Transformer K-Factor From the Harmonic Spectrum (UL 1561)
Computes the transformer K-factor from a measured harmonic current spectrum, K = sum(Ih^2 x h^2) / sum(Ih^2) with the harmonics entered as per-unit of the fundamental (UL 1561 / IEEE C57.110), then rounds up to the next standard K-rating (K-1 standard, then K-4 / K-9 / K-13 / K-20 / K-30 / K-40). The measured spectrum and the manufacturer govern.
Formula and source
K = sum(Ih^2 x h^2) / sum(Ih^2) over h = 1,3,5,7,9,11,13 with harmonics in per-unit of the fundamental; round up to the next standard K-rating (K-1, K-4, K-9, K-13, K-20, K-30, K-40).
Transformer K-factor for nonlinear loads, UL 1561 and IEEE C57.110, by name.
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