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Participant

Join Date: Oct 2013
Posts: 4

# Busbar Shortcircuit Withstand Current.

10/29/2013 10:10 PM

In a LV Board. The Busbar 20x5mm Icw (shortcircuit withstand current) is 28.6kA for 0.3Sec. I want to know what will be the value for 1sec. Icw? Please explain in Detail . Thanks...

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Guru

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
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#1

### Re: Busbar Shortcircuit withstand current.

10/29/2013 10:20 PM

I don't think it works that way.

The rating is 28.6kA. It needs to hold for AT LEAST 3 seconds without damage. That does not mean it can hold more current than that if it is shorter duration. The rating at 1 second would still be 28.6kA, but you can take your time about getting rid of it; about 2 more seconds.

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Guru

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#2

### Re: Busbar Shortcircuit withstand current.

10/29/2013 11:31 PM
Participant

Join Date: Oct 2013
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#3

### Re: Busbar Shortcircuit withstand current.

10/29/2013 11:42 PM

The Busbar manufacturer give the detail like 20x5mm diameter, Icw= 28.6kA for 0.3sec. Can you say what will be current Icw for 1 sec.

Guru

Join Date: Oct 2008
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#4

### Re: Busbar Shortcircuit withstand current.

10/29/2013 11:45 PM

Per the referenced site: Conditional short circuit current for idiots- Wikipedia, the free encyclopedia

This is not really my field. I build cups for flying saucers.

Participant

Join Date: Oct 2013
Posts: 4
#5

### Re: Busbar Shortcircuit withstand current.

10/29/2013 11:52 PM

Hi

Please calculate for me and give the answer. Because I am from sales side.

Thanks

Guru

Join Date: Oct 2008
Posts: 39882
#6

### Re: Busbar Shortcircuit withstand current.

10/29/2013 11:56 PM

You won't get much help from me, cause I'm in marketing. I can tell you how great a bus bar withstands a short circuit, but I can't tell you how to lengthen one.

Guru

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#9

### Re: Busbar Shortcircuit withstand current.

10/30/2013 11:16 PM

You are in sales yet you want to be given the answer?!!

Seems like the right answer has a commercial value then. You planning on sharing some of that free love?

Ask another salesperson who might want to go back to back on any sales based on the right answer.

Try selling something else.

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Guru

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#7

### Re: Busbar Shortcircuit withstand current.

10/30/2013 1:07 AM

According to IEC60865-1 Standard, electromagnetic effects are the same not importing the short-circuit duration. Only the thermal effect is different.

According to Section 3 of the above mentioned standard "The thermal effects on bare conductors and electrical equipment" ch.3.2.4.1 Electrical Equipment

Tkr =rated short-time ; Ithr= rated short-time withstand current

Tk= new short-time ; Ith=new short-time current

If Tk>Tkr Ith= Ithr*sqrt(Tkr/Tk)

That means-according to this standard- Ith=28.6*sqrt(0.3/1)=15.66 kA for 1 sec.

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Julius
Participant

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#10

### Re: Busbar Shortcircuit withstand current.

10/31/2013 12:55 AM

Thanks to all

3
Guru

Join Date: Oct 2009
Posts: 2029
#8

### Re: Busbar Shortcircuit Withstand Current.

10/30/2013 12:09 PM

The formula is:

I21t1 = I22t2

Where,

I1 is the short time withstand current as per design = 28.6kA

t1 is the short time withstand current duration = 0.3 sec.

I2 is the short time withstand current for the desired duration

t2 is the desired duration = 1 sec.

Thus, in your case, the one second duration short time withstand current would be: 15.66kA

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#11

### Re: Busbar Shortcircuit Withstand Current.

10/31/2013 6:54 PM

It will be 28.6kA for 1 sec. In fact it will be 28.6kA all day if something doesn't melt or catch fire.

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Participant

Join Date: Oct 2013
Location: Santa Ana, CA
Posts: 3
#12

### Re: Busbar Shortcircuit Withstand Current.

11/01/2013 1:55 AM

Electrical equipment do not have any short circuit withstand capacity for internal short circuits but should have short time withstand capacity for any uncleared external fault. generally internal faults are cleared less than 1 secs (in the order of milli seconds) and in case of uncleared external fault, the bus can withstand this much magnitude of fault current upto 1 seconds with out damage. The short circuit current rating of the switchgear is I believe the RMS value and not the peak value of the short circuit current.

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