FREE E2 Sizing and Protection of Motor Circuits Questions and Answers

Question 1

What is the minimum ampacity required for the branch-circuit conductors supplying a single 25-hp, 460-volt, 3-phase, continuous-duty motor?

Accepted Answer

42.5 A

Answer

34 A

Answer

51 A

Answer

37.4 A

Question 2

What is the maximum standard size inverse-time circuit breaker that can be used for branch-circuit, short-circuit, and ground-fault protection for a 50-hp, 460-volt, 3-phase motor?

Accepted Answer

175 A

Answer

125 A

Answer

150 A

Answer

200 A

Question 3

A continuous-duty motor has a nameplate current rating of 40A and a service factor of 1.15. What is the maximum rating for a separate overload protection device for this motor?

Accepted Answer

50 A

Answer

40 A

Answer

46 A

Answer

60 A

Question 4

A feeder supplies three motors with FLCs of 50A, 30A, and 15A. What is the minimum required ampacity for the feeder conductors?

Accepted Answer

107.5 A

Answer

95 A

Answer

118.75 A

Answer

142.5 A

Question 5

A feeder supplies two motors. The largest motor is protected by a 150A branch-circuit breaker, and the second motor has an FLC of 40A. What is the maximum size circuit breaker allowed for the feeder protection?

Accepted Answer

175 A

Answer

200 A

Answer

190 A

Answer

225 A

Question 6

The disconnecting means for a motor controller and the motor shall have an ampere rating of at least what percentage of the motor's full-load current?

Accepted Answer

115%

Answer

100%

Answer

125%

Answer

80%