Branch Circuits & Feeders第 6 / 120 题
A 480-volt, three-phase feeder carries 40 amperes 250 feet using 6 AWG copper (26,240 circular mils). Using K = 12.9, what is the approximate voltage drop?
a.14.8 volts
b.4.9 volts
c.8.5 volts
d.17.0 volts
解析
For three-phase, VD = (1.732 x K x I x L) / CM = (1.732 x 12.9 x 40 x 250) / 26,240, or about 8.5 volts, roughly 1.8 percent of 480 volts. The 17.0-volt answer uses the single-phase factor of 2 instead of 1.732, 4.9 volts halves the run length, and 14.8 volts does not follow from the given values.
法律依据: 2023 NEC Chapter 9, Table 8免费刷完整 120 道题库 — 无需注册。
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