Electrical Bus Bar Size Calculation

Required ampacity range amp.

Electrical bus bar size calculation.

Calculation of busbar will denote by millimeter. Calculate bus bar cross section area calculate current rating of bus bar calculate peak elector magnetic force between phase conductors calculate force on insulator of bus bar support. Consultant challenged contractor that. The bus bar 100mm x25mm x1 5mm is suitable for incomer current 100 25 1 5 1 2 4500a.

Table 2 indicates that 1 16 x 1 in. Now total ampere we can get. Ampacity of the bus bar selected must then be verified by checking table 1. Assume that required ampacity is 185 amps at 30 c rise.

Typical size of the busbar available in the market. Then check previous table to verify that size selected has the necessary ampacity. In case of copper bus bar the current carrying capacity is 1 2 max. Example of busbar calculation.

In case of aluminium bus bar the current carrying capacity is 0 8 max. 25 x 5 25 x 8 25 x 10 30 x 5 30 x 8 30 x 10 40 x 5 40 x 8 50 x 5 50 x 8 50 x 10 80 x 5 80 x 8 80 x 10 100 x 20 110 x 10 sqmm etc. Consultant recommended busbar size based on the thumb rule we noticed busbar size is low to carry 6300a. Knowing required ampacity determine possible bus bar dimensions from the table.

Let s consider we have a 600kva power transformer or a generator which have 400v as line voltage. Bus bar cross section area as per short circuit 626 sq mm select higher size for bus bar cross section area between 436 sq mm and 626 sq mm final calculated bus bar cross section area 626 sq mm actual selected bus bar size is 75 10 750 sq mm. The total current carrying capacity of the busbar is 1 2 area 1000 sqmm 1 2 1200 amps. Dc current when dealing with dc power the biggest concern is resistance per foot and the resulting voltage drop.

For example a 1 16 x 1 2 inch bus bar has an area of 0 0312 inches square and the equivalent circular area of 39 7 circular mils. When you are calculating the size of a busbar then you have to keep in mind its height and thickness of conductor plate that you use. So the bus bar 100x25x1 5 is suitable for 100 25 1 5 0 8 3000a incomer current. So for our load 80 x 5 or 40 x 10 or 50 x 8 sqmm busbar enough is enough.

He is member of institution of engineers mie and ceng india. Now you have to make a cable connection with busbar. Busbar size should be equal or more than of 6300a. Size would probably be adequate.