Limy Lab / Engineering Tools

Wire & Cable Sizing

Low-voltage AC · Fixed installation · Preliminary sizing

Select conductors from load and installation conditions, with traceable calculations.

Example conditions

01 / Conductors & circuit

Single-core insulated wiresMulticore sheathed cable

Wires have separate insulation and form a circuit in conduit. A multicore cable has a shared outer sheath. PE is not a normally loaded conductor.

CircuitRated voltageVConductorInsulationInstallation

Include neutral NInclude protective conductor PE

Balanced phases, negligible neutral current, no significant harmonics

02 / Load conditions

Load inputPower definitionLoad powerkWPower factor cosφEfficiency ηDesign current allowance%

03 / Installation

One-way route lengthmAmbient air temperatureGrouped circuitsArrangementTotal voltage-drop limit%Upstream voltage drop%

Circuit count is not core count: three phases and PE serving one load count as one circuit.

04 / Protection & fault data (optional)

Protective device rating / setting InAConventional operating current I₂AProspective fault currentkAProtective clearing times

Obtain I₂ and clearing time from the protective-device data. Breaker model and trip curve are not selected automatically. Thermal check: 0.1–5 s.

Preliminary result

Preliminary sizing · Not a complete design review

Awaiting calculation

Conductor cross-section schematic (not to scale)

Basis & scope

Dataset v1 · Checked 2026-10-22

Selected IEC reference-method data, not Chinese-code compliance certification. Copper PVC: 1.5–95 mm². Aluminium: three-phase PVC only, 16–95 mm². XLPE: copper multicore only, simplified G21 ratings.

Voltage drop uses approximate hot resistance R=23.7/S (Cu) or 37.6/S (Al) Ω/km, and X=0.08 Ω/km. This conservative resistance estimate is also used for PVC; it is not product-specific measured impedance.

N and PE use the same cross-section as the phases; no reduction is applied. If PE is excluded, a separate protective conductor must be designed.

S ≥ I√t/k checks phase-conductor thermal withstand only. It does not verify disconnection, breaking capacity or earth-fault protection.

For 50/60 Hz low-voltage AC, fixed installations and equal-size conductors. Excludes motor starting, VFD outputs, DC, buried and thermally insulated routes, harmonics, unbalanced loads, parallel cables, fire requirements, terminal temperature limits, earth-loop impedance, device breaking capacity, and independent PE/N verification. Final work requires applicable standards and manufacturer checks.

Public sources for data and methods: