Services & DistributionQuestion 104 of 521
A 208Y/120 V, 3-phase feeder supplies a balanced 50 kVA load. The approximate line current (and therefore the minimum conductor ampacity before continuous factors) is:
a.120 A
b.139 A
c.174 A
d.96 A
Explanation
For a 3-phase load, I = VA / (1.732 x line voltage) = 50,000 / (1.732 x 208) = about 139 A. Dividing by voltage alone or using a single-phase formula gives the incorrect answers; the sqrt(3) factor is required for three-phase current.
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