this inductor is removed from the car amplifier. The consumables you see are worth 150uh .. But I could not find the code of the kernel. I want to learn to order. Some are brown and some are brown-white. How can we find out what happened?
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They are called cores, as in toroidal core. They might be ferrite or iron-dust.
Various manufacturer's have colour codes for the exact type of core material, but maybe start at Micrometals and see if you can find matching colour cores, then various other manufacturers (some specialize only in ferrite, some only in iron dust, some do both I believe).
If you know the inductance and the number of turns you can calculate the specific inductance of the core from that, inductance = turns^2 x specific inductance. That should match the replacement if you have the right size and core material.
Various manufacturer's have colour codes for the exact type of core material, but maybe start at Micrometals and see if you can find matching colour cores, then various other manufacturers (some specialize only in ferrite, some only in iron dust, some do both I believe).
If you know the inductance and the number of turns you can calculate the specific inductance of the core from that, inductance = turns^2 x specific inductance. That should match the replacement if you have the right size and core material.
The core's 'nH/turns' value can be found by winding some turns then measure the inductance. As Mark says, the inductance is proportional with the square of turns.
If for instance you wind 10turns, you can measure the inductance, then divide by the square root of 10 (3.16). I would double check by winding another 10, then confirm that you get 4x the first value. (Double the turns, and get four times the inductance)
Lets say the core's value is 1000nH/turns, you will get 3.16uH with 10 turns, and 12.6uH with 20 turns.
After you know the core's value it can be easier to find something you can order.
But knowing the type of ferrite and it's frequency characteristics is different. I don't know how you can figure that one out. You need to select the type of ferrite according to the frequency you intend to use the inductor.
If for instance you wind 10turns, you can measure the inductance, then divide by the square root of 10 (3.16). I would double check by winding another 10, then confirm that you get 4x the first value. (Double the turns, and get four times the inductance)
Lets say the core's value is 1000nH/turns, you will get 3.16uH with 10 turns, and 12.6uH with 20 turns.
After you know the core's value it can be easier to find something you can order.
But knowing the type of ferrite and it's frequency characteristics is different. I don't know how you can figure that one out. You need to select the type of ferrite according to the frequency you intend to use the inductor.