REQUIRED CONDUCTOR SIZE TO MEET MAXIMUM SPECIFIED TEMPERATURE LIMITS UNDER
SHORT-TIME OVER-CURRENT CONDITIONS

The following calculator computes required conductor size to stay within the conductor's maximum specified temperature given a short term overcurrent condition. The calculator allows for the material to be either Copper or Aluminum.

The calculator uses empirical formulas that consider all heat generated by I2R losses in the conductor during overcurrent condition to be absorbed by the conductor and that no heat is transmitted from the conductor to its surroundings.

Calculator-1

Known variables: Over-current Time (Seconds), Over-Current Magnitude (RMS Amperes), Conductor Material, Operating Temperature (°C), Maximum Temperature Limit (°C)



     
Input Conductor, Current, and Temperature Details  
Choose Conductor Material:
 
Input Over-Current Time:   
Input Overcurrent Magnitude:   
Input Operating Temperature:
 
Input Maximum Temperature Limit:
 
     
Required Conductor Size  
Minimum Conductor Size Needed  Circular Mills  
       
       

Formulas and Variables

Copper Conductors





Aluminum Conductors


Where:

T = Time Duration of Short Circuit/ Overcurrent Condition (seconds)
T = Over-Current Duration (seconds)
θ1 = Operating Temperature (degrees Celsius)
θ2 = Maximum Temperature (degrees Celsius)
A = Cross-Sectional Area (Circular Mils)
I = Short Circut / Overload Current (RMS Amperes)

Conductor / Cable / Bus Bar Data

Tables below provide circular mil and area information for various size conductors and bus bar for reference purposes.