What does this mean Current density of copper bussbars shall not exceed 1000 amperes per square inch I know it's self explanitory but would be the problem if the current density was too high?

Answer 1

Well as you said, it is self explanatory. The current density should not be more than 1000 A per square inch roughly coming to about 1.6 Ampere per square mm. Consider the case when the current density is high i.e. it could be high because of either reduced area with same current OR with more current through same area. Any of this case would lead to increase in the thermal lossess which could eventually lead to thermal runaway without the temperature rise getting stabilized (Stability being defined as temperature rise not exceeding 1 deg C per hour).

Rgds,

Fency Anthony, ABB Limited, India