Sizing of Busbar

Based on the current flows going to pass through the bus bar, we can select the size and type of the bus bar which we going to use.

BUSBAR - DEFINITION

    A Busbar is a metallic strip or bar, typically housed in switch gear & Panel boards for high current power distribution.

             

Types of Busbar

1. Copper

2. Aluminium

Sizing of Busbar

We have to choose the size of the busbar based on the amount of current which load draws from the supply.

Busbar Current Carrying capacity :

1. 1 Sq.mm of Aluminium Busbar can carry 0.8A current.

2. 1 Sq.mm of Copper Busbar can carry 1.6A current.

Example : Sizing of Copper busbar for the power load of 165 KW.

    P (KW) = √3 V I Cos Ჶ

               I = P / √3 V Cos Ჶ

                 = 165 x 1000 / √3 x 415 x (0.8)

               I = 286 A

1 Sq.mm of Copper Busbar can carry 1.6A current.

Required Sq.mm for 1A Current    = 1 / 1.6

                                                       = 0.625

Required Sq.mm for 286A Current = 286 / 1.6

                                                        = 178.75 Sq.mm 

Available copper busbar Sizes :

10 x 3, 10 x 6, 10 x 10, 15 x 3, 15 x 6, 15 x 10, 25 x 3, 25 x 6, 25 x 10, 35 x 3, 35 x 6, 35 x 10, 40 x 3, 40 x 6, 40 x 10, 50 x 3, 50 x 6, 50 x 10, 75 x 3, 75 x 6, 75 x 10, 100 x 3, 100 x 6, 100 x 10, 120 x 3, 120 x 6, 120 x 10, 150 x 3, 150 x 6, 150 x 10, 175 x 3, 175 x 6, 175 x 10, 200 x 3, 200 x 6, 200 x 10

                                                         = 178.75 / 10

                                                         = 17.8

Selected Size of the copper busbar  = 25 x 6 mm

Busbar Spacings : 

Space between the Phase - Earth should be 26mm or above 

Space between the Phase - Phase should be 32mm or above 

Busbar Support - Distance between two insulators should be 25mm and above