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Amphenol TPC Wire & Cable Blog

Choosing the Right Cable: Ampacity Correction Factors

Posted by TPC Wire & Cable Corp. on July 11, 2019

Electric wire and cable systems are imperative to any industrial application. It's not only important to choose the correct cable for the job, it's crucial to understand the environment and the ampacity of your cable. A lack of understanding can cause your cables to fail and the entire system can come to a halt leaving you with costly downtime

Ampacity is the maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. It can also be described as current-carrying capacity. A correction factor is a multiplier that is calculated and used to adjust the amount of energy pushed through a cable based on the amount of heat that is radiated when the cable is conducting energy. The National Electrical Code table for Ambient Temperature Correction Factors can provide the appropriate correction factor based on your cable's ambient temperature rating. If a cable is used without applying the correction factor, the cable can overheat and fail.

In order to apply accurate correction factors to the ampacity value of a cable you must understand the application in which the cable will be used. This will help you determine the exact ampacity correction factor needed. Things such as ambient temperature, the number of conductors, reeling applications, and the duty-cycle can require an ampacity correction factor.

  • Ampacity can be referenced in the National Electrical Code where they list ampacity values based on ambient temperature. Should the temperature of the application differ from the referenced ambient temperature, an ampacity correction factor is applied.
  • In cable, the more energized conductors present, the more heat that is produced. Correction factors are applied when a cable holds more than three current- carrying conductors to compensate for the added heat generated within the conductors.
  • Cable on a reel with multiple layers of cable can prevent the lower cables from releasing the heat they have radiated. In this application a correction factor must be applied to compensate for the inability to release the heat in order to reduce the risk of damaging the cable.
  • Duty-cycle is the cycle of operation of a machine or other device which operates intermittently rather than continuously. In some of these applications where a machine isn’t being used regularly, specifically resistance welders, a correction factor is applied to the cables it uses based on amount of use to have the correct ampacity value.

Understanding your cable's ampacity, application, and the purpose of a correction factor is important. It can help with choosing the correct conductor size for your application and can reduce the time and costs associated with unnecessary repairs or replacement of cord and cable. Contact one of our experienced sales representatives to learn more about correction factors and how our cables can outlast the standard in situations like these. 



Topics: Environments, Medium Voltage Cable, ampacity, correction factor, reeling cable, conductor

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