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# design of busbars

## design of busbars

(OP)
Please design a copper bus bar system for an enclosure of 2 x 1.8 x 1 mtr. The current rating of the bus is 7000 A rms at 415 V for 180 secs. Thereafter the current is 1600 A rms continuous at the same voltage.
While 7000 A is being passed the bus bar should be within permissible temperature limite. The temp permitted at 1600 A is 80 deg C. (40 + ambient 40)
I only need to know the cross section of conductor needed. No other details are required.
Exact calculation is required.
Regards
Hari Haran Rajgopal

### RE: design of busbars

Hi,

I might suggest that you pose this question on the Electrical Power Engineering it seems more like their sort of question.

Any help ?, yes no let me know.

Regards

### RE: design of busbars

Try this rule of thumb, 1000 amps per square inch for copper, 700 amps per square inch for aluminum bus bar.

### RE: design of busbars

Sounds like a college homework to me...

anyway, you can use 1 sq. inch of copper carries 1000 amps..
..the resistivity of a pure copper is ...10.2 at 32 degF ..also,

this might help too..

Area of a circle = 0.785(dxd) cir mils where d is the diameter in cir. mils

In square measure,

Area of cir mils = 0.785x1x1 =0.785 sq. mils

Cir mils =0.785d squared/ 0.785 = d squared

good luck
dydt

### RE: design of busbars

Visit www.powellelectric.com, click on the "Technical Briefs" section, and read PTB #24.  Basically the only way to be sure of the sizing is by performing actual heat rise tests.  1000 A/in^2 is not a practical way to design.  The current densities of bus bars used in PowlVac metal-clad switchgear range from 500 to 1200 A/in^2 for identical 60 C temperature rises for 1200 A to 3000 A continuous current bus bars.

### RE: design of busbars

Suggestion: Check the more officical documentation: Standards, e.g.
1. NEMA BU-1 Busways
2. NEMA BU-1.1 General Instruction for Proper Handling, Installation,
Operation, and Maintenance of Busways Rated 600 Volts or Less
3. UL Std 857 Electric Busways and Associated Fittings
4. ANSI/IEEE C37.20 Switchgear Assemblies Including Metal-Enclosed Bus
5. ANSI/IEEE C37.23 IEEE Standard for Metal-Enclosed Bus and Calculating Losses in Isolated-Phase Bus
6. ANSI/NFPA 70 National Electrical Code
7. Visit
http://busbar.copper.org/ampacity/busbar.htm
8. Search this Forum. There are some excellent postings already

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