busbar ratings

[Guest]

The busbar rating given seems to be for a single busbar in free air.

Is there a way to find ratings for multiple busbars,i.e. three

100x10 in parallel per phase, A) unenclosed

enclosed

C) insulated for A) or above

[marke]

That is correct, the ratigs are for free air only. You must derate for restricted airflow. The difficulty is just how to define the restricted airflow so that a derating can be applied.

There are numerous rules of thumb that have been applied in the industry for certain conditions, but the best thing to do, is to create the environment and make temperature rise measurements.

 

When putting busbars in parallel, it is necessary to derate to ensure that the current sharing imbalance does not cause overheating of one bar, or one point in a bar. I would normally derate by 10 - 20%. The amount of dertaing is also dependent on the spacing between the busbars. If they are very close, you will restrict the airflow between the bars and a greater derating will be required.

 

Best regards,