most thermally dissipative standard wire insulation/gauge type table? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: December 10, 2018, 12:37:50 am
content: Is there a general table, that is centered around commercially available non custom wiring, that basically is sorted by highest insulation dissipation vs electrical conductivity?I can do a cursory investigation based on just ranking the materials in terms of thermal conductivity and comparing it to electrical resistance, but I don't know how coating thickness changes between materials and between things like strand count changes, voltage rating changes, other changes (maybe effect of dyes) and possibly other stuff like tinning, silver plating, possibly weave..This data is only of minor interest and I am curious if anyone knows the existence of such a table. I am not bored enough to make it myself but it would be slightly useful. There is also litz wire too. And the thermal effects of sleeves.I saw some of this data (in a mil doc) for teflon wire, it basically just said 'average wire run of x will heat to this under this load' in free space. Is there a extended standards set I can extract this from?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 10, 2018, 02:00:02 am
content: Nah, no one sorts it that way.Thermal conductivity is a material property, so just look up the stats of conventional materials. There's only a dozen of much importance.Temperature is the biggest factor in power dissipation. Higher temp wire can run more amps at the same ambient (or regular amps at more ambient).Thicker wire does dissipate a bit less power for the same maximum internal temperature, but not aggressively so because temp goes as log(OD/ID). Meanwhile, voltage rating goes as OD - ID, more or less.The most annoying part will be this: different products have different thicknesses for a given voltage rating. Only way to tell is to read lots of datasheets.And there are reasons for that. Like industrial cable with extra packing and thick rubber jacket, SOOW and the like. Really nice stuff... pricey too.Or you can just take the ampacity figures in the datasheet. It still varies wildly with ambient condition: air flow, how many other wires share the space, what the space is made of (e.g. plastic conduit vs. metal conduit or chassis). The only sure way is to build it and measure the temperature (or simulate it).Tim

author: coppercone2
author_rank: Super Contributor
timestamp: December 10, 2018, 02:59:31 am
content: Any idea of what MILSTD i am remembering?I wonder if I remember it wrong, but I swear I found one before that basically said something likeambient:gauge/strand - current 1 / temp - current 2 / temp 2 - current 3 / temp 3till the maximum before deterioration. and it had a whole bunch of different gauges with their strand count and I think it even tested if the silvering did anything.it was on page2 of some document. and it was one of those ancient re-scanned ones. \\i believe they made a formula for extrapolation too, based on a curve fit. I don't know if it had different constants for different materials, they just provided data for teflon.

author: ajb
author_rank: Super Contributor
timestamp: December 10, 2018, 07:45:14 am
content: Building electrical codes will have derating tables based on ambient temperature, but while these tables encapsulates the thermal data you're after, they don't expose it directly. They also assume particular installation conditions and wiring materials that may bear little resemblance to what you're doing, but could be worth looking at depending on what you're doing.The vast majority of people who specify wiring materials are either working to statutory building code requirements, or are more concerned with basic electrical and environmental suitability (rated ampacity, voltage drop, total power loss, physical durability). I imagine that the only people who spend any real time worrying about the thermal characteristics of their wiring are those working in military, aerospace, or physics applications. If you're that concerned about it, then as Tim said, you probably need to measure or model it yourself.

author: David Hess
author_rank: Super Contributor
timestamp: December 10, 2018, 06:33:41 pm
content: The thermal conductivity is usually dominated by the air and environment around the wire so insulation type and thickness is a secondary concern. All that matters is the maximum temperature of the insulation.