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# How to Calculate Cross Sectional Area of Bus Bar

07/09/2010 8:07 AM

Hi can anyone tell how to calculate the cross sectional area of a bus bar please.

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#1

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/09/2010 9:03 AM

Dear Guest

Welcome to CR4 engineering forum

no need to be engineer to calculate the cross section, simply multiply the width of the bar by its depth.

example a 50 mm bus bar with 6 mm depth , cross section = 50x6 = 300 sq mm

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#2

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/09/2010 1:12 PM

I am assuming by cross section you are talking about the area of the end of a round rod?

If it is round, then the area of a circle is the right equation ( a = ∏ * r^2)

r^2 is r squared or r * r.

If it is a rectangular bar it is just height times width of the end.

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#7

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/10/2010 9:20 AM

To select, not to calculate,the size or cross section of busbar required for any application one should consider a)rated current of the busbar b)SC current and duration c)operating temperature and ambient temp d)conductivity of copper used e)purity of copper used(%) etc It is a very complicated affair.The solution is to consult a manufacturer or his agent by giving all site condtions

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#3

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/10/2010 3:51 AM

When holes are drilled through the bus bar, does the (hole diameter x thickness) area need to be deducted, or is it assumed that that the bolt makes up for this loss?

Inquiring (but lazy) minds wanna know....

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#5

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/10/2010 5:53 AM

Usually hole area is not deducted, the bolt will recover the lost area

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#4

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/10/2010 4:35 AM

Is this not simple Math from say 3 or 4 th year schooling?

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#6

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/10/2010 7:32 AM

Good fun. Happens when the OP swallows part of the question. My sherlock power tells me that the OP wants to know how to calculate the required busbar cross section for a given current rating .. right, guest?

(but then, all you guys knew this already)

If so, just type "busbar" in the "search" window on the right. There are far too many threads on this subject to list here.

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#8

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/10/2010 11:54 PM

give me the current raiting of the bus bar and i will tell you what is the cross sectional area of the bus bar, but u can use 1.5amps/mmsq this will be very safe

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#12

### Re: How to Calculate Cross Sectional Area of Bus Bar

12/10/2017 9:53 AM

Dear Mr.hussam,

I think your value of 1.5 Amp/MM^2 is for copper. I wish to state that the De-Rating Factor is not considered in your value, and the actual current density will be 1.5 x (De-Rating Factor)

The De-Rating Factor will vary from (0.65) to (0.80) depending on several factors and hence it will be safe to adopt a value of 1.0 Amp/MM^2 for Copper and 0.5 Amp/MM^2 for Aluminium. and Local Code also to be accounted.

DHAYANANDHAN.S

Anonymous Poster
#9

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/12/2010 11:20 AM

So far, simple math... however, what if you are trying to solve for a bar that has rounded or "filleted" corners, one method would be to draw the part in a CAD package and let it calculate the cross-sectional area. Of course, you have to know the corner radius.

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#10

### Re: How to Calculate Cross Sectional Area of Bus Bar

07/12/2010 1:44 PM

Assuming:

All four round overs are symmetrical and of the same size.

r = radius of four round overs

h = height of the bar's end

l = length of bar's end

a = resultant cross sectional area

∏ = Pi

Then:

a = (h * l) - [((2 * r) * (2 * r)) - (∏ * r^2)]

Essentially, what I did was calculate the area for a bar without round overs on the edges.

Then calculate the area of a square with sides 2 * r long.

Then calculate the area of a circle with a radius of r.

Subtract the area of that circle from the area of the square. This gives you the area of the four edges of a square that do not fit inside the circle of radius r and are the areas of the four edges of the bar that get rounded off.

Finally, subtract those four edges' areas from the total cross sectional area of the bar and you get the actual cross sectional area of the bar.

Very simple hand calculation.

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#13

### Re: How to Calculate Cross Sectional Area of Bus Bar

06/14/2018 1:00 PM

Haw to calculate crass sections Area of busbar fillet side mins full rounnd ,R4 ,R1,

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#11

### Re: How to Calculate Cross Sectional Area of Bus Bar

12/10/2017 9:43 AM

Dear friend,

The bus bar sizes/area are calculated on the basis of current density standards.

For electrical utility, the Standards are defined by International Copper Association for copper and International Aluminium Association for Aluminium,

If you refer copper association, for copper you will find the current density of 1.550003 Amp. for one Sq.MM of copper conductor, absolute value.

If you refer aluminium association, for aluminium you will find the current density of 0.625 Amp. for one Sq.MM of aluminium conductor, absolute value.

Then, this absolute current per sq.mm value should be multiplied by De-Rating Factor and there are 7 or 8 parameters are involved for arriving at the de-rating factor such as cable laid over head, or buried under ground, laid in cable trench, group of cable, and gap between cables when it is bunched, Short Circuit current level, voltage drop permissible, temp. rise in the cable permissible etc., etc..

And then your Local Code also will have a say or role.

Considering all the above 0.9 to 1.0 amps per sq.mm for Copper and 0.45 to 0.50 amps per sq.mm of Aluminium will be safe.

Pl. consult local authority or expert and proceed.

This topic is discussed 4 or 5 time in this forum and you can search in this forum. If I remember, the latest discussion - pl. open the link

DHAYANANDHAN.S

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