Motors
B. 455.9
JFE-22. Given: A 240 volt, wye-connected motor derives power from a converted single-phase source. It is desired to connect a 120/240-volt transformer for control of the motor on the load side of the converter. The control transformer must _______________. A. be connected to the manufactured phase B. not be connected to the manufactured phase. C. have separated overcurrent protection. D. be disconnected after start-up of the motor.
B. 3 Phase Current Formula (75kW x 1000) / (208 x 1.732) = 208.18 amperes
PE12-21. What is the full-load current rating on the secondary side of a 75kVA, three-phase transformer having a 277/480 volt, primary and a 208Y/120 volt secondary? A. 156 amperes B. 208 amperes C. 360 amperes D. 362 amperes
C. Tbl 430.250 430.24 10 HP FLC = 30.8 amps x 125% = 38.5 amperes 7 1/2 HP FLC = 24.2 amps x 100% = 24.2 amperes Total = 62.7 amperes
PE13-23. Given: a feeder is to supply two (2) continuous-duty, induction type, Design B, 208-volt, three-phase AC motors, one 10 hp and one 7 1/2 hp; the feeder shall have a MINIMUM ampacity of ______. A. 55.00 amperes B. 68.75 amperes C. 62.70 amperes D. 38.50 amperes
B. Tbl. 450.3(B) 25,000 / (208 x 1.732) = 69.3 amps x 125% = 86.62 amps
PE14-19. Given: a three-phase, 25 kVA rated transformer with a 480-volt primary and a 208Y/120-volt secondary is to be installed. Where primary and secondary protection is required to be provided, what is the MAXIMUM standard ampere rating of secondary overcurrent protection permitted by the NEC? A. 80 Amps B. 90 Amps C. 100 Amps D. 110 Amps
B. Tbl 430.250
PE7-9. A 208-volt, 3-phase, 50 HP, squirrel-cage, continuous duty, Design C, AC motor has a full-load running current of ____________. A. 130 Amperes B. 143 Amperes C. 162 Amperes D. 195 Amperes
B. Tbl. 430.52, Note 1
PE9-12. When sizing time-delay Class CC fused for motor branch-circuit, short-circuit, and ground fault protection, they are to be sized at the same value as _______. A. inverse-time circuit breakers B. non-time-delay fuses C. instantaneous trip circuit breakers D. adjustable trip circuit breakers
D. 215.2(A)(1) 430.33 430.22 39 amps + 24 amps = 63 amps x 125% = 78.75 amps
PE12-17. Where exceptions are not to be taken into consideration, where a feeder supplies a continuous lighting load of 39 amperes and a motor load of 24 amperes, the feeder must have an ampacity of at LEAST _________. A. 63 amperes B. 69 amperes C. 73 amperes D. 79 amperes
A. 430.22(E) Tbl. 430.22(E) 18 Amperes x 85% = 15.3 Amperes Note: When sizing conductors for intermittent duty motors, the motor NAMEPLATE rating shall be used.
MFE-12. Determine the MINIMUM required ampacity of the conductors supplying an elevator motor given the following related information: -5HP, 208 volts, three-phase, wound rotor -15 minute rated -nameplate current rating is 18 amperes A. 15.3 Amperes B. 16.2 Amperes C. 18.0 Amperes D. 22.5 Amperes
A. Tbl. 430.52 430.52(C)(1), Ex. 1
JFE-1. When determining the initial standard size time-delay fuse for a branch-circuit, short-circuit, and ground fault protection for a three-phase, continuous duty, squirrel cage, AC motor, the fuse shall have a rating of ______ of the FLC of the motor. When the value determined does not correspond to a standard ampere rating, the next higher standard rating shall be permitted. A. 175 percent B. 150 percent C. 225 percent D. 250 percent
C. 430.72(B)(2) Tbl. 430.72. Col B
JFE-23. What is the MAXIMUM size overcurrent protection device required to protect size 14 AWG conductors used for the pump motor control-circuit that is protected by the motor branch circuit protection device and extends beyond the enclosure? A. 15 Amperes B. 20 Amperes C. 45 Amperes D. 100 Amperes
A. Tbl 430.250 430.24(1) & (2) Tbl. 310.15(B)(16) 15 HP = 42 amps x 125% = 52.5 amps 7 1/2 HP = 22 ams x 100% = 22 amps 3 HP = 9.6 amps x 100% = 9.6 amps Total = 84.1 amps Note: Size 4 THWN conductors with an ampacity of 85 amps should be selected.
PE18-14. What MINIMUM size 75 C copper conductors are required to supply the following listed 3-phase, 230=volt motors? *one(1) 15 hp wound-rotor *one(1) 7 1/2 induction-type *one(1) 3 hp induction-type A. 4 AWG THWN B. 4 AWG THHN C. 3 AWG THW D. 2 AWG THW
C. 430.24(1) & (2)
JFE-24. Branch-circuits supplying more than one motor shall have an ampacity of at LEAST _______ percent of the full-load current of the largest motor, and 100 percent of the FLC of the other motor(s) in the group. A. 100 B. 115 C. 125 D. 150
C. Trade Knowledge
PE2-6. A motor with nine leads coming out of it is a _______. A. two-phase motor B. two-speed motor C. dual-voltage motor D. multi-speed motor
C. 430.110(A)
JFE-65. When an inverse-time circuit breaker is installed only as a disconnecting means of a single continuous-duty motor, the circuit breaker must have an ampere rating of at LEAST ______ of the full-load running current of the motor. A. 100 percent B. 125 percent C. 115 percent D. 150 percent
D. 430.72(B)(2) Tbl. 430.72(B)
PE13-9. Determine the MAXIMUM overcurrent protection permitted for size 14 AWG THWN copper motor control circuit conductors tapped from the load side of a motor overcurrent protection device. Given: The conductors require short-circuit protection and do not extend beyond motor control equipment encolsure. A. 20 amperes B. 25 amperes C. 30 amperes D. 100 amperes
B. 440.22(A)
PE18-18. The branch-circuit, short-circuit, and ground-fault protection for a hermetic motor-compressor shall have a rating or setting NOT exceeding _________ of the motor-compressor rated-load current or branch-circuit selection, whichever is greater, where the protection specified is sufficient for the starting current of the motor. A. 150 percent B. 175 percent C. 125 percent D. 225 percent.
B. 430.110(B)(2) Ex
PE9-19. If a circuit breaker serves as the controller for a motor and the motor is not in sight of the circuit breaker, the NEC requires which of the following? A. the motor to be less than 2 HP B. the breaker be able to be locked in the open position C. the motor to be Code letter "E" D. the breaker to be rated 25,000 AIC
C. 430.22(A) Tbl. 310.15(B)(16) FLC of motor = 70 amps x 125% = 87.5 amps Size 3 AWG THW conductors with an ampacity of 100 amps should be selected.
PE7-7. Determine the MINIMUM size THW copper branch-circuit conductors required by the NEC to supply a 3-phase, continuous duty, AC motor that has full-load current of 70 amperes. Assume all terminations to be rated at 75 C. A. 1 AWG B. 2 AWG C. 3 AWG D. 4 AWG
C. 240.4(B)(2) & (3) 240.6(A)
PE7-8. Given: You determined a conductor has a computed allowable ampacity of 75 amperes. What is the MAXIMUM standard ampere rating of the overcurrent protection device the NEC permits to protect this circuit? This is not a motor circuit or part of the multi-outlet branch-circuit supplying more than one receptacle. A. 70 Amperes B. 75 Amperes C. 80 Amperes D. 85 Amperes
A. 430.75(A)
PE8-1. In general, motor control circuits shall be arranged so that they will be disconnected from all sources of supply when _________. A. the disconnecting means is in the open position. B. the disconnecting means is not within sight of the controller. C. the disconnecting means is integral with the controller. D. installed in a motor control center.
D. 430.6(A)(1)
PE8-9. When determining the required ampacity of the branch-circuit conductors to supply an AC three-phase, continuous-duty motor current values of the motor given on _______ shall be used. A. the motors nameplate value. B. Table 430.248 of the NEC. C. Table 430.520 of the NEC. D. Table 430.250 of the NEC.
D. 430.24
PE9-17. In general, branch-circuit conductors supplying more than one motor shall have an ampacity of at LEAST ______ percent of the FLC of the largest motor, and 100 percent of the FLC of the other motor(s) in the group. A. 25 B. 80 C. 100 D. 125
A. Tbl. 250.122
PE9-18. What is the MINIMUM size equipment grounding conductor required for a 5 HP, 3-phase, 208-volt motor having 20-amperes rated overload protection and short-circuit overcurrent protection rated at 30 amperes? A. 10 AWG B. 14 AWG C. 12 AWG D. 8 AWG
B. 250.178
JFE-30. The MINIMUM size copper conductor that may be used for grounding the secondary of an instrument transformer is; A. 10 AWG B. 12 AWG C. 8 AWG D. 6 AWG
D. 725.48(B)(1) 300.3(C)(1)
JFE-32. Control-circuit conductors and motor branch-circuit conductors are permitted by the NEC to occupy the same raceway if the control-circuit conductors ____________. A. have an applied voltage not exceeding 24 volts. B. have a voltage to ground not to exceed 150 volts. C. have a voltage to ground not to exceed 277 volts. D. are functionally associated with the motor system.
B. 440.52(A)(3)
JFE-85. Where a fuse or inverse time circuit breaker is used for overload protection for a hermetic motor-compressor, this device shall be rated at NOT more then _______ of the motor-compressor rated load-current. A. 115 percent B. 125 percent C. 150 percent D. 175 percent
B. VA=416amp x 208volts * 1.732=149,866VA
MFE-2. Given: A commercial building is to be supplied from a transformer having a 480Y/277-volt, three-phase primary and a 208Y/120-volt, three-phase secondary. The secondary will have a balanced computed demand load of 416 amps per phase. The transformer is required to have a MINIMUM KVA rating of _____? A. 100kVA B. 150kVA C. 86kVA D. 200kVA
A. 430.6(A)(2) 430.32(A)(1) FLA of motor = 18 amps x 115% = 20.7 amps
PE16-17. Determine the MINMUM size overload protection required for a 480-volt, three-phase, 15 HP, continuous-duty AC motor when given the following conditions; *Design B *temperature rise - 40 c *service factor - 1.12 *actual nameplate current rating - 18 ams A. 20.7 Amps B. 18 Amps C. 22.5 Amps D. 23.4 Amps
B. 450.3(B) Tbl. 450.3(B) 240.6(A) 50,000 / (480 x 1.732) = 60.2 amps
PE16-19. Given: A 50kVA transformer has a 480-volt, three-phase primary and a 208Y/120-volt, three-phase secondary. Overcurrent protection is required on both the primary and secondary side of the transformer. Determine the MAXIMUM standard size overcurrent protection device permitted on the primary side. A. 125 amps B. 150 amps C. 175 amps D. 200 amps
D. 695.5(B) Tbl. 430.251(B) 240.6(A) Note: The fire pump motor circuit protective device must be sized to carry indefinitely the locked-rotor current of the motor. According to Tbl. 430.251(B), the locked-=rotor current of the motor is 404 Amperes. the next standard size overcurrent protective device with a rating of 450 Amperes should be selected.
MFE-50. Refer to the previous question. Determine the MAXIMUM standard size overcurrent protection device the NEC permits to protect the fire pump motor. A. 200 Amperes B. 250 Amperes C. 350 Amperes D. 450 Amperes
C. 430.6(A)(1) Tbl. 430. 248 430.22(A) FLC of 7 1/2 HP motor = 40 amps x 125% = 50 amps
P1-18. A branch-circuit supplying a 7 1/2 HP, 240-volt, single-phase, induction-type, continuous duty, Design B, AC motor shall have an ampacity of at LEAST _________ amperes. A. 60 B. 40 C. 50 D. 75
A. 430.110(A) Tbl.430.250 FLC of motor = 34 amps x 115% = 39.1 amps
PE12-13. In general, a general-use fused switch used as a disconnecting means for a 25 HP, 480-volt, three-phase ac motor with a FLA of 32 amperes indicated on the nameplate, must have an ampere rating of at LEAST ________. A. 39 amperes B. 50 amperes C. 56 amperes D. 79 amperes
D. Tbl 110.28
PE15-14. an outdoor motor started (controller) enclosure subject to temporary submersion shall be on an enclosure ________. A. Type 3RX B. Type 3SX C. Type 4X D. Type 6P
A. 430.82(A)
MFE-52. Each motor controller shall be capable of __________and___________ the motor if controls. A. Starting, Stopping B. Starting, Running C. Stopping, Disconnecting D. Stopping, Interrupting
D. 430.102(B) Ex (a) & (b)
MFE-4. Which of the following installations would NOT require a disconnect within sight of the motor if the motor and motor controller are NOT within sight of each other? A. The disconnect is capable of being locked in the OPEN position. B. The disconnecting means is impractical or introduces additional hazards. C. Industrial installations with written safety procedures, and maintained by qualified personnel. D. All of these apply.
B. 430.6(A)(2) 430.32(A)(1) FLC of motor = 78.8 amp x 115% = 86.08 amp
PE17-6. Determine the MAXIMUM setting permitted for the overload protection devices used to protect a 25 hp, 208-volt, 3=phase, continuous-duty, induction-type motor with a temperature rise of 50 c and a FLA rating of 78.8 amps indicated on the nameplate. (Assume the setting you select will be sufficient to start the motor and modification of this value is not necessary). A. 74.8 amps B. 86.02 amps C. 93.5 amps D. 97.24 amps
D. 450.11
JFE-94. Which of the following is NOT required to be marked on the nameplate of a transformer? A. kVA rating B. manufacturer C. voltage D. overcurrent protection
C. Tbl. 430.250 430.24(1) & (2) 10 HP - FLC = 30.8 amps x 125% = 38.5 amps 7 1/2 HP - FLC = 24.2 amps x 100% = 24.2 amps Total = 62.7 amps
JFE-34. A feeder supplying two (2) continuous-duty, 208-volt, three-phase AC motors, one rated 10 HP and one rated 7 1/2 HP shall have an ampacity of at LEAST ______. A. 55.0 Amperes B. 68.75 Amperes C. 62.70 Amperes D. 38.50 Amperes
D. 430.32(C) FLA of motor = 18 amps x 130% = 23.4 amps
PE16-18. Consider the overload protection you have selected on the above motor is not sufficient to start the motor and trips and modification of this value are necessary; determine the MAXIMUM size overload protection permitted A. 22.5 amps B. 20.7 amps C. 25.2 amps d. 23.4 amps
A. 430.242(3)
PE18-19. Where stationary motors are locate din Class I, Zone 2 locations _______. A. the motor frames shall be grounded B. the motor frames shall not be grounded C. the motor rotor shall be grounded D. the motor frames shall be isolated.
D. 3-phase current formula 100,000 / (480 x 1.732) = 120.2 amps
PE17-15. Determine: the full-load current rating of a 100 hp, 480-volt, 3-phase, AC motor. Assume 1,000 watts per hp, because the motor is not rated at 100 percent efficiency. A. 400 amps B. 200 amps C. 125 amps D. 120 amps
D. Tbl. 430.40
PE18-13. Overload relays and other devices for motor overload protection that are not capable of opening short circuits or ground faults shall be protected by a motor short-circuit protector or by _______. A. Class CC fuses only B. an instantaneous trip circuit breaker only C. a ground-fault circuit-interrupter D. fuses or circuit breakers
B. 450.5(A)(2) FLC = 200 amps x 125% = 250 amps
PE18-20. Given: A ground autotransformer will be used to create a 3-phase, 4-wire system from a 3-phase, 3-wire ungrounded system. the full-load current on the autotransformer will be 200 aps. The overcurrent sensing device that will cause the main switch to pen when excessive current occurs, should be set to trip at the MAXMIMUM value of ________. A. 225 amps B. 250 amps C. 300 amps D. 200 amps
C. 430.6(A)(2)
PE2-13. For continuous-duty motors, the motor nameplate current rating is used to determine the size of the ______ required for the motor. A. Disconnecting means B. Branch-circuit conductors C. motor overload protection D. short-circuit protection
A. General Knowledge
PE2-14. In general, branch-circuit conductors that supply a single AC motor used in a continuous-duty application shall have an ampacity of NOT less than ________ percent of the motor's full load running current rating. A. 125 B. 100 C. 150 d. 115
C. Tbl. 430.250 Tbl. 430.52 430.52(C)(1), Ex 1 FLC of motor = 4.6 amps x 300% = 13.8 amps Note: The next standard size fuses with a rating of 15 amps should be selected.
PE9-3. The MAXMIMUM standard rating of the initial non-time-delay fuse for the branch-circuit, short-circuit, and ground-fault-protection of a 1HP, three-phase, 208-volt, squirrel-cage AC motor shall be ________ amperes. A. 6 B. 10 C. 15 D. 20
B. Three-Phase Current Formula 450.3(B) Tbl. 450.3(B) 240.6(A) Primary: (150x1000) / (480 x 1.732) = 180 amps x 250% = 450 Amperes Secondary: (150x1000)/(208x1.732) = 416 amps x 125% = 520 Amperes
MFE-39. Determine the MAXMIMUM standard size overcurrent protection required oft the primary and secondary side of a transformer, when primary and secondary overcurrent protection is to be provided, given the following related information; -150 kVA rating -Primary - 480 volt, three-phase, 3-wire -Secondary - 208Y/120 volt, three-phase, 4-wire A. Primary - 500 Amperes, Secondary - 500 Amperes B. Primary - 450 Amperes, Secondary - 600 Amperes C. Primary - 500 Amperes, Secondary - 450 Amperes D. Primary - 450 Amperes, Secondary - 500 Amperes
D. Tbl. 430.248
P1-8. The full-load running current of a 3-HP, 208-volt, single phase continuous duty AC motor is _____________. A. 10.6 Amperes B. 19.6 Amperes C. 13.2 Amperes D. 18.7 Amperes
B. Tbl. 430.250 695.6(B)(2) 430.22 Tbl. 310.15(B)(16) FLC of 25hp, 208 volt motor = 74.8 Amperes x 125% = 93.5 Amperes Note: A size 3 AWG conductor @75 degrees C with an ampere rating of 100 amperes should be selected.
MFE-49. Determine the MINIMUM size 75 degree C rated conductors permitted to supply a 25-HP, 208 volt, three-phase, Design C, fire pump motor. A. 4 AWG B. 3 AWG C. 2 AWG D. 1 AWG
A. 430.6(A)(1) Tbl. 430.250 430.52(C)(1) Tbl. 430.52 FLC of motor = 30.8 Amperes x 250%=77Amperes
MFE-51. Determine the initial permitted operational setting of an adjustable inverse time circuit breaker used for branch-circuit, short-circuit, and ground fault protection of a 10 HP, 208-volt, three-phase, squirrel cage, Design B, continuous-duty motor. A. 30.8 Amperes B. 25.7 Amperes C. 77.0 Amperes D. 338.8 Amperes
B. 420.32(A)(1)
PE13-18. Continuous-duty motors with a marked service factor not less than 1.15 shall have the MINIMUM running overload protection sized at ________ of the nameplate rating of the motor. A. 115 percent B. 125 percent C. 130 percent D. 140 percent
B. 430.7(A)(2) 430.32(C) 54 Amperes x 130% = 70.2 Amperes
MFE-8. Determine the MAXIMUM ampere rating for an overload protective device responsive to motor current, as permitted by the NEC, used to protect a 20-HP, 230-volt, three-phase induction type AC motor with a temperature rise of 48 degrees C and a full-load ampere rating of 54 amperes indicated on the nameplate. A. 54.0 Amperes B. 70.2 Amperes C. 62.1 Amperes D. 75.6 Amperes
A. 430.6(A)(1) Tbl. 430.250 430.22 Tbl. 310.15(B)(16) FLC of motor = 88 amp x 125% = 100 amps Note: Size 2 AWG conductors rated at 75 C with an ampacity of 115 amperes should be selected
PE12-23. What MINIMUM size 75 C copper branch-circuit conductors are required to supply a continuous duty 208 volt, 3-phase, 30 horsepower motor with a nameplate current rating of 80 amperes? A. 2 AWG B. 3 AWG C. 4 AWG D. 6 AWG
A. 695.14.(E)
JFE-18. Which one of the following listed raceways is NOT permitted for use of enclosing control wiring for electric motor-driven fire pumps? A. Flexible metal conduit (FMC) B. Liquidtight flexible metal conduit (LFMC) C. Liquidtight flexible nonmetallic conduit (LFNC) D. Intermediate metal conduit (IMC)
B. 430.6(A)(1) Tb. 430.250 Tb. 430.52 240.6(A) FLC of motor - 65 amperes x 175% = 113.75 amperes Note: As the question was stated and exceptions are not permitted, you should select the next lower fuse value which is 110 amperes.
JFE-93. Disregarding exceptions, determine the MAXIMUM standard size time-delay fuses permitted for branch-circuit, short-circuit, and ground-fault protection for a 50 hp, 3-phase, 460-volt, induction-type motor with a FLA rating of 61 amperes marked on the nameplate. A. 100 amperes B. 110 amperes C. 115 amperes D. 125 amperes
B. Tbl 110.28
MFE-3. When a motor controller enclosure is installed outdoors and is subject to be exposed to sleet, it shall have a MINIMUM rating of ___________, where the controller mechanism is required to be operable when ice covered. A. Type 3 B. Type 3S C. Type 3R D. Type 3SX
A. 250.122(A) Tbl. 250.122(A)
MFE-36. What is the MINIMUM size equipment grounding conductor required for a 5HP, three-phase, 208 volt, continuous-duty motor having 20-ampere rating overload protection and short-circuit overcurrent protection rated at 30 amperes? A. 10 AWG B. 14 AWG C. 12 AWG D. 8 AWG
C. Tbl. 420.250 430.24(1) & (2) Tbl. 310.15(B)(16) 40 hp FLC = 52 amps x 100% = 52 amps 50 hp FLC = 65 amps x 100% = 65 amps 60 hp FLC = 77 amps x 125% = 96 amps Total 213 amps
PE14-22. Determine the MINIMUM size THWN copper feeder conductors required by the NEC to supply the following 480-volt, continuous duty, three-phase, induction-type, Design B, AC motors. *one 40 hp *one 50 hp *one 60 hp A. 2/0 AWG B. 3/0 AWG C. 4/0 AWG D. 250 kcmilq
D. 430.52(A)(1)
PE14-23. Two or more motors may be installed without individual overcurrent protection devices if rated less than 1 HP each; and the full load current rating of each motor does NOT exceed __________ amperes, if they are connected to a 120-volt, single-phase, 20-amperes rated branch-circuit. A. two B. four C. five D. six
C. Chpt 9, Tbl 9 Note: 3% of 480 volts = 14.4 voltage drop permitted CM = 1.732 x 21.2 x 100 amps x 390ft / 14.4 = 99,446 CM Size 1/0 AWG conductors with a circular mil area of 105,600 CM should be selected.
PE14-25. A three-phase, 480-volt, 100 amperes, noncontinuous load is located 390 feet from a panelboard. What MINIMUM size THWN aluminum conductors are required to supply the load, if the voltage drop is limited to 3 percent? (K=21.2) A. 2 AWG B. 1 AWG C. 1/0 AWG D. 2/0 AWG
C. 430.6(A)(1) Tbl. 430.250 Tbl. 430.52 FLC of motor = 30.8 amps x 250% = 77 amps
PE18-4. Determine the MAXIMUM permitted operational setting of an adjustable inverse-time circuit breaker used for branch-circuit, short circuit, and ground fault protection of a 10 hp, 208-volt, 3-phase, squirrel-case Design B, continuous-duty motor. Assume NO exceptions are applicable. A. 30.8 amps B. 35.7 amps C. 77 amps D. 80 amps
C. 455.6(A)(1) 56 amps (input rating) x 125% = 70 amps
PE18-9. A phase converter, with a 56 amp full-load single-phase input nameplate rating, that supplies variable loads shall have an input conductor ampacity of at LEAST ________. A. 56 amps B. 64.4 amps C. 70 amps D. 84 amps
C. Trade Knowledge (150,000 VA / 240 volts) = 625 amps
PE3-10. A 150kVA, single-phase transformer having a secondary voltage of 120/240 is to be installed at a multi-family dwelling. The current available at the secondary is _______ amperes. A. 329 B. 421 C. 625 D. 729
A. (15kVA x 1000) / 240 volts = 62.5 amps
PE7-25. A single-phase, 240-volt, 15kVA generator may have a maximum current load of NOT more than _______ amperes per line. A. 62.50 B. 31.25 C. 41.66 D. 52.50
A. 430.32(A)(1)
PE12-22. Where a motor has a temperature rise of 46 C indicated on the nameplate, for the purpose of selecting the overload device, this device shall be selected to trip at NO more than ________ of the motor full-load current rating. (Assume the value you select will enable the motor to start without tripping the overload device and modification of this value is not necessary). A. 115 percent B. 125 percent C. 130 percent D. 140 percent
C. 695.14(D)
PE15-15. Conductors between the controller and the diesel engine of a fire pump are required by the NEC to be ________? A 90 C rated B. 104 C rated C. stranded D. solid
D. 695.7(A) 480 volts x 80% = 12 amperes
PE13-5. In general, the MINIMUM voltage allowed at the line terminals of a 480-volt, three-phase, fire pump controller under motor starting conditions shall be ______. A. 466 volts B. 456 volts C. 432 volts D. 408 volts
D. 430.72(B)(2) Tbl 430.72(B)
MFE-97. What is MAXIMUM size overcurrent protection device permitted to protect size 14 AWG motor control circuit conductors, where the conductors are tapped from the load size of the motor branch-circuit, protective device and where the conductors are contained within the motor controller enclosure? A. 15 Amperes B. 20 Amperes C. 45 Amperes D. 100 Amperes
C. 430.109(C)(2) 15 amperes x 80% = 12 amperes
PE13-4. Where a 15-ampere rated general-use ac snap switch is to serve as a disconnecting means for a stationary ac electric motor, rated 2 hp or less and 300 volts or less, the NEC requires the MAXIMUM full-load current rating of the motor to be NO more than ________. A. 7.5 amperes B. 10 amperes C. 12 amperes D. 15 amperes
D. 440.22(A)
PE15-24. When sizing fuses or circuit breakers for a branch-circuit supplying a hermetic refrigerant motor-compressor, the device shall NOT exceed _______ of the rated load current marked on the nameplate of the equipment. A. 115 percent B. 125 percent C. 175 percent D. 225 percent
A. 502.115(B)
JFE-63. enclosures containing circuit breakers and motor controllers installed in a Class II, Division 2, hazardous location, shall be ____________, or otherwise identified for the location. A. dust-tight B. heavy-duty type C. rain-tight D. general-duty type
D. Tbl. 430.250 430.22 Tbl. 310.15(B)(16) Tbl. 31015(B)(2)(a) 25 hp motor flc = 74.8 amp x 125% = 93.5 amps 93.5 amps / .75 (temp correction) = 124.6 amps Note: the wire size needs to be increased because of the elevated temperature. Size 1 AWG THWN conductors with an ampacity of 130 amps should be selected.
PE14-11. What are the MINIMUM size THWN copper conductors required to serve a continuous-duty 25HP, 208-volt, three-phase motor? Given: the motor is on the end of the a 25 feet conduit run that contains only three (3) conductors at an expected ambient temperature of 50 C. A. 6 AWG B. 3 AWG C. 2 AWG D. 1 AWG
D. 695.4(B) & (C)(2)
PE15-3. When overcurrent protective devices are to be installed to protect fire pumps, they are to be sized to carry the ___________ of the fire pump motor(s). A. starting current B. full-load running current C. stopping current D. locked-rotor current
D 250.30(A)
PE16-6. In general, on the load side of the point of grounding of a separately derived system such as a transformer, a grounded conductor is NOT permitted to be connected to _________? A. an equipment ground conductor B. normally noncurrent-carrying metal parts of equipment. C. ground, the earth D. any of these
B. Tbl 430.250 63 amps x 1.1 (power factor) = 69.3 amps
PE16-9. Determine the full-load current of a 30 HP, three-phase, 230-volt, synchronous-motor with a 90 percent power factor. A. 63 Amps B. 69.3 Amps C. 76.23 Amps D. 86.62 Amps