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# Current Rating of a trace and its behaviour

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#### navbp

##### Junior Member level 1
Hello,

I am designing a PCB for a automotive application.
The PCB has few traces which is capable of carrying 150A of current for 12s. This is the worst case peak current for the given application.

But I need to also ensure that the same traces can handle 350A of current for a short duration (for few 100s of ms), without getting damaged. 350A is a short circuit current. The short circuit current detection will need some time to detect the over current and switch off the system.

How to calculate the melting point of the copper traces i.e., if the given trace can withstand 150A for 12s without getting damaged, then how much time can the same trace withstand 350A without getting damaged?

Thank you.

Hi,

P = I x I x R
W = I x I x R x t

you can do the math on your own. I expect about 2s.
For sure here we ignore that during that 12s a little part of heat gets spread into the environment.

Klaus

Points: 2

Points: 2