# NCEES 533



## colo_elec (Apr 14, 2010)

Ok, So I am lost on this problem. Why do we sum the 3H, and what are we summing, 3A per phase? Anyone have a good read on harmonic calcs?


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## phowardtx (Apr 15, 2010)

colo_elec said:


> Ok, So I am lost on this problem. Why do we sum the 3H, and what are we summing, 3A per phase? Anyone have a good read on harmonic calcs?


Going for the hat trick...and also staying up way too late studying this stuff, but here's a brief summary on harmonics...

http://ecmweb.com/mag/electric_fundamentals_harmonics/

In this case 60-Hz and 60A are useless information. 3rd harmonic phase currents are additive and are the highest in magnitude of the triplen harmonics (3rd, 6th, 9th). Each phase's harmonics contributes to the neutral current.

So here we have 3A of 3rd harmonic per phase so all we do is sum them up.


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## bacchi (Apr 15, 2010)

colo_elec said:


> Ok, So I am lost on this problem. Why do we sum the 3H, and what are we summing, 3A per phase? Anyone have a good read on harmonic calcs?


Third harmonic is a triplen harmonic. Odd harmonics add up in neutral. Harmonic currents are routed through neutral. In this case, harmonic curents in each phase route through neutral therfore current is additive in neutral.

3X 3 = 9amp

Does anyone know what happens in 3 phase three wire systems?


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