Which Copper Size is More Prefferd?

Dear SolarEagle,

You are right. but current always flows on the outer surface area of a conductor, so in such case eg. for 2500A busbar system whether 4 runs of 50 x 10 is better or 2 runs of 100 x 10

(I assume) you're fretting about the skin effect. From wikipedia, "At 60 Hz in copper, the skin depth is about 8.5 mm" - so with (copper) conductors of width less than 17mm, the skin effect is negligible.

Note that the skin depth is frequency dependent and follows a logarithmic law, such that for every increase of a factor of 100^[1] in frequency, the skin depth is reduced by a factor of about 10.

[1] Edited after original posting.

Don't forget that at 8.5mm depth, the current density has fallen to 1/e that is 37% of surface value, so I would start to worry if the copper width was more than 10 to 12 mm.

Good point.

Can't you figure the difference in surface area of your two examples and answer your own question?

HOMEWORK ALERT!!!!!!!!

If the form factor is not an issue in the installation then.....

Use a single sheet 2000x1.

4000x0.5 is better still.

Skin effect negated nicely.

Good luck installing it, insulating it, mechanically protecting it and terminating to it.

What is your application?

It is also important to consider that busbars are mechanical structures as well as electrical conductors. They elongate when heated and may need flexible connections at each end. Supporting a pair of 50x 10mm bars will be more expensive than supporting a single 100 x 10mm. Mounting bars vertically improves the heat dissipation, but also reduces any deflection caused by the bars own weight. For alternating current, to work out the distance between supports and possibly the phases, calculate the weight/deflection, and the forces induced under short circuit conditions, then use the calculation that results in the shorter distance. You need the weight to work out the vertical load imposed on the supports and the short circuit force to work out the side load imposed on the supports. Unless you use sliding clamps at some supports, you will also need to know the side load imposed on the supports by the heating elongation of the bars. If the bars change direction horizontally or vertically, elongation will produce stresses at odd angles not just aligned and perpendicular to the bars.

There is as much mechanical engineering in correctly designing a large set of busbars as there is electrical engineering.

In your example, 2x100x10 will perform better than 4x50x10, since the greater number of laminations, the lower the multiplying factor will be, for example

If rating of single lamination is Y Amps

2 Laminations would be around 1.8Y

3 Laminations would be around 2.4Y

This is from memory but I think 4 Laminations is around 2.7Y (Please correct me!)

Finally please remember if you are building LV switchgear in compliance to IEC standards you will need to carry out Design Verification, whcih includes Temperature rise testing, to ensure any calculations are confirmed prior to supplying equipment.

Depends on the spacing between the laminations. Normally 1:1 for flat bars so that the bars can be interleaved at overlap joints.