FREE TN-LLE Motors and Motor Circuits Questions and Answers

Question 1

What is the minimum ampacity required for the branch-circuit conductors supplying a 10 HP, 230-volt, 3-phase squirrel-cage motor?

Accepted Answer

35A

Answer

28A

Answer

40A

Answer

22.4A

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 10 HP, 230V, 3-phase motor (FLC 28A)?

Accepted Answer

70A

Answer

60A

Answer

40A

Answer

90A

Question 3

A feeder supplies two 3-phase, 230V motors: a 10 HP (FLC 28A) and a 5 HP (FLC 15.2A). What is the minimum required ampacity for the feeder conductors?

Accepted Answer

50.2A

Answer

43.2A

Answer

54A

Answer

65.2A

Question 4

Using the same motors from the previous question (10 HP and 5 HP), what is the maximum standard size inverse-time circuit breaker permitted for the feeder protection?

Accepted Answer

80A

Answer

100A

Answer

90A

Answer

70A

Question 5

What is the maximum setting for a separate overload protection device for a continuous-duty motor with a nameplate FLC of 40A, a service factor of 1.15, and a temperature rise of 40°C?

Accepted Answer

50A

Answer

40A

Answer

46A

Answer

60A

Question 6

A motor control circuit is tapped from the load side of a 60A branch-circuit breaker and the conductors do not leave the enclosure. What is the minimum size copper conductor required for this control circuit?

Accepted Answer

14 AWG

Answer

18 AWG

Answer

16 AWG

Answer

12 AWG