Dịch vụ & Phân phốiCâu 45 / 521
What is the full-load secondary current of a 45 kVA, 3-phase, 208 V transformer?
a.216 A
b.125 A
c.108 A
d.94 A
Giải thích
I = 45,000 / (1.732 x 208) = 125 A. The formula uses line-to-line voltage times the square root of 3; the other values drop the sqrt-3 factor or use single-phase math.
Trích dẫn luật: 2023 NEC §450.3Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- The optional feeder/service calculation of 220.84 for a multifamily dwelling may be used only when which condition is met?
- A dwelling has 10 kW of electric heat and a 5 kW air conditioner that never run at the same time. What load is included in the calculation?
- Service-entrance conductors must supply a computed load of 160 A continuous. What minimum conductor ampacity is required per 230.42?
- What is the full-load primary current of a 75 kVA, 3-phase, 480 V transformer?
- For a transformer over 1000 V or with primary-only protection under 450.3(B), where primary current is 9 A or more, the primary OCPD generally may not exceed what percentage of primary full-load current?
- A transformer has a primary full-load current of 40 A and uses primary-only overcurrent protection. What is the maximum standard primary OCPD (125% rule)?
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