Cable Sizing — Three Checks, One Governs

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Cable Sizing — three checks, one governs AMPACITY · VOLT DROP · SHORT-CIRCUIT · STARTING DIP

Reference values are INDICATIVE teaching figures. The base ampacities, derating factors and k-values here are indicative, in the style of the IEC 60364-5-52 family. They were reconstructed for illustration and are not transcribed from the standard — they may not match the published table. For any real work use your licensed copy of the standard and the vendor datasheet. Use your project’s cable schedule and the manufacturer’s tables for real sizing.

The load

MOTOR RATING SYSTEM VOLTAGE

POWER FACTOR (running) STARTING METHOD

The route

ROUTE LENGTH INSTALLATION METHOD

AMBIENT AIR TEMPERATURE CABLES GROUPED TOGETHER CABLE CONSTRUCTION

Fault & limits

PROSPECTIVE FAULT CURRENT PROTECTION CLEARING TIME VOLT-DROP LIMIT, RUNNING VOLT-DROP LIMIT, STARTING

Realistic presets

The three checks (four, on a motor)

1 · Ampacity

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3 · Short-circuit

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2a · Volt drop (run)

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2b · Volt drop (start)

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RUNNING VOLT DROP

STARTING DIP AT MOTOR TERMINALS

DERATED CAPACITY USED (Ib / Iz)

Size-by-size, at this length

mm²	Iz A	ΔV run	ΔV start	SC ok

swipe sideways, or tap a tab

Educational teaching tool — simplified and illustrative. Not for engineering design use.