430 Qs

In an alternating-current system, the size of the grounding electrode conductor to a concrete-encased electrode isn't required to be larger than a(an) _____ copper conductor.

4 AWG

What size secondary conductor can be used for a three-phase, 480V transformer, where the secondary overcurrent protection is sized at 110A?

4 AWG

If an inverse time breaker is used for the feeder short-circuit protection, what size protection is required for the following 460V, three-phase motors?Motor 1 = 40 hp, 52 FLCMotor 2 = 20 hp, 27 FLCMotor 3 = 10 hp, 14 FLCMotor 4 = 5 hp, 7.60 FLC

175A

What size THHN feeder conductor is required for one 50 hp motor, one 20 hp motor, and two 10 hp motors where all of them are rated 480V, three-phase, with terminals rated 75°C?

1/0 AWG

Feeder conductors supplying fire pump motors and accessory equipment shall be sized no less than _____ percent of the sum of the fire pump motor(s) and pressure maintenance motor(s) full-load currents, plus 100 percent of the ampere rating of the fire pump accessory equipment.

125

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.

125

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

14 AWG conductor and a 30A breaker

According to Table 430.250, what's the FLC for a 5 hp, 230V, three-phase motor?

15.20A

What's the required feeder short-circuit and ground-fault protection (inverse time circuit breaker) for two 40A motors, one 20A (15-minute duty cycle) motor, and one 7A motor?

150A

The feeder protection for one 25 hp, 208V, three-phase motor, and three 3 hp, 120V, single-phase motors will be ______ after balancing.Note: Use inverse time breakers.

225A

What's the input VA of a 3 hp, 208V, single-phase motor?

3,890 VA

What size overcurrent device is required for a 25 hp, 208V, three-phase fire pump motor with a locked rotor current of 404A?

450A

According to Table 430.248, what's the FLC for a 5 hp, 115V, single-phase motor?

56A

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

6 AWG

A 2 hp, 120V, single-phase motor requires a ______ branch-circuit short-circuit and ground-fault protective device. Note: Use an inverse time breaker.

60A

What's the maximum primary overcurrent device rating for a 2.50 kVA, 480V, single-phase transformer?

6A

The branch-circuit short-circuit and ground-fault protection (circuit breaker) for a 125 hp, 240V, direct- current motor is _____. Note: Use an inverse time breaker.

700A

What's the maximum primary overcurrent device rating for a 25 kVA continuously loaded, three-phase, 240V transformer?

80A

What size conductor and short-circuit and ground-fault protective device is required for a multimotor hermetic refrigerant motor-compressor air conditioner? The nameplate minimum circuit ampacity is 22.10A, the maximum circuit breaker amperes are 35A, and the terminals are rated 60°C.

80A breaker

What size feeder protection is required for the following two motors?Motor 1; 10 hp, 460V, three-phase: FLC = 14A [Table 430.250]. Motor 2; 20 hp, 460V, three-phase: FLC= 27A [Table 430.250].

80A breaker

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

False

For general motor applications, the motor branch-circuit short-circuit and ground-fault protection device shall be sized based on the _____ values.

NEC table

Circuit conductors on the output of an adjustable-speed drive system are susceptible to breakdown under certain conditions due to the characteristics of the output waveform of the drive.

True

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

Overload devices are intended to protect motors, motor control apparatus, and motor branch-circuit conductors against _____.

excessive heating due to motor overloads and excessive heating due to failure to start

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), _____ device size is permitted to be used.

the next larger

What size conductor and inverse time circuit breaker is required for a 7½ hp, 230V, three-phase motor?

10 AWG conductor and a 60A breaker

What's the VA load for the following five motors: 2 hp at 120V; 3 hp at 208V, single-phase; 5 hp at 208V, three-phase; 30 hp at 480V, three-phase; and 50 hp at 480V, three-phase?

100,079 VA

The primary overcurrent protection for a transformer rated 1,000V, nominal, or less, having a primary current rating of 9A or more must be set at not more than _____ percent of the primary current when using primary only overcurrent protection.

125

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.

125, 115, 250

The maximum size overcurrent device for primary only protection of a three-phase, 112.50 kVA transformer with a 480V primary and a 120/208V secondary is _____.

175A

A 75 kVA, 480V primary to 120/208V secondary, three-phase transformer with a 125A primary overcurrent device will require at least _____primary conductors with terminals rated 75°C.

2 AWG

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

8 AWG

What size secondary conductor can be used for a three-phase, 480V transformer, where the secondary overcurrent protection is sized at 50A with terminals rated 75°C?

8 AWG

What's the maximum primary overcurrent device rating for a 25 kVA continuously loaded, three-phase, 240V transformer?

80 A

There are three motors; one 5 hp, 230V, single-phase motor with a service factor of 1.20; and two 1½ hp, 120V, single-phase motors. Using an inverse time breaker, the 3-wire feeder conductor protective device after balancing all three motors will be _____.

90A

What size feeder protection is required for the following two motors?Motor 1; 5 hp, 230V, single-phase: FLC = 28A [Table 430.248]. Motor 2; 2 hp, 230V, single-phase: FLC= 12A [Table 430.248].

80A breaker

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.

115

What size conductor and short-circuit and ground-fault protective device is required for a multimotor hermetic refrigerant motor-compressor air conditioner? The nameplate minimum circuit ampacity is 30.10A, and the maximum circuit breaker amperes are 50A.

10 AWG conductor and a 50A breaker

What size branch-circuit conductors are required for a 7½ 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.

14 AWG

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

14 AWG

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

14 AWG

The branch-circuit short-circuit and ground-fault protective device for a 10 hp, 230V, single-phase motor must not exceed _____.Note: Use an inverse time breaker.

125A

The maximum size overcurrent device for primary only protection of a three-phase, 75 kVA transformer with a 480V primary and a 120/208V secondary is _____.

125A

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 in no case exceed _____ percent of the motor's full-load current.

225

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

8 AWG

What size feeder conductors are required for two 7½ hp, three-phase, 230V motors with terminals rated 75°C?

8 AWG

What's the maximum primary overcurrent device rating for a 0.50 kVA, single-phase, 240V transformer?

3 A

What size conductor is required for a 25 hp, 208V, three-phase fire pump motor with terminals rated 75°C?

3 AWG

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

What size THW conductor is required for a 5 hp, 230V, single-phase motor with terminals rated 75°C?

10 AWG

What size branch-circuit conductors are required for a 7½ hp, three-phase, 230V motor?

10 AWG

What size branch-circuit conductors are required for a 7½ hp, three-phase, 230V motor? The nameplate FLA is 20A, rated for 30-minute service, and used for short-time duty.

10 AWG

Which part(s) of Article 430 contains the requirements for motor short-circuit and overload protection?

10 AWG conductor and a 35A breaker

What's the required feeder conductor for one 50 hp (5-minute varying duty) motor, one 10 hp motor, and two 5 hp motors where all of them are rated 480V, three-phase, with terminals rated 75°C?

2 AWG

The branch-circuit conductors of a 5 hp, 230V, single-phase motor with a nameplate rating of 25A must have an ampacity of not less than _____.Note: This 5 hp motor is used for intermittent duty and, due to the nature of the apparatus it drives, it can't run for more than 5 minutes at any one time.

22A

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.

all of these

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?

all of these

Which of the following statements about a 30 hp, 460V, three-phase synchronous motor and a 10 hp, 460V, three-phase motor is(are) true?

all of these

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

12 AWG

Overcurrent protection for the secondary of a transformer rated 1,000V or less having a secondary current rating of 9A or more must be set at not more than _____ percent of the secondary current rating.

125

The standard overload protective device for a 2 hp, 115V motor with a full-load current rating of 24A and a nameplate rating of 21.50A must not exceed _____.

24.70A

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

25A

In addition to overload protection, each motor and its 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?

all of these

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

40A

What's the FLC from the NEC Tables [Table 430.247] for a 5 hp, 120V direct-current motor?

40A

Motor feeder conductors for more than one motor (sized according to 430.24) must have a feeder protective device to protect against short circuits and ground faults (not overloads) sized not greater than the _____.

largest branch-circuit short-circuit and ground-fault protective device of any motor of the group [430.52] plus the sum of the full-load currents of the other motors on the same phase