Dịch vụ & Phân phốiCâu 102 / 521
A 75 kVA, 208Y/120 V transformer has an impedance of 2%. Using the infinite-bus (worst-case) method, the approximate available fault current at the transformer secondary is about:
a.10,400 A
b.4,160 A
c.20,800 A
d.2,080 A
Giải thích
Secondary full-load current = 75,000 / (1.732 x 208) = 208 A; dividing by the per-unit impedance gives 208 / 0.02 = 10,400 A. Using the wrong impedance or forgetting to divide gives the incorrect values; this infinite-bus method assumes an unlimited primary source.
Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- Where the grounding electrode conductor connects to a concrete-encased electrode, that portion of the conductor is not required to be larger than:
- Where the grounding electrode conductor connects to a made rod, pipe, or plate electrode, that portion of the conductor is not required to be larger than:
- For a feeder/service neutral, the portion of the maximum unbalanced load that exceeds 200 A may generally be calculated at:
- When circuit conductors are run in parallel in multiple raceways, the equipment grounding conductor in each raceway must be:
- 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:
- For a 200 A service where the equipment and conductors are all rated for it, the conductor ampacity used for termination sizing is normally based on which temperature column?
Cập nhật gần nhất: · quy trình kiểm tra
Đội Ngũ Biên Tập PrepPass · Đối chiếu với California CSLB C-10 Electrical Trade Examination · Quy trình kiểm tra