56 questions
An indoor dry-type transformer rated 45 kVA with standard (Class 105) insulation must maintain what minimum separation from combustible material unless otherwise protected?
- a.18 in
- b.3 in
- c.12 in✓
- d.6 in
2023 NEC 450.21(A): dry-type transformers 112.5 kVA and under must be separated at least 12 in from combustible material unless the unit has a listed fire-resistant barrier or Class 155 (or higher) insulation.
Which value from a motor nameplate must be used with the tables to size branch-circuit short-circuit protection and conductors, per 430.6(A)?
- a.the nameplate full-load amperes
- b.the service-factor amps
- c.the locked-rotor current
- d.the table full-load current, not the nameplate current rating✓
2023 NEC 430.6(A)(1): for general motor applications, the full-load current values in Tables 430.247-430.250 (not the nameplate FLA) are used to size conductors and short-circuit/ground-fault protection. Overload protection uses the nameplate FLA.
The disconnecting means for air-conditioning or refrigerating equipment with a motor-compressor must be located:
- a.only at the main service panel
- b.inside a locked mechanical room only
- c.at least 25 ft away
- d.within sight from and readily accessible from the equipment✓
2023 NEC 440.14: the disconnect must be within sight from, and readily accessible from, the air-conditioning or refrigerating equipment.
How many overload (running-protection) units are required for a three-phase alternating-current motor?
- a.one
- b.three✓
- c.four
- d.two
2023 NEC Table 430.37: a three-phase AC motor requires three overload units, one in each phase.
In patient care spaces, grounding of receptacles and fixed electrical equipment must be accomplished by:
- a.an isolated ground only
- b.the metal raceway alone as the only ground path
- c.the grounded (neutral) conductor
- d.an insulated copper equipment grounding conductor plus a metal raceway or cable armor (redundant ground)✓
2023 NEC 517.13: patient care spaces require redundant grounding - an insulated copper EGC AND a metallic raceway or cable that itself qualifies as a grounding path.
The disconnecting means for a motor must have an ampere rating of at least what percentage of the motor full-load current?
- a.115%✓
- b.125%
- c.100%
- d.110%
2023 NEC 430.110(A): the disconnecting means for a motor circuit must be rated at least 115% of the motor full-load current.
这门考试有多难？
电工技师（Master）执照由各州主办、以 NEC 为依据，因此格式因州而异。例如在德州，考试分两个开卷部分（2023 NEC）——75 道 NEC 知识题与 33 道计算题（共 108 题）——各须 70% 方可通过，费用 78 美元。电工年薪中位数约 62,350 美元（BLS，2024 年 5 月）。
- 推荐学习时间
- 多数人 80-150 小时——技师考试比熟练工增加更重的计算与规范应用深度。
- 官方公布的通过率
- 19.08% （来源未说明统计的是哪些考次）（n = 3,946）；22.21% （来源未说明统计的是哪些考次）（n = 3,472） —— Texas TDLR，FY 2025。请把它们看作两场考试而非一场：TDLR 并没有名为「Master Electrician」的行，只有「Master Calculations」（第一个数字）和「Master NEC」（第二个数字）。任何引用单一「德州 master 通过率 19%」的说法，都悄悄丢掉了一半考试。执照按州发放，因此这只适用于德州。来源： Texas TDLR — Electrician Exam Statistics, Fiscal Year 2025
- 重点学习方向
- 服务、服务设备与单独派生系统是最重的板块之一（德州约 18%），外加负载计算部分。
费用与薪资为近似值，会随时间变动。上方的通过率引自旁边链接的来源，并限于该来源覆盖的期间——凡是我们尚未核实来源的，都会直接说明并且不给数字。