Three-Phase Neutral Current
Unbalanced neutral current from the phasor sum of three 120-degree-displaced phase currents, with a triplen-harmonic neutral estimate and a neutral-as-CCC advisory.
Formula and source
I_N = sqrt(Ia^2 + Ib^2 + Ic^2 - Ia*Ib - Ib*Ic - Ic*Ia), the RMS magnitude of the phasor sum of three 120-degree-displaced phase currents. A balanced linear load gives I_N = 0; with dominant triplen (3rd-harmonic) content the neutral approaches 3 x the per-phase triplen current and can exceed the phase current.
Phasor-sum first principles; neutral-as-current-carrying-conductor and harmonic guidance per NEC Article 310 and IEEE Std 519, by name.
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