# How to Calculate the Bus Bar Size

Home Electrical Engineering Forum General Discussion How to Calculate the Bus Bar Size

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• #10705
Abdul Basit Khan
Participant

Sirs,

Can you tell me the bus bar size, we have 200kVA transformer, one 275 kVA Generator, and how we calculate the bus bar size for panel.

Regards,

Abdul Basit

#12592
smorkos
Participant

you can use bus-bars 20*10mm or up. but take care about the short circuit level and choose the bus-bars holders aacordingly.

#12590
Abdul Basit Khan
Participant

smorkos said:

you can use bus-bars 20*10mm or up. but take care about the short circuit level and choose the bus-bars holders aacordingly.

Thanks for guidence but what is the formula to calculate the bus bar size.

Regards,

Abdul Basit

#12646
Keymaster

Hi Abdul,

Smorkos is correct. You should have consider by calcualting the actual short circuit current on the system(sym & assym value) and the bus bar holder. This is the basis for calculating the mechanical strenght of the bus Bus bar calcualtion to be safe and protect for max. short circuit current (KA) during fault condiotn. The formula is not easy you have to consider the following items:

EMF between bus bar

Bus bar arrangement

Mechanical forace action supporters

mechanical force or tensile strength on bus bar

flexure of bus bar

Thermodyanmic consideration

Those mentioned above shall be consider in calcualting the bus bar

TIp: Vendor has data and formula of  bus bar size with respect to the total consumer Loas (amps)

As i can see and experience 35*4 is economically with a safe factor of 152% based on the Transformer rated current.

Hope this will help

#12744
hafsa
Participant

anyone solve this problem now? I need help…

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#12783
Keymaster

Abdul Basit Khan said:

Sirs,

Can you tell me the bus bar size, we have 200kVA transformer, one 275 kVA Generator, and how we calculate the bus bar size for panel.

Regards,

Abdul Basit

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