ x 0.05 / 0.01$$\^2\$$ = 0.002315 or, in relative terms, divide by the permeability of free space ($$\4\pi\cdot 10^{-7}\$$) to get a value of about 1842.

Get your measurement stick out!

You need some geometrical inputs (internal and external radii, height):

Be careful: permeability depends on the magnetic field, which depends on current.