Busbar Drilling 3

[BruceC]

Hello,

Can anyone give me information on the ampacity-rating effect of drilling holes (for conductor terminations) into copper busbar?

Thank you in advance!

BruceC

 

[electricuwe]

Usually holes in busbars are not manufacturd by drilling but by punching using an hydraulic press.

The hole itself doesn`t have a significant effect on ampacity unless you are using very unusual designs.

Ampacity of a boltet joint depends on a lot of factors:


quality of surface
hardware used (size and material)
applied torque
acceptable temperature rise

If you are considering connecting a cable as a tap to a busbar the maximum temperature of the cables isolation may limit the ampacity of the busbar.

 

[yinger]

If you drill a hole in the buss bar and do not use it, it reduces the cross sectional area which lowers the current capacity linearly. However, in a copper buss bar the thermal conductions is very good and the heat is dissipated upstream and downstream from the hole which greatly mitigates this hot spot to the point of being negligable (assuming hole is removing less than 25% of the cross sectional area). If the hole is used to attach a lug or another piece of bus the greater effective cross sectional area will actually allow this section of the buss to run cooler rather than hotter.