Electrical Exam Prep Unit 7

Front 1

What size conductors are required for a 1 hp, single-phase, 115V motor with terminals rated 75°C?

Back 1

14 AWG

Front 2

What size conductors are required for a 2 HP, single-phase, 230V motor?

Back 2

14 AWG

Front 3

What size conductors are required for a 5 HP, single-phase 208V motor?

Back 3

8 AWG

Front 4

Motors and their associated equipment must be protected against overcurrent (overload, short circuit, or ground fault), but because of the special characteristics of induction motors, overcurrent protection may be generally accomplished by having the overload protection separate from the short-circuit and ground-fault protection.

True or false?

Back 4

True

Front 5

Which parts of Article 430 contains the requirements for motor short-circuit and overload protection?

(a) Motor and branch-circuit overload protection part 3

(b) Motor branch circuit short circuit and ground fault protection part 4

(C) a and b

(d) None of these

Back 5

a and b

Front 6

What's the FLC for a 5 HP, 120V, direct-current motor?

Back 6

40A

Front 7

What's the FLC for a 5 hp, 115V, single-phase motor?

Back 7

56A

Front 8

What's the FLC for a 5 HP, 200V, single-phase motor?

Back 8

32.20A

Front 9

What's the FLC for a 5 HP, 230V, three-phase motor?

Back 9

15.20A

Front 10

What size conductors are required for a 1 hp, single-phase, 115V motor with terminals rated 75°C?

Back 10

14 AWG

Front 11

What size conductors are required for a 2 HP, single-phase, 230V motor?

Back 11

14 AWG

Front 12

What size conductors are required for a 5 HP, single-phase, 208V motor?

Back 12

8 AWG

Front 13

What size conductors are required for a 5 HP, single-phase, 230V motor?

Back 13

8 AWG

Front 14

What size branch-circuit conductors are required for a 5 HP, three-phase, 208V motor with terminals rated 75°C?

Back 14

12 AWG

Front 15

What size branch-circuit conductors are required for a 7 1/2 HP, three-phase, 230V motor?

Back 15

10 AWG

Front 16

What size branch-circuit conductors are required for a 25 hp, three-phase, 460V motor with terminals rated 75°C?

Back 16

8 AWG

Front 17

What size branch-circuit conductors are required for a 7 1/2 HP, three-phase, 230V motor? The nameplate FLA is 20A, rated for 5-minute service, used for intermittent duty, and the terminals are rated 75°C.

Back 17

14 AWG

Front 18

What size branch-circuit conductors are required for a 7 1/2 hp, three-phase, 230V motor? The nameplate FLA is 20A, rated for 30 minute service, and used for short time duty.

Back 18

10 AWG

Front 19

What size feeder conductors are required for a 5 HP and 3 HP, single-phase, 230V motor?

Back 19

6 AWG

Front 20

What size feeder conductors are required for two 7 1/2 HP, three-phase, 230V motors with terminals rated 75°C?

Back 20

8 AWG

Front 21

What size feeder conductors are required for two 7 1/2 HP and one 15 HP, three-phase, 230V motors with terminals rated 75°C?

Back 21

3 AWG

Front 22

Overload is the condition where the current is greater than the equipment rating, resulting in equipment damage due to dangerous overheating [Article 100]. Overload protective devices, sometimes called "heaters" are intended to protect the ______ from dangerous overheating.

Back 22

All of these

Front 23

22. The NEC requires motor overload protection devices to be sized according to the motor full-load current ratings listed in Tables 430.247, 430.248, or 430.250.

True or false?

Back 23

False

Front 24

23. If the motor overload protection relay sized according to 430.32(A)(1) isn't capable of carrying the motor starting and running current, a larger overload can be used if it's sized according to the requirements of 430.32(C).

True or false

Back 24

True

Front 25

24. Motors with a nameplate service factor (SF) rating of 1.15 or more must have the overload protective device sized at no more than _____ percent of the motor nameplate current rating.

Back 25

125

Front 26

25. Motors with a nameplate temperature rise rating not over 40°C must have the overload protective device sized at no more than ______ percent of the motor nameplate current rating.

Back 26

125

Front 27

26. Motors that have a service factor rating of 1.10 must have the overload protective device sized at not more than ______ percent of the motor nameplate ampere rating.

Back 27

115

Front 28

27. If a dual-element time-delay fuse is used for overload protection, what size fuse is required for a 5 HP, 208V, three-phase motor with a service factor of 1.15 and a motor nameplate current rating (FLA) of 16A?

Back 28

20A

Front 29

28. If a dual-element time-delay fuse is used for overload protection, what size fuse is required for a 30 HP, 460V, three-phase synchronous motor, with a nameplate current rating of 32A, and a temperature rise of 39°C?

Back 29

40A

Front 30

30. In addition to overload protection, each motor and it's accessories require branch-circuit short-circuit and ground-fault protection according to 430.52. When sizing the branch-circuit protective device, which of the following factors must be considered?

Back 30

All of these

Front 31

31. The NEC requires motor branch-circuit short-circuit and ground-fault protection to be sized not greater than the percentages listed in Table 430.52. When the branch-circuit short-circuit and ground-fault protective device value determined from Table 430.52 doesn't correspond with the standard rating of overcurrent devices as listed in 240.6(A), the next _____ device size is permitted to be used.

Back 31

Larger

Front 32

32. To determine the percentage of the motor FLC from Table 430.52 that's to be used to size the motor branch-circuit short-circuit and ground-fault protective device, which of the following steps should be used?

Back 32

All of these

Front 33

33. Where the next size up dual-element time-delay fuse isn't sufficient for the starting current of a motor, the rating of the fuse is permitted to be increased but must im no case exceed____ percent of the motor's full-load current.

Back 33

225

Front 34

34. Conductors are sized at _____ percent of the motor full-load current, overloads from _____ percent, and the motor short-circuit and ground-fault protective device (inverse time circuit breaker) is sized up to ______ percent of the motor full-load current.

Back 34

125, 115, 250

Front 35

36. What size conductor and inverse time circuit breaker are required for a 2 HP, 230V, single-phase motor?

Back 35

14 AWG conductor and a 30A breaker

Front 36

37. What size nontime delay fuses are required for a 2 HP, 230V, single-phase motor?

Back 36

40A

Front 37

38. What size dual-element time-delay fuses are required for a 2 HP, 230V, single-phase motor?

Back 37

25A

Front 38

40. What size conductor and inverse time circuit breaker is required for a 5 HP, 208V, single-phase motor?

Back 38

10 AWG conductor and a 60A breaker