Wire Ampacity & Voltage Drop Calculator (3-Phase)
Electrical engineering tool for determining the nominal design current and calculating voltage drop across a selected conductor cross-section based on material conductivity.
Formula
\%e = \frac{100 \cdot P \cdot L}{\kappa \cdot S \cdot V^2}
P= Active Power (W)
V= System Voltage (V)
cos_phi= Power Factor
L= Cable Length (m)
kappa= Conductivity (Cu=56, Al=35)
S= Selected Cross Section (mm^2)
Quick Calculation Result
\%e = \frac{100 \cdot P \cdot L}{\kappa \cdot S \cdot V^2}
Interactive Calculator:
Active Power (W)
System Voltage (V)
Power Factor
Cable Length (m)
Conductivity (Cu=56, Al=35)
Selected Cross Section (mm^2)
-- waiting for inputs --
Result
How to Calculate Wire Ampacity & Voltage Drop Calculator (3-Phase) (Step-by-Step)
- 1
Calculate Nominal Design Current (I) from Power, Voltage, and Power Factor.
- 2
Calculate Voltage Drop Percentage (%e) using length and material conductivity.
- 3
Calculate absolute Voltage Drop in Volts.
- 4
Verify that %e is less than the maximum allowed voltage drop.
Why This Matters
In Electrical applications, correctly sizing cables prevents overheating and ensures reliable power transmission.
Material Conductivity (κ)
| Material | kappa |
|---|---|
| Copper (Cu) | 56 m/Ω·mm² |
| Aluminum (Al) | 35 m/Ω·mm² |
✓ Design Checklist
- • Verify max voltage drop is within safe limits (usually < 5%)
- • Ensure selected wire ampacity (Iz) is greater than nominal current (I)
⚠ Common Pitfalls
- • Ignoring power factor (cos φ) in AC calculations
- • Using DC voltage drop formula for 3-phase systems
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