# Current ampacity for small swg conductors

Discussion in 'Physics' started by amilton542, Feb 7, 2012.

1. ### amilton542 Thread Starter Active Member

Nov 13, 2010
494
64
I want to calculate the current carrying capacity of small copper enammelled wire guages.

Everything I look at is AWG, and their cross-sectional areas are too big. I'm after an swg table but can't find one.

Is there a formula I can use to determine the current ampacity?

2. ### bertus Administrator

Apr 5, 2008
15,648
2,347
amilton542 likes this.

Nov 13, 2010
494
64
Thank you.

4. ### Kozmyk New Member

Aug 22, 2011
2
1
A lot of the data in tables giving ampacity per wire size is application related. Mainly to mains power installation.
These include safety margins for heat dissipation, cable bundling, insulation melting points etc. and are not the maximum ampacities for a single conductor in free air.

The ultimate maximum would be at the point at which the conductor fails i.e. melts or breaks.
Clearly you have to work back from that state.

amilton542 likes this.
5. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
513
You will find the information you seek in publications by

The Radio Society of Great Britain (RSGB)

eg

The Radio Data Reference Book by Jessop, p221 references current ratings and other data for SWG copper.

What SWG are you interested in?

6. ### amilton542 Thread Starter Active Member

Nov 13, 2010
494
64
I'm interested in 24 SWG, but after looking at the conversion table Bertus gave me, the closest approximation in wire diameter was 24 AWG; which was close enough.

For 24 AWG i've got 577mA.

7. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
513
My tables have the following data for 24 swg

diameter 0.022 inch

resistance of 1000 yards 63.16 ohms

length in yards per pound 228.3

current rating 0.4561 amps at 1200 amps per sq inch

Turns per linear inch

Enamel 41.6
Single silk 42.1
double silk 40.0
Single cotton 36.7
Double cotton 31.0

Turns per square inch

Enamel 1731
Single silk 1772
double silk 1600
Single cotton 1347
Double cotton 961

Nearest american wire guage 23

8. ### amilton542 Thread Starter Active Member

Nov 13, 2010
494
64
Thanks studiot.

I don't suppose you know a good method on how get your hands on the other end of the conductor that is embedded inside a bobbin of coil like this http://www.maplin.co.uk/enamelled-copper-wire-44

I can do it buy hand and get it nice and tight so it looks exactly how it did before, but to do it by hand to eight bobbins of 24 SWG copper wire will take me days.

I was thinking of a drill set-up, but I think it could prove awkward trying to get the windings tight.

9. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
513
Both the RSGB and Babani publications had practical amateur coil winders based on hand drills and sewing machines etc. I have also seen Knitmaster hand cranked wool winders pressed into service.

The main issue is a turns counter. Some electronics mags of yesteryear had designs for this. You can also modify a bikeometer or wheeled pedometer mechanism for this.

amilton542 likes this.