Current capacity of 0.5sq mm wire

[Murugesh_89]

Hi,

How much maximum current does a 0.5sq mm and 0.25sq mm wire can able to carry? What is the safe value of current to pass through it?

I search many sites and got variable values. Can anybody give me a correct suggestion..

Thanks,
Murugesh

 

[rusty81]

These are approx AWG 20 (0.8 mm in diameter, 0.5 sq mm) and AWG 23 (0.56 mm in diameter, 0.25 sq mm), the maximum current should be 1.4A and 700mA (safe values) for copper wires.

 

[FvM]

I search many sites and got variable values.

We have to ask under which conditions, e.g. single wire or in a multi-conductor cable.

the maximum current should be 1.4A and 700mA (safe values) for copper wires.

Seems rather low, I see numbers of 3 to 9 A for 0.5 sq mm.

 

[rusty81]

3-9 A for a 0.8mm diameter? Solid or multiwired cable?
Is too much, is going to melt down.

 

[BradtheRad]

The first link below...

States 2.0430 A as the maximum for 20 AWG.

For 23 gauge, it is 1.0190 A.

These figures are based on 500 circular mils per A.

Links to charts of wire gauges showing ampacity:

http://amasci.com/tesla/wire1.html



http://www.powerstream.com/Wire_Size.htm

 

[dick_freebird]

Practically, this may be less about the wire than its
insulation temperature rating and how it is enclosed
(cooled, or not). Bare copper can stand a lot more
self-heated temperature than PVC for example, and
the conductor may be unaffected but the insulation
fail (although this may bring on the next act, Short
Circuit Follies). This is why people ask about the
application details.

 

[FvM]

3-9 A for a 0.8mm diameter? Solid or multiwired cable?
Is too much, is going to melt down.

There's no essential difference between solid or stranded.

9A and 0.5 sq mm results in about 28 mW/cm power dissipation. Not a big thing.

The quoted numbers apply to cables respectively single insulated wire in air. Current capacity of magnet wire in a winding will be considerably lower.

You'll find similar numbers in Brad's third link, it specifies 11 A for AWG20 chassis wiring. https://www.powerstream.com/Wire_Size.htm

Voltage drop considerations may suggest larger cable cross sections than permitted by maximum amperage.

 

[rusty81]

I toke the same link : https://www.powerstream.com/Wire_Size.htm

but i reported maximum current for power transmission (with a bit of safety margin), that was in my thoughts the most reasonable value, based in past experience as well.

 

[FvM]

I think we are partly discussing on cross purposes, mainly because the field of application hasn't be clearly specified. Most people involved in instrument design will know which amperage is permitted by national and international standards e.g. for power supply cables or internal wiring. As an example, I quote the UL-CSA rules, which are probably a bit more restricted than other standards.