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songsaah
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Join Date: Jan 2013
Posts: 11

Bus Bar Calculation

03/13/2013 5:24 AM

Dear all,

I calculated the maximum demand of a panel and it comes around 282 kVa.I put 20% extra and finally calculated the current
It came around 410 amps. So what should be the ampere rating of the busbar for the panel.

Please help..

Any reference documents or calculation sheets are available please provide.

Thanks in advance
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Pathfinder Tags: Busbar calculation
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Tornado
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#1

Re: Bus bar calculation

03/13/2013 5:27 AM

Around 410 amps.

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PWSlack
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United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#2

Re: Bus bar calculation

03/13/2013 6:08 AM

Duplicate thread. Busbar sizing is one of CR4's most popular topics after cable sizing:

http://cr4.globalspec.com/search/sitesearch?do=show&sort=textmatchrank&srch=busbar%20sizing&srchobjs=t%2Cc&fs=12&order=asc

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lyn
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#3

Re: Bus Bar Calculation

03/13/2013 12:09 PM

This poster, songsaah, is a DANGER TO HIMSELF AND OTHERS.

If he really is handling 400AMPS, he will kill somebody.
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nobodysomebody47
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Join Date: Nov 2011
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#4

Re: Bus Bar Calculation

03/13/2013 2:02 PM

check this please

How to size and calculate BusBar pdf and video
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jack of all trades
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#5

Re: Bus Bar Calculation

03/13/2013 3:09 PM

If you are not qualified to do the job you could get someone killed.

A 282kVA panel is NOT a toy. Do you even know how to perform mechanical strength bus and support calculations under fault current conditions to ensure the panel passes the required local electrical standards and codes.

Do you even know what I am talking about?

Ever seen an incorrectly designed panel done by someone unqualified and not following the required electrical standards explode and KILL someone!

Starting to get a better idea as to why some of us are starting to react to your posts in this way given the available information you are giving us in your posts!

....

If these are just homework questions then please say so, as I and others are playing it safe and assuming they are not.

Jack - An actual qualified panel designer and builder

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jhhassociates
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#6

Re: Bus Bar Calculation

03/14/2013 6:27 AM

I take it that you are trying to specify a panel to obtain prices from competent panel building firms, so comments about your ability to build this panel are neither relevant or helpful.

Bus bars come in standard sizes so what you need is the next standard size up from 410 amps. The panel builders will advise you as the ratings vary slightly according to your location. Bus bars are sized according to the amount of heat they can dissipate so the ambient temperature is important.

I have yet to encounter a user of control panels who is able to accurately anticipate their future demand requirements. Panels typically last for 15-20 years and some much longer. That said I think that +20% is on the low side.
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songsaah
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Join Date: Jan 2013
Posts: 11
#9
In reply to #6

Re: Bus Bar Calculation

03/20/2013 8:12 AM

what you said is exactly true. i am trying to specify a panel for purchasing.

as per your guidelines I think I should go for 630 A 50kA bus operating at 415 V (approx). Thanks for the reply.
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brzk
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#7

Re: Bus Bar Calculation

03/14/2013 6:48 AM

Hello folks,

The busbar has to be calculated for 3 systems:

_1_What you have done, so 410 Amps of installed current. Your busbar will be calibrated for 500 Amps, because it is the standard caliber next to your calculated value.

_2_You have to calculate to the short-circuit level. As I expected from your calculated installed value, your SC value will be something around 50000 Amps of thermal installed value, as per catalogues of all kinds of circuit-breakers (more or less). If you are under a transformer, this value should be very low, down to 10000 Amps according to transformer short-circuit calculations.

_3_You have to evaluate your thermal activity. I means elevation of inside temperature of your busbar, due to short-circuit + ambient temperature + lack of coolant, if your calculated temperature gives, let say, a quarter of the casting temperature of your busbar material (alu, steel or copper), you have to foreseen a cooling device (which may be only some electric fan). If this temp. will go over half the material temp., you will have to foreseen some coolant, like forced air, liquid nitrogen, etc...Because in arising its inside temp. too much time (more than once a day, for instance) your material will put a strain on it and its duration will be shortened (your busbar should have a life duration of twenty years, at least). So, by thermal overstress, you will be obliged to design your busbar with a lyre of dilatation, to absorb this thermal stress.

Designing a busbar is not something simple, which could be made by everyone.

You ought to consult a calculation consulting cabinet, before doing something (The parameters you gave were not sufficient and not exact) You should not built without having consulted, at least, one electrical engineer (and, may be, a mechanical one)

That's all, folks

BRZK

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songsaah
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Join Date: Jan 2013
Posts: 11
#8
In reply to #7

Re: Bus Bar Calculation

03/20/2013 8:07 AM

Thank you for the reply sir.That was really helpful.

As you have said the SC rating is 50kA.

Sir, You have mentioned that the parameters i have provided is not sufficent and not exact .Could you be kind enough to mention what is missing ,what additional data is required.?
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dhayanandhan
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#10

Re: Bus Bar Calculation

12/31/2013 5:46 AM

Dear Mr. songsaah,

CR4 by it self is a TREASURE. A SEARCH WITH IN CR4 will give you plenty of Information. Pl. open the Link given below and you have more than 75 topics each one will ave its own posting made by the CR4 Members.

GOOD LUCK.

http://cr4.globalspec.com/search/sitesearch?do=show&srchobjs=t%2Cc&order=asc&fs=12&sort=textmatchrank&srch=bus%20bar%20sizing

DHAYANANDHAN.S

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Previous in Forum: My Utility Company Wants to Change my Supply from 230VAC   Next in Forum: Waukesha Spark Plugs Rating.

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