# Magnet Wire Insulation

A close examination on magnet wire tables of various manufacturers like http://www.epicos.com/EPCompanyProfileWeb/Content/CABLES/Magnet%20Wire%20Data%20Sheet.pdf (page 9),shows that the ratio of the conductor area and insulation area it is not remains the same throughout the sizes of wires. Insulation building in thinner conductors, occupies more area compare with thicker one. For example the insulation of AWG #14 is 4% of the total diameter and 12% in AWG #30 (the second image it is exaggerated to show the impact).

The first question is: why there is not a constant ratio of the insulation area to the total area in all AWG conductors?

The second question is: can we take the advantage of the surface increase due to the insulation in thinner conductors and to design for more current capacity than thicker conductors?

• Why down vote this question? Nov 9, 2014 at 5:08

why there is not a constant ratio of the insulation area to the total area in all AWG conductors?

Because the important factor is the breakdown voltage of the insulation, and this is a function of thickness, not cross-sectional area.

The second question is: can we take the advantage of the surface increase due to the insulation in thinner conductors and to design for more current capacity than thicker conductors?

No, because the typical application has the wire wound tightly against its neighbors. The ability of the overall winding to get rid of heat is a function of its exterior surface area, not the surface area of the individual wires.

• However, winding several thinner wires in parallel instead of one thicker wire can help reduce skin effect. Nov 5, 2014 at 19:52
• @ Dave Tweed Definitelly the brakedown voltage it is a minor parameter for the insulation thikness. But in this case the brakedown voltage for AWG24 ia 1.6kV and 750V for AWG30 (taking Vμ=205V/μm) Nov 5, 2014 at 20:11
• @Nick Alexeev Ohh good point!! I had in my mind operation with DC only. May be more parameters involve in an AC environment. Reactance or capacitance between contactors when coiled in AC, governed by the distance between contuctors, and the distance is a function of insulation thickness Nov 5, 2014 at 20:19

You can get different insulation thicknesses. Single, heavy, triple or quad.
We buy from MWS, but this has a bit more info. I'm no expert, but I think thicker insulation is mostly to make the wire more abrasion resistant.

• Off course there is a choice of various insulations. But the final diameter of the wire will be almost the same between manufacturers, otherwishe there will be a mesh in calculation of fill factor and window utilization values. Regarding the friction (is this abrasion?),all megnetic wire manufacturers recommending a tension value for wounding. Nov 5, 2014 at 20:42
• @GRTech, No the wire diameter changes with the insulation thickness. (A quad build is thicker than a single.. for the same wire gauge.) You've got to put that into your calculations. I've mostly done air core coils on phenolic forms, with a heavy or single build of insulation. I don't know much more. I figured the thicker builds of insulation was (maybe) for coils on ferrites or iron core inductors/ transformers. If you want to put more copper into your coils they make square magnet wire. Nov 5, 2014 at 21:37
• Yes that I mean Nov 6, 2014 at 4:17