Current capacity of uninsulated copper wire

How to calculate current capacity of copper bar molded with nylon66 material by one side of bar?
What size of crosssection area it will require to flow continious 18A current?

Are you trying to build something that must pass an inspection, code? If so then temperature rise is important. You mention uninsulated then you mention nylon66? So is it or is it not insulated? All insulation has a temperature rating regardless of the current in the conductor it may be covering/protecting.

Also you state copper wire, then you state copper bar, which is it? Bar, wire, insulated, uninsulated?

For copper bus bar there are web sites that will provide that information. As for the insulation, it must not exceed a max temperature and it must have a max voltage standoff which exceeds your nominal & FAULT voltage by a certain percentage (I can't, won't quote the margin requirement on that).

Thanks Earl,
I will correct my words.
copper bar insulated by one side with nylon66.
Continious current flowing through that is 18A.
So, what cross section area will require by copper?

Hi Abhijeet, I cant guide you to the exact calculation but below there are at least 2 links to sites where you can calculate the wires online base on IEC 60364-5-52:


http://www.cablesizer.com/iec/ampacity/

http://hto.power.schneider-electric.com/index...?lang=en-GB®ulation=EuropeCenelec#CableCSA

This question doesn't have a simple answer. It depends on what you require. As the previous answers indicate it depends on what temperature rise you are looking for. and what approval you might need.

I have some charts that show the NEC rated current for 18 ga 0.059" diameter (0.003 sq. in.!) insulated wire is 18A at 90 degrees. The fusing current of this wire without insulation is huge: 177A in 10 sec by Preece's formula or 377A in 1 sec by Onderdonk's formula, according to my chart.

In your circumstance the current in a printed circuit board might help as it is insulated on one side. The chart I have "Mil Spec Std 275 - Trace Current Carrying Capacity of Copper" indicates that a 1/4" wide trace of 2 oz. copper carrying 20A will have a temperature rise of 20 degrees C. 2 oz copper is 70 uM or about 0.003" thick.