Cable Ampacity Rechner — Formel

Cable Ampacity Estimation

Ampacity is the maximum continuous current a conductor can carry without exceeding its temperature rating.

Formula

Ampacity = Cross Section x Current Density x Derating Factor

Current Density Guidelines

  • Open air: 5-8 A/mm^2
  • In conduit: 3-5 A/mm^2
  • Underground: 2-4 A/mm^2

    • Derating Factors

  • Ambient temperature above 30 C: 0.7-0.9
  • Multiple cables in conduit: 0.5-0.8
  • Direct burial: 0.7-0.85

    • Always verify with NEC/IEC tables for your specific installation.

    Lösungsbeispiel

    6 mm^2 copper cable, 5 A/mm^2, derating 0.8, at 230 V.

    1. Base ampacity: 6 x 5 = 30 A
    2. Derated: 30 x 0.8 = 24 A
    3. Max power: 24 x 230 = 5,520 W = 5.52 kW