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Wire Cross-Section • Prąd w A

Oblicz przekrój przewodu with Prąd w A

Choose system type and material, enter current, voltage, cos φ and cable length.

Wartości obliczeń

Uwaga: To obliczenie jest technicznie poprawnym uproszczeniem typowym dla kalkulatorów online. Przy doborze praktycznym trzeba również sprawdzić normy, sposób ułożenia, temperaturę, grupowanie, zabezpieczenia, typ kabla i dane producenta.

Zastosowany wzór

Depending on your selection, the calculator uses the correct single-phase or three-phase voltage drop formula with cos φ.

Three-phase: A = (√3 × L × I × cos φ) / (κ × ΔU)

Single-phase: A = (2 × L × I × cos φ) / (κ × ΔU)

Practical guidance

Oszacuj cable size from a known operating current

Use this version when the load current is already known. It finds a cross-section from voltage drop only.

Input values explained

Prąd type
The current type determines whether the calculation uses factor 2 for outgoing and return conductors or √3 for balanced three-phase power.
Conductor material
Copper and aluminium have different conductivity. Aluminium generally requires a larger cross-section under otherwise equal conditions.
Prąd
Enter the expected operating current, not a fuse rating. Motors and electronic power supplies may draw much higher starting or peak currents.
Cable length
Enter the one-way distance from supply point to load. The required return path is already represented by the selected formula.
Napięcie
Match the voltage to the selected electrical system. Single-phase calculations use line-to-neutral voltage, while three-phase calculations use voltage between two line conductors.
Moc factor cos φ
cos φ is the ratio of active to apparent power. It is close to 1 for resistive heating loads; use the data-sheet value for motors and transformers.
Permitted voltage drop
This percentage limits the calculated voltage loss. It is a design assumption and must suit the circuit and applicable requirements.
Conductivity κ
κ is the calculation value for the conductor material. Common approximations are 58 for copper and 37 for aluminium; heating increases actual resistance.

Example: 16 A over 25 metres

Assume balanced 400 V three-phase, copper, 16 A, 25 m, cos φ 0.90 and a 3% voltage-drop limit.

A = (√3 × 25 m × 16 A × 0.90) ÷ (58 × 12 V) ≈ 0.90 mm²

Napięcie drop alone points to the next standard size, 1.5 mm². This does not prove that 1.5 mm² can carry 16 A in the intended installation.

Not a complete cable design

Treat the result as a voltage-drop minimum. The final size must satisfy ampacity, fault protection and disconnection requirements as well.

Calculation limits

  • Installation method, ambient temperature, grouping and loaded-core count are missing.
  • Cable type, minimum sizes and protective-device requirements must be checked separately.