# Homework Help: Electromagnetic forces in Three Phase Copper Busbars (Rectangular)

1. Oct 12, 2011

### benyzk

1. The problem statement, all variables and given/known data
So here is the Problem :

I am Modelling an interesting problem for a project i am busy with. I need to find out the force exerted on a single busbar in a 3 phase system, with each phase carrying 3300A.

This is mainly so that i can deduce what size of busbar supports i should be using so as to handle the worst case scenario induced magnetic forces between the busbars. Assume a short circuit current of 25KA.

i am attaching a very simplified model of the problem to this post.

i have also modelled the problem using FEMM (which i will attach to the post as well) and from there i am able to calculate the forces between the busbars in the using the force from stress tensor function. For anybody who is familiar with this force, can i assume this force to be that between the busbars

Also my second problem is that the model assumes that there is 3300A running through the busbars with the Go current and -3300 running through the busbars in the return Busbars (during normal operations) However, this is not true, because in 3 phase, the currents will be offset by 120 degrees at any point in time. What effect(Magnetically) does this have on the busbars? does the force remain the same as though the current in teh phases is 0 degrees apart?

Any help / brainstorming will be greatly appreciated folks. Thank you.

#### Attached Files:

• ###### model.zip
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Last edited: Oct 12, 2011