Motors & Equipment第 104 / 120 题
What is the maximum non-time-delay fuse permitted for branch-circuit short-circuit and ground-fault protection of a 34-ampere three-phase squirrel-cage motor, using the next standard size allowance?
a.110 amperes
b.100 amperes
c.90 amperes
d.125 amperes
解析
Non-time-delay fuses are permitted at 300 percent of full-load current: 34 x 3.00 = 102 A, which is not a standard rating, so the next standard size of 110 amperes may be used. The 90-ampere answer belongs to the inverse-time breaker at 250 percent, and 125 amperes skips a standard size.
法律依据: 2023 NEC Table 430.52(C)(1)免费刷完整 120 道题库 — 无需注册。
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