Calculator Inputs
Calculation History
Recent calculations are kept in this session for export.
| Time | Material | Circuit | Length (m) | Area (mm²) | Freq (Hz) | Temp (°C) | Rdc (Ω) | Rac (Ω) | Drop (V) | Loss (W) |
|---|---|---|---|---|---|---|---|---|---|---|
| No calculations saved yet. | ||||||||||
Example Data Table
| Material | Length (m) | Area (mm²) | Frequency (Hz) | Temperature (°C) | Current (A) | Typical Use |
|---|---|---|---|---|---|---|
| Copper | 30 | 2.5 | 50 | 70 | 18 | Branch circuit wiring |
| Aluminum | 120 | 35 | 60 | 90 | 95 | Feeder conductors |
| Copper | 250 | 120 | 400 | 75 | 160 | VFD output cable review |
| Tinned Copper | 15 | 16 | 1000 | 60 | 40 | Marine or control runs |
Formula Used
ρT = ρ20 × [1 + α × (T − 20)]
RDC = ρT × L / A
d = √(4A / π)
δ = √(ρT / (π f μ))
Skin Factor = 1 + x4 / (192 + 0.8x4), where x = r / δ
RAC = RDC × Skin Factor × (1 + Proximity% / 100)
Single conductor: V = I × R
Single-phase: V = I × 2R
Three-phase: V = √3 × I × R × PF
P = n × I² × R, where n is active conductor count.
Variable meanings:
- ρ20 = resistivity at 20°C.
- α = temperature coefficient of resistance.
- L = one-way conductor length in meters.
- A = conductor area in square meters.
- f = frequency in hertz.
- μ = magnetic permeability.
- r = conductor radius.
This model assumes an equivalent round conductor and applies a practical skin-effect approximation. It is suitable for estimation, comparison, and design screening.
How to Use This Calculator
- Choose the conductor material and the circuit type.
- Enter one-way length and conductor cross-sectional area.
- Set operating frequency and conductor temperature.
- Enter current, supply voltage, and number of parallel conductors.
- Add any extra proximity adjustment when conductors are tightly grouped.
- Use power factor when reviewing three-phase voltage drop.
- Press Calculate AC Resistance to see results above the form.
- Review the graph, history table, and export results as CSV or PDF.
Frequently Asked Questions
1. Why is AC resistance higher than DC resistance?
Alternating current shifts toward the conductor surface as frequency rises. This skin effect reduces the useful conducting area, so the effective resistance increases above the DC value.
2. Does temperature matter in wire resistance calculations?
Yes. Most conductor materials become more resistive as temperature rises. Higher operating temperature increases DC resistance first, and AC resistance then builds on that higher base value.
3. What does the proximity adjustment represent?
It lets you manually include extra AC loss caused by nearby conductors, busbars, or tightly packed cable arrangements. It is useful when spacing and magnetic interaction raise effective resistance.
4. Can this calculator be used for very high frequencies?
It can show trends, but specialized RF work often needs more detailed models. At very high frequencies, conductor geometry, plating, strand design, and dielectric effects may require dedicated analysis tools.
5. Why does the calculator assume a round conductor?
Area is converted into an equivalent round diameter to estimate skin depth behavior simply. This works well for many practical wires, but flat conductors and complex shapes need more advanced geometry-specific methods.
6. How do parallel conductors change the result?
Parallel conductors share current, so the effective resistance per phase or path decreases. The calculator divides the modeled conductor resistance by the number of equal parallel conductors.
7. Is the three-phase voltage drop formula exact?
It is an estimation based on the resistive component and the entered power factor. Full cable impedance, reactance, harmonics, and installation details can change actual measured drop.
8. When should I use this tool during design work?
Use it during cable sizing, loss review, thermal checks, feeder comparisons, and frequency-sensitive evaluations. It is especially useful when temperature and non-DC conditions affect conductor performance.