An electrical bus bar is defined as a conductor or a group of conductor used for collecting electric power from the incoming feeders and distributing them to the outgoing feeders.
Busbars are generally made of Copper or Aluminium.
An undersized busbar will result in excessive heating of the busbar under normal operating condition, leading to rise of temperature beyond permissible limits.
While, an oversized busbar will lead to a costly switchboard.
Major factors affecting Busbar Sizing are
Voltage and Current rating of the system
Enclosure Ingress Protection rating
Forced ventilation or natural ventilation
Working and ambient temperatures
Heat loss by convection and radiation
Heat generated in the busbar
Busbar current rating is normally defined as below:
1. Continuous Current rating
2. Short-circuit Current rating
Continuous Current Rating is the amperes that a Busbar will carry continuously in free air without exceeding the temperature limits. Continuous Current rating is expressed in Amperes (A).
Whereas, Short-circuit current rating is the maximum current a busbar can safely withstand for a specified time (such as 1 second or 3 Seconds). Short-circuit current rating is expressed in kilo-amperes/Sec (kA/Sec).
