Compare copper V-75 sizes for current capacity, installation conditions and voltage drop.
Copper V-75 multicore screening using explicit cable construction, ampacity columns and correction factors; simplified Table C8 voltage drop. Aluminium/XLPE sizing is withheld pending verified data. A result is not a certified cable selection.
Results
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Method and assumptions
Copper V-75 screening with two loaded cores for single phase and three for balanced three phase. Governing size considers ampacity (after ambient/grouping/burial/soil/harmonics), volt-drop, and optional adiabatic short-circuit. Confirm against your licensed edition and manufacturer data before use. Wall/conduit grouping assumes bunched, equally loaded circuits; tray means one horizontal perforated row. Partial insulation follows clause 3.4.3; complete insulation covers more than 400 mm along the cable. Underground grouping and parallel runs require a separate assessment.
Base ampacity reference (V-75)
AS/NZS 3008.1.1:2025 Table 3.15 (two loaded cores). Air: 40 °C. Ground: 25 °C, 0.5 m depth, 1.2 K·m/W. These base values precede correction factors and assume no thermal insulation.
Copper V-75 multicore current-carrying capacity from AS/NZS 3008.1.1:2025 Tables 3.15 and 3.18 with the applicable correction factors, voltage drop by AS/NZS 3000 Table C8, and an optional adiabatic short-circuit check. It does not select protective devices or confirm the installation complies.
How does it handle thermal insulation?
It uses the partially or completely surrounded current rating columns rather than a single derating factor. Under clause 3.4.3 of AS/NZS 3008.1.1, completely surrounded means bulk insulation around the cable for more than 400 mm; 150 mm to 400 mm counts as partially surrounded. Shorter covered lengths need installation-specific data.
Does spacing cables on a tray remove the grouping factor?
Not always. The tray option assumes one horizontal row on perforated tray and uses Table 3.35. Three circuits spaced one cable diameter apart still take a 0.98 correction factor. Other tray types, layers or arrangements need their own factors.
What does the short-circuit check assume?
The adiabatic equation S = I√t ÷ K with copper V-75 conductors from 75 °C to 160 °C (K = 111.2) and clearing times up to 5 s. Cable restraint, the protective device’s let-through energy and the actual cable construction need separate checks.
