Thiết bị & Hệ thốngCâu 246 / 521
Using the same 20 HP, 460 V motor (FLC 27 A), what is the maximum dual-element (time-delay) fuse permitted by Table 430.52 for branch-circuit short-circuit and ground-fault protection?
a.67.5 A
b.47.25 A
c.81 A
d.33.75 A
Giải thích
Table 430.52 permits a dual-element time-delay fuse at 175% of FLC: 27 x 1.75 = 47.25 A. 67.5 A is 250% (inverse-time breaker), 81 A is 300% (nontime-delay fuse), and 33.75 A is 125%.
Trích dẫn luật: 2023 NEC §430.52Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- A single continuous-duty 25 HP, 460 V, three-phase motor has an FLC of 34 A (Table 430.250). What minimum conductor ampacity is required for its branch circuit?
- A motor's nameplate shows a full-load current of 40 A and a service factor of 1.15. Under NEC 430.32(A)(1), what is the maximum overload device rating at 125% of nameplate FLA?
- For a 20 HP, 460 V, three-phase motor (FLC 27 A), what is the maximum inverse-time circuit breaker rating for branch-circuit short-circuit and ground-fault protection, using the 250% value of Table 430.52?
- A 5 HP, 230 V, three-phase motor has an FLC of 15.2 A. What is the maximum nontime-delay fuse permitted by Table 430.52 for branch-circuit protection?
- For the same 5 HP, 230 V motor (FLC 15.2 A), what is the maximum instantaneous-trip circuit breaker setting permitted by Table 430.52?
- When sizing branch-circuit conductors and short-circuit/ground-fault protection for a standard motor, which current value does the NEC require you to use?
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