current carring capacity of conductor

In every engineering design, there is a safety factor. This is a NEC regulation for maintaining the minimum safety factor (using 80% of the ampacity)) for the case of continuous loading (a load where the maximum current is expected to continue for 3 hours or more) of a conductor. In addition, the conductor's ampacity shall be de-rated for other factors such as ambient temperature, number of current carrying conductors in a cable, type of raceway, number of cables in the raceway etc.

- MS

Hi balujayanthi,

"Current carrying capacity of conductors " is self explanatory. It the capacity of the conductor of the cable to carry a particular maximum value of current safely with out over heating and voltage drop beyond the permitted limits. Current carrying capacity of a cable is normally provided by the manufacturer of the cable. Relevant standards also will provide the data chart for various cables.The safe current carrying capacity for a specific job is determined by calculating the de rating factors depending on various conditions of the case and accordingly reviewing the value as per local factors and conditions such as local weather, type of cable laying method,Thermal resistance of the surrounding media, permissible temperature rise etc and the factor of safety depending on the type of load. You cannot arrive at any arbitrary percentage as this safe value will depend up on the local conditions of each case.