Unwinding an inductor

[Inu_Yasha]

I got all my parts in for my Nat P, but I need to unwind one of the inductors to reach a value. I remember someone posted a website that said how much you had to remove in order to reach a wanted value. The type of inductor is a steel laminate.

[TacoD]

I think it's not that easy, the iron core is not specified. So calculating the number of turns to take off is not straight forward. You can better use a LCR multimeter.

[mrogowski]

Agreed. There are a lot of variables.

[jimangie1973]

I use LIMP (the impedance measurement portion of the ARTA software package) to measure the impedance while unwinding inductors. All you need is the free version of the software, a resistor (preferably measured with a Ohm meter, I use 25 Ohms), your preamp/amp combo, and cables.

The SW plots the inductor's impedance magnitude and phase. Since at higher frequencies, the inductor phase is very close to +90 degrees, you can just use the magnitude and the equation magnitude = 2*pi*f*L.

So if you need a 2 mH inductor value, the impedance magnitude at 1 kHz needs to be 2 * pi * 1000 * .002 = 12.57 Ohms.

[Undefinition]

Boy was I happy when I realized Speaker Workshop can measure inductors and capacitors. Made unwinding a whole lot easier. Granted, a half-decent LCR meter only costs like $50. But that's money that could be put towards more drivers!

[Inu_Yasha]

Granted, a half-decent LCR meter only costs like $50. But that's money that could be put towards more drivers!

True true. I just guesstimated on how much needed to be removed from the inductor. I found a website that had a program that told me approximately how much to unwind. Thanks for the info though guys, I didn't know that steel laminate would be so different than air core.