Branch Circuits & Feeders第 15 / 120 题
A four-wire, three-phase, 208Y/120-volt feeder supplies electric-discharge lighting, and the major portion of the load is nonlinear. How many current-carrying conductors are counted for adjustment purposes?
a.Two
b.Four
c.Three
d.Five
解析
When the major portion of the load is nonlinear, harmonic currents keep the neutral loaded even under balanced conditions, so the neutral counts as a current-carrying conductor along with the three phase conductors, giving four. If the load were linear the neutral would not be counted, giving three, and the equipment grounding conductor is never counted.
法律依据: 2023 NEC §310.15(E)免费刷完整 120 道题库 — 无需注册。
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