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DC Cable Sizing
Copper/Aluminium cable size from voltage drop and thermal derating.
ElectricalCore inputs only — quick sizing with engineering defaults.
Inputs (SI units)
Results
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Engineering Formula
- V_drop_max = V × VD%
- A_min = (2 × ρ_T × L × I) / V_drop_max [mm²]
- ρ_T = ρ_20 × (1 + α × (T − 20))
DC circuits use 2×L (send + return). Resistivity is corrected to operating temperature per IEC 60287. Cable is then rounded up to the next IEC 60228 standard cross-section.
Step-by-step Calculation
- 1.ρ at T
ρ₂₀×(1+α×ΔT)0.0189 Ω·mm²/m - 2.Max drop
V×VD%0.96 V - 3.Cross-section
2ρLI/Vd23.61 mm²
Design Assumptions
- • Two-core cable, single circuit, free air.
- • Ambient below cable ampacity limits.
Engineering Tips
- ◆Keep DC drop ≤ 2% between array and inverter.
- ◆Use MC4 connectors rated ≥ conductor ampacity.
Warnings
- ▲Verify short-circuit withstand: I²t of cable ≥ let-through of upstream fuse.
Standards & References
IEC 60228 (Conductors)IEC 60287 (Ampacity)IS 694
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Fuse & Breaker Sizing
Overcurrent protection per NEC / IEC.
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