Short-circuit withstand capability of distribution boards 1

[JuanBC]

Hi,

Imagine we have a distribution board, MCC, Powercenter, etc. rated "100 kA 0.5 sec", does anyone know if this conversion is valid?

I²· t = (100 kA)² · (0.5 sec) = I(1 sec.) · (1.0 sec) = I(3 sec.) · (3.0 sec) ....

Is this "Equation" valid to calculate withstand capability at different times?

Thanks,

JBC
.......
"The more I read, the more I acquire, the more certain I am that I know nothing"

 

[FreddyNurk]

Not really.
The withstand combines both the short term ability to withstand the magnetic forces that may push the busbar around, as well as the longer term ability to dissipate enough heat without materially affecting the busbar.

If there's a test certificate sometimes its possible to get details of the exact tests carried out, and extrapolate based on that, but often that information isn't available. Some DB chassis arrangements have ratings that would imply that its possible (e.g. 20kA for 0.1 sec, 6kA for 1 sec) but generally they're tested for those conditions. Attempting to go from 25kA 1 second to 40kA for 0.2 seconds as an example, generally isn't possible as it doesn't take into account the magnetic forces.

EDMS Australia