Motors & EquipmentCâu 88 / 120
A 5-horsepower, 230-volt single-phase motor has a table full-load current of 28 amperes. What is the minimum copper branch-circuit conductor at 75 degrees C terminations?
a.10 AWG
b.12 AWG
c.8 AWG
d.6 AWG
Giải thích
The conductor must carry 28 x 1.25 = 35 A. In the 75 degrees C column, 10 AWG copper is exactly 35 A and qualifies, while 12 AWG at 25 A does not. Note that 240.4(D) limits ordinary 10 AWG circuits to a 30-ampere device, but motor branch-circuit protection is sized under Article 430 instead.
Trích dẫn luật: 2023 NEC §430.22Luyện miễn phí toàn bộ 120 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- That same motor has a nameplate full-load current of 32 amperes and a marked service factor of 1.15. What is the maximum separate overload device rating?
- For that 34-ampere three-phase squirrel-cage motor, what is the maximum inverse-time circuit breaker permitted for branch-circuit short-circuit and ground-fault protection, using the next standard size allowance?
- For the same 34-ampere motor, what is the maximum dual-element time-delay fuse permitted at the standard percentage?
- A 30-horsepower, 460-volt three-phase motor has a table full-load current of 40 amperes. What is the minimum ampere rating of the disconnecting means?
- A feeder supplies a 25-horsepower motor (34 amperes) and a 10-horsepower motor (14 amperes), both 460 volts three phase. What minimum conductor ampacity is required?
- For that same two-motor feeder, if the largest branch-circuit protective device is 90 amperes, what is the maximum feeder overcurrent device rating?
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