I am confused as to why bus bar ampacity tables show a higher ampacity of bus sizes with a higher degree of temperaturs, i.e. 50 deg. C apposed to say 75 deg. C.
anybody know?
it is the temperature rise. a 75degC rise busbar is carrying more current than a 50degC rise one. if a given size of busbar is made (by cooling) to support a temperature of 150degC and carry a current of 1000 amps say, the same busbar will carry less curent if it made to support a yemperature 100degC
The current carrying capacity of any bus is determined by the amount of current the conductor can accommodate for a given temperature rise. Current carrying capacity can be considered a function of temperature rise.
The greater the ability to dissipate heat the greater the current carrying capacity. So higher the temperature allowed in the conductor,higher current it can take.