Three-Phase Neutral Current
Unbalanced neutral current from the phasor sum of three 120-degree-displaced phase currents.
Example
You enter
- Phase A current (A) 100
- Phase B current (A) 80
- Phase C current (A) 60
You get
- Neutral current 34.64 A
- Max phase (A) 100
Details, formula, and sources
With a triplen-harmonic neutral estimate and a neutral-as-CCC advisory.
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.
NFPA 70 free read-only at nfpa.org/freeaccess; IEEE 519 is the named harmonic-limits standard.
Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
Field names used by the API: ia_A, ib_A, ic_A, neutral_A, max_phase_A
- Sinusoidal fundamental the phasor-sum form assumes the fundamental; harmonic content is handled by the separate triplen estimateAC circuit theory