Ricardos 4th test
T/F The maximum rating or setting of overcurrent protection for transformers under 1,000 volts per 450.3 is different for circuit breakers versus fuses.
False
T/F Per Article 240, the standard ampere ratings of fuses and circuit breakers must be used in an electrical distribution center.
False
T/F All fully rated systems are selectively coordinated.
False
T/F NEC 240.10 permits a supplementary fuse to be used where a branch circuit OCPD is required.
False
Determine the branch-circuit conductor size (copper, THW) needed for a 3-phase, 75-horsepower, 240-volt squirrel cage motor with a nameplate current of 188 amperes, a temperature rise of 40°C, and a marked service factor of 1.15 when starting current is not a problem. The terminals are rated 75°C.
250 kcmil conductors
T/F Since the 1971 NEC, 3-phase motors only need two phases protected with properly sized overload protection.
False
T/F The internal parts of fuses require maintenance.
False
Overcurrent protection for motor circuits are segmented into which of the following parts? a. Motor branch-circuit short-circuit and ground-fault protection b. Motor current conditioning for harmonics filtering c. Motor overload protection d. Motor speed overdrive protection e. Both a. and c.
e. Both a. and c.
Size the copper THW conductors needed to feed one 25-horsepower, 480-volt, 3-phase motor-compressor with a rated load current of 42 amperes and a branch-circuit selection current of 45 amperes when starting current is not a problem. The terminals are rated 75°C.
6 AWG THW copper conductors
Size the overcurrent protective device needed to feed one 25-horsepower, 480-volt, 3-phase motor-compressor with a rated load current of 42 amperes and a branch-circuit selection current of 45 amperes when starting current is not a problem.
70 ampere OCPD
The full-load current for a 7 1/2-hp induction-type squirrel cage motor which operates at 3-phase, 208 volts is ____ . a. 22.0 A b. 24.2 A c. 25.3 A d. 30.2 A NEC reference??
b. 24.2 A NEC: 430.23(C)
What section of Article 450 details the basic ampere rating sizing requirements for overcurrent protection of transformers? Select one: a. 450.1 b. 450.3 c. 450.4 d. Table 450.3(B)
b. 450.3
Article 450 covers the installation of transformers dedicated to supplying power to a fire pump installation as modified by Article ___ . a. 518 b. 695 c. 760 d. 770 NEC reference???
b. 695 NEC: 450.1
T/F A circuit breaker with an arc reduction maintenance switch (ARMS) provides an option where lower arc flash hazard levels can be achieved when it is necessary to do energized work.
True
T/F A fully loaded 3-phase motor protected by three properly-sized overload protective devices will be protected against single-phasing.
True
T/F A fully rated system is one in which all of the overcurrent protective devices have an individual interrupting rating at least as great as the available short-circuit current at their point of application.
True
T/F A motor branch-circuit disconnect listed to UL 98 or UL 489 can be used as a within sight of the motor disconnect.
True
T/F A transformer supplying a fire pump is not permitted to have secondary overcurrent protection.
True
T/F Each class of current-limiting fuse has its own unique physical dimensions so that fuses of a different class are not interchangeable. For instance, Class R fuses cannot be installed in Class J fuse equipment.
True
T/F Each motor used in a continuous-duty application and rated more than one horsepower is required to be protected against overload. A separate overload device that is responsive to motor current is one of four options permitted to protect against overload.
True
T/F For the purposes of the application of Table 450.3(A), a "supervised location" is a location where conditions of maintenance and supervision ensure that only qualified persons monitor and service the transformer installation.
True
T/F Table 450.3(A) provides provisions for both "any location" and "supervised locations only."
True
T/F The transformer primary overcurrent protective device supplying a fire pump must be rated to carry the sum of the locked-rotor current of the fire and pressure pump motors plus the full-load current of the accessory equipment.
True
T/F The two tables of concern for transformer protection are Table 450.3(A) for transformers over 1,000 volts, nominal and Table 450.3(B) for transformers 1,000 volts or less.
True
Determine the maximum standard size rating of the motor branch-circuit short-circuit and ground-fault protective device for a 5-horsepower, 208-volt, 3-phase, squirrel cage induction motor using dual element fuses when starting current of the motor is not an issue. a. 30 A b. 45 A c. 50 A d. 60 A NEC reference??
a. 30 A NEC: 240.6(A)
NEC ____ covers the requirements for the location of the motor controller disconnecting means. Select one: a. 430.102(A) b. 430.109 c. 430.111 d. 430.225
a. 430.102(A)
NEC ___covers interrupting rating requirements for equipment. a. 110.3 b. 110.9 c. 110.21 d. 110.27
b. 110.9
Determine the maximum rating of the motor branch-circuit short-circuit and ground-fault protective device, when starting current is a problem for a 3-horsepower, 230-volt, single-phase, capacitor motor using time-delay fuses. a. 30 A b. 35 A c. 40 A d. 50 A NEC reference??
b. 35 A NEC: 240.6(A)
A 3-phase, 750-kVA, 5.75% impedance transformer in an unsupervised location, with a primary voltage of 4,160 volts and secondary voltage of 480 volts, could have on the transformer primary a maximum fuse size amp rating of ___ for the primary OCPD. Select one: a. 200 A b. 350 A c. 400 A d. 600 A
b. 350 A
The type of motor disconnecting means is covered by NEC ? . Select one: a. 430.102(A) b. 430.109 c. 430.111 d. 430.225
b. 430.109
Part ? of Article 430 covers the requirements for motor controllers. Select one: a. IV b. VII c. IX d. XI
b. VII
What NEC section limits the use of slash voltage rated circuit breakers for solidly grounded wye systems only where the line-to-ground voltage does not exceed the lower of the two values and the line-to-line voltage does not exceed the higher value? a. 240.4 b. 240.67 c. 240.85 d. There is no such NEC requirement.
c. 240.85
T/F The voltage rating of the OCPD must be equal to but never greater than the circuit voltage.
False
T/F When increased sizing of the overcurrent protective device is utilized on the secondary side of a transformer, overcurrent protection on the primary side, sized closer to the load, is typically required.
False
Because of the ____ impedance path, a 3-phase bolted fault condition is typically assumed to be the highest level of fault current. a. high b. low c. reactive d. resistive
b. low
Identify the NEC section where the following provision is located: A circuit breaker is used on a circuit having an available fault current higher than its marked interrupting rating by being connected on the load side of an acceptable overcurrent protective device having a higher rating. In this section the circuit breaker shall meet the requirements specified in (A) or (B), and (C). a. 240.40 b. 240.41 c. 240.86 d. 240.87
c. 240.86
For a 7% impedance transformer over 1,000 volts, without coordinated thermal overload protection, in a supervised location, a primary fuse could be sized up to __ , or the next commercially available ampere rating without secondary protection. Select one: a. 115% b. 125% c. 250% d. 500%
c. 250%
A horsepower-rated switch or circuit breaker is permitted as both the motor controller and disconnecting means in accordance with NEC ? . Select one: a. 430.102(A) b. 430.109 c. 430.111 d. 430.225
c. 430.111
Overload protection for continuous-duty motors one horsepower or less, automatically started, is covered by NEC ? . Select one: a. 430.6(A)(1) b. 430.22(C) c. 430.32(B) d. 430.52(C)(1)
c. 430.32(B)
MCPs are recognized devices (not listed) and are permitted by _____ to provide motor branch-circuit short-circuit and ground-fault protection, if used as part of a listed combination with a starter. a. 430.32 b. 430.52(C)(1) c. 430.52(C)(3) d. 430.53
c. 430.52(C)(3)
The minimum ampacity for branch-circuit conductors, which supply a 75-horsepower, 3-phase, induction-type squirrel cage motor which operates at 460 volts, is ____ . a. 77 A b. 96 A c. 120 A d. 192 A
c. 120 A
The minimum ampacity rating and size of the copper, THW branch-circuit conductors for a 3-phase, 125-horsepower, 460-volt squirrel cage induction motor is ___ and a ____conductor. The terminals are rated 75°C a. 125 A / 1/0 AWG b. 156 A / 2/0 AWG c. 195 A / 3/0 AWG d. 210 A / 4/0 AWG NEC reference??
c. 195 A / 3/0 AWG NEC: 310.15(B)
A separate motor overload device for a continuous-duty motor more than one horsepower with a 1.15 service factor must be selected to trip or be rated at no more than ___ of the motor nameplate full-load current rating. Assume the motor starts and runs continuously without nuisance tripping for this selection. a. 50% b. 72% c. 115% d. 125%
d. 125%
T/F For a motor branch circuit where the motor is within 50 feet and within sight of the branch-circuit disconnect, branch-circuit fuses (if properly sized) in conjunction with a UL 98 disconnect can be suitable for these four functions: motor branch-circuit disconnect, motor branch-circuit short-circuit and ground-fault protection, motor controller, and within sight motor disconnect.
True
When determining the overcurrent protection requirements for transformers in a circuit, other requirements from Article(s) ? may also need to be investigated .I. 230 II. 240 III. 408 IV. 517 a. I., II., and III. only b. I., II., III., and IV. c. I. and III. only d. II. and III. only
a. I., II., and III. only
Motor branch-circuit short-circuit and ground-fault protection and motor overload protection shall be permitted to be combined in a single protective device where the rating or setting of the device provides the overload protection specified in 430.32. a. True b. False NEC reference??
a. True NEC: 430.55
For a transformer 1,000 volts or less, with secondary current of 5 amperes, the secondary overcurrent protective device could be sized up to ? of the transformer-rated current where both primary and secondary protection is provided. a. 125% b. 167% c. 250% d. 300% NEC reference??
b. 167% NEC: Table 450.3(B)
For a part-winding connected motor, the ampacity of the branch-circuit conductors on the line side of the controller shall not be less than 125% of the motor full-load current as determined by 430.6(A)(1). The ampacity of the conductors between the controller and the motor shall not be less than___ of the motor full-load current rating as determined by 430.6(A)(1). a. 50% b. 62.5% c. 72% d. 125% NEC reference??
b. 62.5% NEC: 430.22(D)
A 600-volt or less transformer equipped with coordinated thermal overload protection by the manufacturer and arranged to interrupt the primary current shall be permitted to have primary overcurrent protection rated or set at a current value that is not more than ____ times the rated current of the transformer for transformers having not more than 6% impedance and not more than ____ times the rated current of the transformer for transformers having more than 6% but not more than 10% impedance. Select one: a. 4 / 6 b. 4 / 10 c. 6 / 4 d. 6 / 10
c. 6 / 4
The requirements for motor-circuit overcurrent protection for motors over 1,000 volts are covered in what section of Article 430? Select one: a. 430.102(A) b. 430.109 c. 430.111 d. 430.225
d. 430.225
T/F Primary inrush current characteristics can vary by transformer design.
True
Which fuse type is not a branch circuit OCPD? a. UL Class J b. UL Class L c. UL Class R d. UL recognized high speed fuse
d. UL recognized high speed fuse
T/F Listed or labeled equipment must be installed and used in accordance with any instructions included in the listing or labeling.
True
T/F Molded case circuit breakers (MCCBs) are the most prevalent circuit breakers in use for 15 amperes to 2,500 amperes.
True
T/F Motor controllers serve as the motor ON/OFF function.
True
T/F Overcurrent protective devices on transformer primary may require increased sizing due to the magnetizing inrush current.
True
T/F Section 110.3 provides criteria and considerations for the evaluation of equipment and recognizes listing or labeling as a means of establishing suitability.
True
T/F When fault current is within the current-limiting range of a current-limiting OCPD, the thermal energy and magnetic (mechanical) forces can be greatly reduced. The levels of both thermal energy and magnetic forces are proportional to the square of the fault current that flows
True
T/F When the conductor ampacity does not correspond to a standard OCPD ampere rating, the next standard OCPD ampere rating is permitted if that rating does not exceed 800 amperes, and if the conductors are not supplying a circuit with more than one receptacle for cord-and-plug portable loads
True
Where the value for a branch-circuit short-circuit and ground-fault protective device determined by Table 430.52 for a dual-element fuse or inverse time circuit breaker does not correspond to a standard ampere rating, a __ ampere rating or setting that does not exceed the next higher standard ampere rating shall be permitted. a. higher b. lower NEC reference??
a. higher NEC:430.52(C)(1) Exception No. 1
Fuses and circuit breakers are intended to protect conductors and equipment from the effects of potentially harmful _____. a. overcurrents b. overvoltages c. both a. and b.
a. overcurrents
A 3-phase, 750-kVA, 5.75% impedance transformer in an unsupervised location, with a primary voltage of 4,160 volts and secondary voltage of 480 volts, would have a secondary circuit breaker sized at a maximum of ___ . Select one: a. 800 A b. 1200 A c. 1500 A d. 1800 A
b. 1200 A
Short-circuit current _____ the normal conducting path. a. flows in the reverse direction as overload current in b. flows outside c. is entirely confined to
b. flows outside
Determine the maximum rating of time-delay fuses needed for a 3-phase, 75-horsepower, 240-volt squirrel cage motor with a nameplate current of 188 amperes, a temperature rise of 40°C, and a marked service factor of 1.15 when starting current is not a problem. Assume the motor will start with this selection.
350 ampere time delay fuse
T/F A 600-volt AC fuse or circuit breaker is considered to have a 600-volt DC rating, even if it is not marked with a DC voltage rating.
False
T/F A disconnecting means "in sight from the motor" is used for insulating the motor circuit for maintenance and serves as an emergency disconnecting means.
False
T/F A mini-circuit breaker (UL 1077 supplemental protector) or supplemental fuses are suitable for use as motor branch-circuit short-circuit and ground-fault protection.
False
T/F Overload current is confined to the normal conductive path provided by the conductors, circuit devices, and loads of the distribution system.
True
T/F The motor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the starting current of the motor. NEC reference??
True NEC: 430.52
Which of the following characteristics of motor branch circuits make them unique branch circuits? I. Circuit components such as starters, overload heaters, and contactors which have low short-circuit current withstands or SCCRs II. Combination of higher probability to incur faults III. The desire for various levels of functionality, such as remote push button control and automatic control IV. The harsh demand of motor loads, such as inrush and locked rotor currents V. The multitude of potential devices used in motor circuits a. I. and II. only b. I., II., III., IV., and V. c. I., III., and V. only d. II., III., and IV. only
b. I., II., III., IV., and V.
A ___ protective device is one that clears a fault current in one-half cycle or less and reduces the amount of short-circuit current let-through. a. branch circuit b. current-limiting c. motor circuit d. surge
b. current-limiting
For a wye-start, delta-run connected motor, the ampacity of the branch-circuit conductors on the line side of the controller shall not be less than 125% of the motor full-load current as determined by 430.6(A)(1). The ampacity of the conductors between the controller and the motor shall not be less than ____ of the motor full-load current rating as determined by 430.6(A)(1). a. 50% b. 62.5% c. 72% d. 125% NEC reference??
c. 72% NEC reference: 430.22(C)
Which of the following statements is not correct per Article 100 definition? a. Branch-circuit overcurrent protective devices are capable of being able to provide a full range of overcurrent protection from rated current to its interrupting rating. b. Branch-circuit overcurrent protective devices are intended for protection of a service, feeder or branch circuit of an electrical system. c. Branch-circuit overcurrent protective devices must be listed in combination with the specific device it is intended to protect. d. Branch-circuit overcurrent protective devices must have interrupting rating sufficient for the application, but not less than 5 kA.
c. Branch-circuit overcurrent protective devices must be listed in combination with the specific device it is intended to protect.
T/F Supplementary overcurrent protective devices are permitted to be used as a substitute for a branch-circuit OCPD or where a branch-circuit OCPD is required (240.10).
False
T/F Secondary protection is not required for a transformer 1,000 volts or less, with primary overcurrent protection sized at 125% feeding a 3-phase, 4-wire panelboard NEC reference???
False NEC: Table 450.3(B)
Molded case circuit breakers, insulated case circuit breakers, and low voltage power circuit breakers are ____ . a. application-limited OCPDs which are suitable for specific branch circuit applications, under limited conditions per the NEC b. branch circuit overcurrent protective devices c. supplementary OCPDs
b. branch circuit overcurrent protective devices
Each motor used in a continuous-duty application and rated more than one horsepower is required to be protected against overload. Which of the following are permitted to protect such motors from overload? Select one: a. A thermal protector integral with the motor, approved for use with the motor it protects on the basis that it will prevent dangerous overheating of the motor due to overload and failure to start b. A protective device integral with a motor that will protect the motor against damage due to failure to start if the motor is part of an approved assembly that does not normally subject the motor to overloads c. Either a. or b. d. Neither a. nor b.
c. Either a. or b.
T/F A motor is located 100 feet from the motor control center that provides the motor branch-circuit disconnect. An instantaneous-trip circuit breaker can be used for this application as long as it is within sight of the motor and the motor disconnect.
False
T/F For transformers 1,000 volts or less, the secondary overcurrent protection device can be split up to six devices, provided the sum of the ratings does not exceed that of the single device and the conditions of Article 240 and Article 408 are satisfied.
True
Separate motor overload protection shall be based upon the motor nameplate ___ rating. a. current b. efficiency c. power d. voltage NEC reference??
a. current NEC reference: 430.6(A)(2)
A transformer utilizing primary and secondary protection with a primary current of 100 amperes at 480 volts, and secondary current of 200 amperes at 240 volts, would have the overcurrent primary overcurrent protection sized at a maximum of ____ and secondary protection sized at a maximum of _____ . a. 125 A / 125 A b. 125 A / 250 A c. 250 A / 125 A d. 250 A / 250 A NEC reference??
d. 250 A / 250 A NEC: Table 450.3(B)
The maximum size for an overcurrent protective device for a motor control circuit transformer with a primary current of less than two amperes is not more than __ . a. 115% b. 125% c. 250% d. 500% NEC reference??
d. 500% NEC: 430.72(C)(4)
The minimum size copper THW conductor for branch-circuit conductors that supply a 10-horsepower, 230-volt, single-phase, alternating-current motor is ___ . The terminals are rated at 75°C. a. 1/0 AWG b. 2 AWG c. 4 AWG d. 6 AWG NEC reference??
d. 6 AWG NEC: 430.22
A 3-phase, 750-kVA, 5.75% impedance transformer in an unsupervised location, with a primary voltage of 4,160 volts and secondary voltage of 480 volts, could have a primary circuit breaker sized at a maximum of ___ . Select one: a. 130 A b. 400 A c. 500 A d. 700 A
d. 700 A
Which of the following is a motor circuit function discussed in this lesson? a. At the motor or in sight from the motor disconnect b. Motor branch-circuit and controller disconnect c. Motor controller d. All of the above
d. All of the above
Determine the maximum overload protection trip or rating for a 3-phase, 75-horsepower, 240-volt squirrel cage motor with a nameplate current of 188 amperes, a temperature rise of 40°C, and a marked service factor of 1.15 when starting current is not a problem.
235 ampere overload trip or rating
T/F A motor switch listed to UL 508 can be used as the motor branch-circuit disconnect
False
T/F Branch circuit fuses do not have to be marked with their ampere rating.
False
T/F Devices are permitted to only perform one motor circuit function.
False
T/F For motor branch circuit applications, the motor branch circuit short-circuit and ground fault protective device can be located anywhere on the motor branch circuit since short-circuit currents stay within the normal conducting path.
False
Which NEC article applies to electric motor-driven air-conditioning and refrigerating equipment and to the branch circuits and controllers for such equipment? Select one: a. 430 b. 440 c. 445 d. 450
b. 440
Branch-circuit conductors supplying a single motor compressor shall have an ampacity not less than 125% of either the motor-compressor rated load current or the branch-circuit selection current, whichever is greater. For a wye-start, delta-run connected motor-compressor, the selection of branch-circuit conductors between the controller and the motor-compressor shall be permitted to be based upon ___ of either the motor-compressor rated-load current or the branch-circuit selection current, whichever is greater. a. 72% b. 115% c. 125% d. 225% NEC reference??
a. 72% NEC: 440.32
The scope of Article 450 indicates that this article covers the installation of all transformers. There are __ exceptions that modify this Article 450 scope statement. Select one: a. 3 b. 7 c. 8 d. 9
c. 8
Part ? of Article 430 covers the requirements for the motor disconnecting means. Select one: a. IV b. VII c. IX d. XI
c. IX
How can a 600-volt or less branch-circuit OCPD be identified as being current limiting? a. Ask the manufacturer. b. Read the data sheet. c. The circuit breaker or fuse will be marked "current-limiting". d. There are no 600-volt current-limiting branch circuit OCPDs
c. The circuit breaker or fuse will be marked "current-limiting".
Conductors that supply a single motor used in a continuous-duty application shall have an ampacity of not less than _____ of the motor full-load current rating, as determined by 430.6(A)(1), or not less than specified in 430.22(A) through (G). a. 50% b. 62.5% c. 72% d. 125% NEC reference???
d. 125% NEC reference: 430.22
The motor-compressor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the starting current of the motor. A protective device having a rating or setting not exceeding 175% of the motor-compressor rated load current or branch-circuit selection current, whichever is greater, shall be permitted, provided that, where the protection specified is not sufficient for the starting current of the motor, the rating or setting shall be permitted to be increased, but shall not exceed ___ of the motor rated-load current or branch-circuit selection current, whichever is greater. a. 72% b. 115% c. 125% d. 225% NEC reference??
d. 225% Nec: 440.22(A)
Which statement about supplementary protectors is not correct? a. Cannot be used in place of branch-circuit protection b. Intended where branch-circuit protection not required c. Recognized to UL 1077 d. Suitable for branch-circuit protection
d. Suitable for branch-circuit protection
The values given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 are generally used to determine which of the following for motor branch circuit? a. Ampacity of conductors b. Branch-circuit short-circuit and ground-fault protection c. Motor overload protection d. a. and b. e. a. and c NEC reference??
d. a. and b. NEC reference: 430.6(A)(1)
Magnetic motor starters listed to UL 508 are suitable for use _____ . a. as motor branch-circuit and controller disconnect b. as motor controller c. as motor overload protection d. at the motor or in sight from the motor disconnect e. both b. and c.
e. both b. and c.
