S = b·ρ·L·I·cos φ / (ΔUmax − b·L·I·x·sin φ) — b = 2 (DC, 1~), √3 (3~)

S = n·ρ·L·I² / Pmax — n = 2 (DC, 1~), 3 (3~)

S = (I²·ρ(θmax) / (2·√π·h·ΔT·10⁻³))^(2/3), ΔT = θmax − θcalc.

S = Isc·√t / k —

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