Bars cross section calculation 1

[pbeigbeder]

Hello

I must define the permissible permanent current on a existing bus bars.
Do you know which formula must be apply to define this value when I get :
Voltage : HV 13kV
width : 50mm
Depth : 5mm.
Metal : Copper
The bus bar in inside a closed local.

I have the same problem with aluminium and U profiles bars.

Thanks
P.

 

[Marmite]

The Copper Development Association in the UK has some very useful information on calculating bus bar ratings and all things to do with copper generally. Check out

http://www.cda.org.uk/megab2/elecapps/pub22/index.htm

Regards
Marmite

 

[cuky2000]

The busbar ampacity is easy determine using information available in tables. For instance, Table 13-4 from the ABB switchgear manual, 9th edition a rectangular busba 50x5 (249 mm^2) the continuous current for 35 oC ambient and 65oC conductor temperature are:

* 679 A for painted conductor up to 60 Hz.
* 583 A for bare busbar.

* 703 A for DC and up to 162/3 Hz painted.
* 588 A for DC bare.

If the condition of temperature changes, adjustment is required either using calculation or published data with similar conditions.

 

[sgtan1]

I always wondered about painted conductor. What does this mean?

And why a higher carrying capacity after painted compare to bare. By heat loss consideration or temperature rise limit you would assume the bare copper to be the limit.

Please advise.

 

[briand2]

A proportion of the heat is emitted via radiation; a painted surface will typically have a higher emissivity, so the proportion of heat emitted by radiation will be higher (more than enough to compensate for the minimal thermal insulation effect of the thin layer of paint).

Brian