Motors & EquipmentQuestion 89 of 120
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.50 amperes
b.40 amperes
c.46 amperes
d.60 amperes
Explanation
The disconnecting means must have an ampere rating of at least 115 percent of the full-load current: 40 x 1.15 = 46 A, so a 60-ampere switch would be the practical selection. The 40-ampere answer omits the 115 percent factor entirely, and 50 or 60 amperes are available equipment ratings rather than the calculated minimum the question asks for.
Law Reference: 2023 NEC §430.110(A)Practice all 120 questions free — no signup required.
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