Electrical Schematic Editor — Ladder Diagrams, Cable Sizing & BOM (IEC 60617 / IEC 60364)
Governing standard: IEC 60617· IEC 60617 symbol library · IEC 60364-5-52 cable sizing (current capacity & voltage drop ≤ 3 %)
The MechanixCalc Electrical Schematic editor is a full-featured, browser-based drawing tool that lets engineers compose power and control circuit diagrams using the IEC 60617 international symbol library. Lay down contacts, coils, motors, sensors and bus lines across as many sheets as the project requires, then run the built-in cable-sizing engine — which selects the minimum conductor cross-sectional area (CSA) to IEC 60364-5-52 and checks that the voltage drop stays within the 3 % limit — without leaving the editor.
It is built for electrical design engineers, panel builders, and machine-designers who need a single environment to document a complete machine electrical system: from the 24 V control rung through to the motor power circuit. The finished design exports to PNG, SVG, or a branded PDF engineering report that carries the full symbol key, bill of materials, and cable schedule — giving reviewers and commissioning teams a self-contained, reproducible document.
What this calculator does
- IEC 60617 electrical symbol library — contacts, coils, motors, transformers, sensors, terminals and more
- Ladder diagram editor with numbered rungs, configurable across multiple sheets
- Power, control, signal and bus line types with distinct colours and styling
- Cable-sizing calculator per IEC 60364-5-52: minimum CSA, current-carrying capacity (XLPE / PVC, copper / aluminium), and voltage-drop check (≤ 3 %)
- Parallel-conductor recommendation for loads that exceed the highest single-conductor ampacity in the table (IEC 60364-5-52 §523.2)
- Automatic bill of materials with device counts, tag references and CSV export
- Export to PNG, SVG or branded PDF engineering report
Method & formulas
Symbol library and diagram structure (IEC 60617)
Every component placed on a sheet is drawn from the IEC 60617 graphical symbol database — the international standard for symbols used in electrotechnical diagrams. The editor enforces the rung-based ladder convention: contacts are placed on horizontal rungs, coils are placed at the right rail, and each rung is numbered sequentially. Horizontal lines carry the circuit signal left-to-right; vertical power rails carry the supply voltage. The multi-sheet model lets a motor power circuit live on Sheet 1 while the associated PLC I/O rungs sit on Sheet 2, with cross-reference tags linking the coil to its contacts wherever they appear.
Cable sizing — current-carrying capacity (IEC 60364-5-52)
IEC 60364-5-52 tabulates the sustained current-carrying capacity (ampacity) of cables by conductor cross-sectional area, insulation type (XLPE or PVC) and conductor material (copper or aluminium). The sizing engine scans the applicable table to find the smallest CSA whose rated ampacity meets or exceeds the design load current, so the cable is never thermally overloaded in normal continuous service. For aluminium conductors the copper ampacity is multiplied by the IEC derating factor of 0.78, consistent with the higher resistivity of aluminium (ρ_Al ≈ 0.028 Ω·mm²/m vs ρ_Cu ≈ 0.0175 Ω·mm²/m).
When the load current exceeds the largest entry in the applicable table — the 95 mm² conductor — the engine flags the result as overrange and calculates the minimum number of parallel conductors required. Parallel conductors carry equal current when they are the same length, CSA, insulation type, and routing (IEC 60364-5-52 §523.2), so the required parallel count is simply ⌈I_load / I_max⌉.
n_parallel = ⌈ I_load / I_max ⌉where n_parallel = minimum number of parallel conductors; I_load = design load current (A); I_max = rated ampacity of the largest available single conductor in the table (A); ⌈·⌉ = ceiling function (round up to nearest integer)
Voltage-drop check (IEC 60364-5-52 / IEC 60364-8-1 ≤ 3 %)
After the minimum CSA is selected on an ampacity basis, the engine verifies that the resistive voltage drop along the cable run stays within 3 % of the nominal supply voltage — the limit recommended by IEC 60364-8-1 for final circuits. The voltage drop is computed from the conductor resistivity, the CSA, the one-way cable length, and the load current, with an additional √3 factor for three-phase circuits. The pass/fail result and the actual voltage-drop percentage are both shown in the cable schedule.
ΔV₃ = √3 · I_load · L · (ρ / CSA) · cos φwhere ΔV₃ = line-to-line voltage drop (V); I_load = load current (A); L = one-way cable length (m); ρ = conductor resistivity (Ω·mm²/m): 0.0175 for copper, 0.028 for aluminium; CSA = conductor cross-sectional area (mm²); cos φ = power factor (dimensionless)
ΔV₁ = 2 · I_load · L · (ρ / CSA)where ΔV₁ = voltage drop (V); factor 2 accounts for the outgoing and return conductors; other symbols as above. Voltage-drop percentage = (ΔV / V_supply) × 100 %; pass when ≤ 3 %.
Frequently asked questions
Which standard does this electrical schematic editor use?
The symbol library follows IEC 60617 — the international standard for graphical symbols used in electrotechnical diagrams, covering contacts, coils, motors, sensors, transformers and bus systems. The cable-sizing engine applies IEC 60364-5-52 for current-carrying capacity (XLPE and PVC insulation; copper and aluminium conductors) and the 3 % voltage-drop limit from IEC 60364-8-1. Parallel-conductor sizing follows IEC 60364-5-52 §523.2.
Can I draw multi-sheet ladder diagrams?
Yes. The editor supports any number of sheets within a single project. Rungs are numbered per-sheet, and you can add cross-reference tags so a coil on Sheet 1 links to its auxiliary contacts on Sheet 2. Each sheet exports independently or as part of the combined PDF report.
How does the cable-sizing calculator work?
Enter the load current, supply voltage, cable length, number of phases, conductor material (copper or aluminium) and insulation type (XLPE or PVC). The engine selects the minimum conductor CSA whose IEC 60364-5-52 ampacity meets the load, then checks that the resistive voltage drop is within 3 % of the supply voltage. If the load exceeds the maximum single-conductor rating, it recommends the number of parallel conductors required.
What does the exported PDF report include?
The branded PDF contains the full multi-sheet schematic with the IEC 60617 symbol key, the automatic bill of materials (device counts and tag references), and the cable schedule (selected CSA, calculated voltage drop, and pass/fail status for each cable run). Reports are available on a paid plan.
Is the electrical schematic editor free?
You can explore the editor during a free 30-minute preview with no sign-up required. A free 14-day account trial (no credit card) unlocks every tool at Pro level. The branded PDF report, saved schematics and cable schedules are part of a paid Pro plan.
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