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Neutral Conductor Size with Harmonic Loading

Estimate neutral RMS duty from fundamental imbalance and aligned third-harmonic current, then compare it with corrected neutral capacity.

Inputs

Project inputs and assumptions

Range: 0–100,000 A

Enter the representative fundamental phase-current magnitude.

Range: 0–100 %

Enter the estimated residual fundamental neutral component as a percentage of the representative phase current; this is not phase-current imbalance by itself unless that is how the project data was derived.

Range: 0–500 %

Enter the measured or design third-harmonic RMS component per phase as a percentage of the representative phase current.

Range: 0.01–100,000 A

Enter the reference neutral ampacity before the entered grouping, ambient or installation correction.

Range: 0.01–2

Enter the combined neutral correction factor used by the project basis; do not double-apply a factor already included in the reference capacity.

Result

Neutral capacity margin (A)
0.90
Combined modeled neutral RMS (A)
62.10
Corrected neutral capacity (A)
63.00
Fundamental neutral component (A)
16.00
Third-harmonic neutral component (A)
60.00
Result
The corrected neutral capacity covers the modeled neutral RMS duty for this simplified comparison. Confirm harmonic spectrum, phase arrangement, temperature basis and the applicable Australian requirements separately.

Formula

Calculation logic

Formula definitions and substituted values.

Before relying on the result

  • Screen a neutral serving office or LED loads with triplen harmonics
  • Compare harmonic neutral duty with a derated conductor capacity
  • Use measured harmonic data, phase arrangement, transformer connection and the applicable neutral-sizing rules; this is a simplified model of aligned third harmonics.

Related calculators

Use measured harmonic data, phase arrangement, transformer connection and the applicable neutral-sizing rules; this is a simplified model of aligned third harmonics.