# Inductor total winding length

Discussion in 'General Electronics Chat' started by gusmas, Sep 3, 2013.

1. ### gusmas Thread Starter Active Member

Sep 27, 2008
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0
Hi

If I want to calculate the maximum amount of turns a inductor can have (no space between the windings), do I just take the inner diameter of the core and calculate the circumference and then divide it by the wire diameter, to get the maximum amount of turns on the inductor?

2. ### wayneh Expert

Sep 9, 2010
15,554
5,763
It's more complicated than that, if you want a precise estimate. What shape are you winding? Toroid, C, E ? How many layers? Don't forget enamel thickness, wire stretching, etc.

3. ### #12 Expert

Nov 30, 2010
18,076
9,676
My transformer man had a "packing factor" of 94%. If that's as good as the professionals can do, it might be a proper goal for you.

4. ### gusmas Thread Starter Active Member

Sep 27, 2008
239
0

It is an EPCOS R40, my wire diameter is 2mm.

Apr 5, 2008
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3,769
6. ### wayneh Expert

Sep 9, 2010
15,554
5,763
If you're winding a single layer, you'll get your calculated number of turns, less maybe one or two due to imperfection. Don't forget to use the full wire diameter including enamel coating.

Also, the radius of the circumference you are winding is less than the ring, less by the radius of the wire. So I guess you have about 6mm less room than if you calculate using the ring's inner circumference.

Your wire is 12 gauge I think, and will not easily bend to conform to the ring, so you'll use a bit more per loop than the perimeter of the ring - it will round itself at the edges.