Temperature of a conductor in free air subjected to a current.

When a conductor carries electricity a quite part of the energy is converted to heat due to the Joule effect, the heat is lost in the surrounding by convenction and radiation.

The steady-state temperature depends on a lot of factors such as the conductor resistance, current intensity, exposed surface, ambient temperature and coloring.

The conductor could be a simple electrical cable not insulated, a power cable with rectangular section but also the heating element of a resistor.

Data input

Selection of conductor material

Copper Aluminium Stainless steel (AISI 304) Silver Bronze Constantan Iron Gold Brass Titanium Tungsten NiCr 80/20 NiCr 70/30 NiCr 60/15

Material resistivity

Ohm/m mm²

Heat transfer coefficient

W/m² K

Conductor cross-section

mm²

Conductor length

m

Current which flows

A

Ambient temperature

°C

Optional parameter (not indispensable):

Inductive reactance (XL)

Ohm

Results.

Total conductor resistance

Ohm

Dissipated power

W

Temperature reached

°C

Resulting voltage drop

V

Notes.
Due to the inductive reactance, when the current is not direct but alternating the resistance increases.
In this case reactance is not considered because too variable, depending on dimensions, path and on what there is nearby of the conductor itself.

For instance, a conductor with these characteristics:

• Material = copper
• Section = 2.5 mm²
• Length = 10 m
• Path = straight line
• Disposal = near to other cables (5 - 10 mm)

It has the following characteristics:

• Resistance = 0.0704 Ohm
• Inductive reactance = 0.0019 Ohm (almost)
• Total resistance = 0.0723 Ohm