Ricardos 3rd year second test (code??) ch.1-9
Match the correct Ampere Rating Range for each type of fuse. -Class T fuse A. 601-6,000A B. 1-1,200A C. 1/2 - 60A D. 1/10-600A
B. 1-1,200A
T/F An inverse time-current characteristic is defined as the higher the overcurrent level, the faster the reaction time or interrupting time of the overcurrent device.
True
T/F 230.95 requires GFPE on a 1,000-ampere service disconnect for a 208/120 volt, solidly grounded system.
False
T/F Improperly grounding of neutral conductors has no effect on a GFPE to detect ground fault currents accurately.
False
T/F Fuse time-current curves and circuit breaker time-current curves are always the same shape.
False
A(n) ____ is a current greater than the equipment rated current or conductor ampacity, which is confined to the normal conductive paths provided by the conductors and other equipment. a. branch-circuit overcurrent device b. overcurrent c. overload d. supplementary overcurrent device
C. overload
T/F A fuse or circuit breaker with a 600-volt AC rating is permitted to be used on 300-volt DC application by the half voltage rule in NEC Article 240.
False
T/F Ground-fault relays will protect against high-magnitude ground faults
False
T/F NEC 240.21, with some exceptions, requires overcurrent protection in each ungrounded conductor to be located where the conductors connect to the load
False
Interrupting ratings on AC rated circuit breakers are used for ___? a. AC systems only b. DC systems only c. both AC and DC systems d. none of the above
a. AC systems only
Low voltage fuses (600 volts or less) permitted to be used to protect service, feeder, and branch circuits are called branch-circuit overcurrent protective devices or branch-circuit fuses and are covered by the ____Standard a. UL 248 b. UL 489 c. UL 1099 d. UL 2579
a. UL 248
T/F A Type ICCB uses electronic sensor technology.
True
T/F A fuse listed to UL 2579 with a photovoltaic DC voltage rating is suitable for PV source and output circuit applications at its DC voltage rating or less, but may not be suitable for general industry DC applications.
True
T/F A service conductor is never a tap conductor.
True
T/F A specific MCP (motor circuit protector) can only be utilized with a motor starter that is listed for use with that MCP.
True
T/F A typical ground-fault relay has an adjustable ground fault current pick-up setting and time-delay pick-up setting.
True
T/F For healthcare facilities, 517.17(B) requires the feeders to have GFPE if the service has GFPE.
True
T/F For most circuits, the phase OCPDs provide protection for all types of short circuits, including ground faults.
True
T/F Fuses and circuit breakers which are intended to interrupt current at fault levels must have an interrupting rating at applied voltage sufficient for the available short circuit at its line terminals
True
T/F Inappropriate GFPE settings are a common cause of main service nuisance power outages.
True
T/F Large ampacity service-entrance overcurrent protective devices may not always sense and open lower level ground-fault conditions prior to extensive damage.
True
T/F The effective time-current curve for ground-fault protection consists of the curve for the ground-fault relay and the phase overcurrent protective device
True
T/F The most commonly required point where GFPE is required is service disconnects of 1,000 amperes or more for 480/277-volt, 3-phase, 4-wire, solidly grounded wye electrical systems.
True
T/F The two types of ground-fault sensing relays are zero sequence and residual.
True
T/F To comply with 110.9 of the NEC, the overcurrent protective device selected must have an interrupting rating equal to or greater than the available fault current.
True
T/F When an AC motor is started across the line, a high inrush current occurs.
True
T/F GFPE is required for a 1,000-ampere service disconnect with 800-ampere fuses for a 480/277-volt, 3-phase, 4-wire, solidly grounded wye electrical system. NEC reference??
True NEC reference: 230.95
Which of the following is typically true regarding motor overcurrent protection? I. Motor branch-circuit short-circuit and ground-fault protection is located at the beginning of a motor branch circuit in order to provide short-circuit and ground-fault protection to the entire circuit. II. Overload relays and other motor overload protective devices are selected on the motor nameplate current ratings and are intended to protect the motor windings and the branch circuit wire and components against overloads. Since overloads stay within the normal circuit conductive path, the overload protective device can be located anywhere in the motor branch circuit. a. I. b. II. c. Both I. and II. d. Neither I. nor II
c. Both I. and II.
Conductors supplying several motors, or a motor(s) and other load(s), shall have an ampacity not less than the sum of ? of the full-load current rating of the highest rated motor, determined by 430.6(A), plus the sum of the full-load current ratings of all other motors determined by 430.6(A), plus 100% of the non-continuous non-motor load, plus 125% of the continuous non-motor load a. 100% b. 125% c. 300% d. 800% NEC Reference?
b. 125% NEC reference: 430.24
Feeder taps not over 10 feet long are covered by NEC section ____? a. 240.21(A) b. 240.21(B)(1) c. 240.21(C)(3) d. 240.21(C)(6)
b. 240.21(B)(1)
A device capable of providing protection for service, feeder, and branch circuits and equipment over the full range of overcurrents between its rated current and its interrupting rating is a(n) ____? . a. ampacity protector b. branch-circuit overcurrent protective device c. feeder protector d. service conductor overcurrent protective device
b. branch-circuit overcurrent protective device NEC reference: 100
The electrical resistance of the fuse link is so low, it simply acts as a(n) ____ during the normal circuit operation. a. capacitor b. conductor c. inductor d. resistor
b. conductor
The highest current at rated voltage that a device is identified to interrupt under standard test conditions describes ___? a. ampacity rating b. interrupting rating c. quality current rating d. short-circuit rating NEC reference??
b. interrupting rating NEC reference: 100
What type of circuit breaker is the most prevalently used for 15-ampere to 2,500-ampere systems? a. ICCB b. LVPCB c. MCCB d. MCP
c. MCCB
Which NEC section provides the separate overload device rating or trip setting requirement for continuous-duty motors more than one horsepower? a. 430.6 b. 430.7 c. 430.32(A)(1) d. 430.52(C)
c. 430.32(A)(1)
Tap conductors shall be permitted to be protected against overcurrent in accordance with ____? a. 210.19(A)(4) b. 240.21 c. 368.17(B) d. 430.53(D) e. All of the above NEC Reference???
e. All of the above NEC reference: 210.19(A)(4)
Match the correct Ampere Rating Range for each type of fuse. -Class K fuse A. 601-6,000A B. 1/8-600A C. 1/2 - 60A D. 1-600A
B. 1/8-600A
Match the correct Interrupting Range for each type of fuse. -Class G fuse A. 200kA B. 100KA C. 200kA or 300kA D. 10kA
B. 100KA
Match the correct Memory Word for each type of fuse...... Class G fuse A. Cube B. Growing C.Large D. Junior
B. growing
An overcurrent that stays in the normal conduction path could be a(n) _____ A. ground fault B. overload C. short current D. B and C E. A, B, and C
B.overload
Match the correct Ampere Rating Range for each type of fuse. -Class G fuse A. Fractional - 30A B. 1-100A C. 1/2 - 60A D. 1/8 - 600A
C. 1/2 - 60A
As generally required in the NEC, match the overcurrent device ampere rating for the following small conductor sizes. 16 AWG copper A. 25 amperes B. 30 amperes C. 10 amperes D. 20 amperes
C. 10 amperes
T/F Section 240.21 provides specific 10-foot and 25-foot tap rules for service conductors.
False
T/F Instantaneous trip circuit breakers are also referred to as motor circuit protectors (MCPs) and are intended only for motor branch circuit short-circuit and ground-fault protection.
True
T/F Once a feeder conductor has been tapped with smaller tap conductors serving downstream equipment, it is not permissible to apply a second tap on the first tap. (In essence, do not tap a tap.) NEC reference??
True NEC reference: 240.21
T/F Cartridge fuses in circuits of any voltage where accessible to other than qualified persons and all fuses in circuits over 150 volts to ground shall be provided with a disconnecting means on their supply side. There are exceptions. NEC reference?
True NEC reference: 240.40
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 6 (AC-1) is ? . (Note: AC-1 and AC-2 are 3-phase, L-L-L loads. They do not require a neutral conductor to operate.) Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result a. 11,589 A b. 13,249 A c. 16,729 A d. 31,645 A
a. 11,589 A
What is the "C" value for one 4/0 AWG/phase (600-volt, copper, three conductors) in a steel conduit? a. 15,082 b. 16,392 c. 16,673 d. 17,483
a. 15,082
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 3 (LPA) is ? . Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result a. 15,570 A b. 19,750 A c. 24,233 A d. 50,641 A
a. 15,570 A
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 1 (transformer secondary terminals) is ? . Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result. a. 46,264 A b. 49,760 A c. 52,000 A d. 65,000 A
a. 46,264 A
Overcurrent protection for transformers requires special considerations due to the magnetizing inrush current, which occurs on the ? when the transformer is energized. a. primary b. secondary c. primary and secondary
a. primary
Match the correct Memory Word for each type of fuse...... Class L fuse A. Junior B. Large C. cube D. growing
B. large
Match the correct Interrupting Range for each type of fuse. -Class T fuse A. 200kA or 300kA(RK1) B. 100KA C. 200kA D. 10kA
C. 200kA
Match the correct Interrupting Range for each type of fuse. -class J fuse A. 200kA B. 100KA C. 200kA or 300kA D. 10kA
C. 200kA or 300kA
Match the correct Memory Word for each type of fuse...... Class CC Fuse A.tiny B.Cube C.charlie Chaplin D. rejection
C. Charlie Chaplin
A type of short circuit defined as an unintentional connection between an ungrounded conductor and ground, an equipment grounding conductor, or grounded equipment is a(n) _____ a. current limiter b. ground conductor c. ground fault d. overload
C. ground fault
Match the correct Interrupting Range for each type of fuse. -Class H fuse A. 200kA B. 100KA C. 200kA or 300kA D. 10kA
D. 10kA
Match the correct Memory Word for each type of fuse...... Class CF fuse A. Charlie Chaplin B. Rejection C. Tiny D. Cube
D. Cube
T/F Application limited OCPDs that are permitted by the NEC in place of branch-circuit OCPDs can be used at any point in the distribution system with restrictions.
False
T/F Dual-element time-delay fuses consist of two distinctive and separate types of elements that are connected in parallel inside the fuse. One is an overload element and the other is a short-circuit element
False
T/F Nontime-delay Class J fuses have slow response times and are best applied for equipment with high inrush currents or temporary overloads or surge currents.
False
T/F Most circuit breakers and fuses would "nuisance open" on motor startup if sized to provide motor and branch-circuit overload protection. As a result, motor branch circuits are permitted by NEC requirements to have two separate overcurrent protective devices located at physically different locations
True
T/F A circuit breaker is a device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating. NEC reference?
True NEC reference: 100
Which is/are sources of circuit breaker maintenance information? I. Circuit breaker manufacturers' manuals II. NETA Maintenance Testing Specification for Electrical for Electrical Power distribution Equipment and Systems .III. NFPA 70B Recommended Practice for Electrical Equipment Maintenance a. I. only b. I., II., and III. c. II. only d. II. and III. e. III. Only
b. I., II., and III.
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 10 (combination motor controller) is ? . Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result. a. 7,649 A b. 12,850 A c. 16,449 A d. 21,759 A
c. 16,449 A
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 5 (LPB) is ? . Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result. a. 5,600 A b. 10,000 A c. 16,595 A d. 25,100 A
c. 16,595 A
Which is not a category for overcurrent devices? a. Application limited OCPDs suitable for specific branch-circuit applications, under limited conditions b. Branch-circuit OCPDs c. Nonautomatic OCPDs d. Supplementary OCPDs
c. Nonautomatic OCPDs
The short-circuit current at the end of a 480-volt, 3-phase, 50-foot, 800-ampere, copper feeder bus with a short-circuit current of 60,000 amperes at the beginning of the run is ? . Select the answer closest to your calculated result a. 10,489 A b. 20,674 A c. 39,568 A d. 49,200 A
d. 49,200 A
Which of the following are reasons why short-circuit studies involve calculating a bolted 3-phase fault condition? a. Three phases bolted together create a near zero impedance connection. b. A "worst case" (highest current) condition that results in maximum 3-phase thermal and mechanical stress in the system is established. c. A "worst case" condition is typically what is needed to ensure proper equipment ratings such as OCPD interrupting rating and short-circuit current ratings (SCCR). d. All of the above
d. All of the above
A conductor, other than a service conductor, that has overcurrent protection ahead of its point of supply that exceeds the value permitted for similar conductors that is protected as described elsewhere in 240.4 best describes ____? a. branch-circuit conductor b. feeder conductor c. service conductor d. tap conductor NEC reference??
d. tap conductor NEC reference: 240.2
What is the interrupting rating for LVPCBs? a. From 0 kA to 100,000 kA b. From 25 kA to 300,000 kA c. From 42 kA to 200 kA d. From 100 kA to 300 kA
c. From 42 kA to 200 kA
_____ is a system intended to provide protection of equipment from damaging line-to-ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit a. Ground alarm b. Ground-fault interrupter circuit c. Ground-fault protection of equipment d. Ground motor detection NEC reference?
c. Ground-fault protection of equipment NEC reference: 100
Which of the following is not a required item for tap conductors over 25 feet long used in a high bay manufacturing building over 35 feet high at the walls? a. Conditions of maintenance and supervision ensure that only qualified persons service the systems. b. The ampacity of the tap conductors is not less than one-third the rating of the overcurrent device protecting the feeder conductors. c. The tap conductors are not over 7.5 meters (25 feet) long horizontally and not over 30 meters (100 feet) total length. d. The tap conductors are sized 8 AWG copper or 2 AWG aluminum or larger.
c. The tap conductors are not over 7.5 meters (25 feet) long horizontally and not over 30 meters (100 feet) total length.
Typically what is the single most influencing factor on the magnitude of the available short-circuit current at the service? a. Conductors from the service transformer to the service equipment b. Motors on the system c. Transformer supplying the service d. Utility system up to line-side of the service transformer
c. Transformer supplying the service
Current-limiting circuit breakers can be___? a. inherently current-limiting in their design b. internally fused c. both a. and b. d. neither a. nor b.
c. both a. and b.
Part of the process of a circuit breaker interrupting an overcurrent is that the trip unit senses the overcurrent, and releases or unlatches the contacts. This then permits the movable ____to start to travel or part from the stationary contact a. arc chutes b. bi-metal element c. contact d. magnetic element
c. contact
A fuse uses a conductive ____ link or links encapsulated in a tube with compacted silica sand and connected to contact terminals. a. break out b. filament c. fusible d. malleable
c. fusible
Separate motor and branch-circuit overload protection is sized based upon the ? . a. Full load current based on motor horsepower in NEC Tables 430.247 to 430.250 b. maximum locked-rotor current c. motor nameplate full-load current d. start-up current NEC reference???
c. motor nameplate full-load current NEC reference: 430.32
The ____ of ground-fault protection can depend upon the components, wiring, setting, and maintenance of not just the relay, but also the proper installation of the building wiring system. a. ampacity b. control c. reliability d. setting
c. reliability
Nontime-delay fuses use a(n) ____element fuse construction. a. dissimilar metal b. dual c. single d. suppression
c. single
The operating characteristics of an OCPD trip curve can be visually displayed in a ___ curve. a. capacitance b. current-voltage c. time-current d. time-delay
c. time-current
The ground-fault protection system must operate to cause the service disconnect to open all ungrounded conductors of the faulted circuit. The maximum setting of the ground-fault protection permitted is ? , and the maximum time-delay setting is ? for ground-fault currents equal to or greater than 3,000 amperes a. 500 A / 1 second b. 1,000 A / 1 second c. 1,000 A / 3 seconds d. 1,200 A / 1 second
d. 1,200 A / 1 second
In some cases, momentary high inrush currents during motor starting can reach as high as ? times the normal running current amperes during the first 1/2 cycle. a. 2 b. 4 c. 10 d. 20
d. 20
Using 430.52 and Table 430.248, what is the maximum size dual-element fuse short-circuit and ground-fault protective device allowed for a 10-horsepower, 230-volt, single-phase motor, assuming the motor starts with this size? a. 50 A b. 70 A c. 80 A d. 90 A
d. 90 A
Photovoltaic applications present unique protection requirements resulting in the development of fuses with specific features for PV source circuits and output circuits application. Fuses listed to ____ standard are required for these PV applications a. UL 248 b. UL 489 c. UL 1099 d. UL 2579
d. UL 2579
A circuit breaker's current sensing trip unit can be ___? a. electronic b. magnetic only c. thermal magnetic d. any of the above
d. any of the above
Zero sequence ground-fault protection monitors current in the _____ . a. grounding strap b. neutral conductor c. phase conductors d. b. and c.
d. b. and c.
Most circuit-breaker terminal connectors are rated ___? .a. 60°C b. 75°C c. 90°C d. both a. and b
d. both a. and b
t/f When doing an arc-flash incident energy hazard analysis, the available bolted fault current is necessary for determining the hazard. It is recommended that the calculation be as accurate as possible.
true
T/F Generally, conductors shall be protected at their ampacities by branch-circuit overcurrent devices. NEC reference??
true NEC reference: 240.4
How can it be determined if a circuit breaker is current-limiting? a. All 200 A or less circuit breakers are current-limiting b. It will be marked "Current-Limiting" c. It will have an interrupting rating greater than 10kA d. None of the above
b. It will be marked "Current-Limiting"
Which type of circuit breaker is designed to be reconditioned? a. Insulated case circuit breakers b. Low-voltage power circuit breakers c. Molded case circuit breakers
b. Low-voltage power circuit breakers
What devices are permitted to be used as branch circuit OCPDs in service, feeders, and branch circuits? a. Instantaneous (only) circuit breakers (MCPs) b. Molded Case Circuit Breakers (MCCBs) c. Supplementary protectors d. All of the above
b. Molded Case Circuit Breakers (MCCBs)
Ground-fault protection of equipment is not permitted for ? or required for a continuous industrial process where a non-orderly shutdown would introduce additional or increased hazards. a. electronically-actuated fuses b. fire pump circuits c. industrial buildings d. phase converters NEC reference??
b. fire pump circuits NEC reference: 695.6(G)
Electronic trip units can offer ___accuracy, additional trip adjustments, programming, and communication. a. decreased b. increased c. modest levels of d. unchanged levels of
b. increased
An existing 50-ampere branch circuit is located in a kitchen for the connection of cooking equipment. A tap conductor is used to supply a new wall-mounted oven and a new counter-mounted cooking unit. The wiring method used between the 50-ampere junction box and the new cooking equipment is Type NM cable. What is the minimum size conductor and maximum conductor length allowed by Code for this installation a. 12 AWG, 50' b. 10 AWG, 50' c. 12 AWG, unlimited length, but not longer than necessary d. 10 AWG, unlimited length, but not longer than necessary
c. 12 AWG, unlimited length, but not longer than necessary
The NEC permits a set of conductors feeding a single load, or each set of conductors feeding separate loads, to be connected to a transformer secondary without overcurrent protection at the secondary, as specified in __? a. 230.91 b. 240.2 tap conductors definition c. 240.21(C)(1) through (C)(6) d. 450.3
c. 240.21(C)(1) through (C)(6)
If an overcurrent is 700 amperes, what is the approximate opening time of the OCPD? A. 0.02 seconds B. 2 seconds C. 20 seconds D. 100 seconds
B. 2 seconds
Match the correct Memory Word for each type of fuse...... Class T fuse A. rejection B. Tiny C. large D. junior
B. Tiny
Match the correct Interrupting Range for each type of fuse. -Class CF fuse A. 200kA B. 100KA C. 200kA or 300kA D. 10kA
C. 200kA or 300kA
Which of the following is/are a major source(s) of short-circuit current contribution? a. On-site generators b. Electric heating loads c. Utility source d. Both a. and c
d. Both a. and c
If a motor nameplate shows a service factor of 115%, the motor is designed to operate at ? its rated horsepower a. 1.15 times b. 0.115 times c. 115% d. both a. and c. e. none of the above
d. both a. and c.
It is necessary to select a separate overload protective device for a 25-horsepower continuous-duty motor with 32 amperes nameplate current rating and a marked 1.15 service factor. Table 430.250 shows 34 amperes for such a motor. What is the maximum trip setting or ampere rating permitted for this overload protective device? Assume that the more permissive requirements of 430.32(C) are not warranted. a. 32 A b. 34 A c. 40 A d. 42.5 A
c. 40 A
Match the correct Memory Word for each type of fuse...... Class J fuse A. Cube B. Tiny C. Large D. Junior
D. junior
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 2 (MDP) is ? . Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result a. 25,620 A b. 29,710 A c. 34,990 A d. 39,417 A
d. 39,417 A
Match the correct Interrupting Range for each type of fuse. -Class CC fuse A. 200kA B. 100KA C. 200kA or 300kA D. 10kA
A. 200kA
What is/are the most common interrupting ratings for current-limiting fuses? a. 50,000 A b. 100,000 A c. 200,000 A d. 300,000 A e. c. and d
e. c. and d
Match the correct Ampere Rating Range for each type of fuse. -Class CF fuse A. Fractional - 30A B. 1-100A C. 1/2 - 60A D. 1/8 - 600A
B. 1-100A
If a branch-circuit fuse is not marked with an interrupting rating, then the interrupting rating for that fuse is____? a. 1,000 A b. 5,000 A c. 10,000 A d. 50,000 A NEC reference??
c. 10,000 A NEC reference: 240.60(C)
Using the conductor sizing guide in this lesson, what conductor ampacity is needed for a 10-horsepower, 230-volt single phase motor? a. 50 A b. 60 A c. 62.5 A d. 87.5 A
c. 62.5 A
The percentage of current flow shown in the figure is approximately _____as compared to a 3-phase bolted fault current. A. 87% B. 89% C. 99% D. 25% to 125%
A. 87%
Match the correct Ampere Rating Range for each type of fuse. -Class CC fuse A. Fractional - 30A B. 1-100A C. 1/2 - 60A D. 1/8 - 600A
A. Fractional - 30A
The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s) best defines a(n) _____? a. branch circuit b. feeder c. service d. utility
A. branch circuit
Which of the following apply regarding the 10-foot tap rule where the ampere rating of the OCPD protecting the tap on the line-side connection is 250 amperes? a. Field installed tap conductors which leave the enclosure in which the tap was made, the tap conductor's ampacity is not less than 1/10th of the OCPD ampere rating that is protecting the feeder conductors. b. The ampacity of the tap conductor is not less than the ampere rating of the OCPD at the termination of the tap conductor, or is not less than the rating of the equipment containing an overcurrent protective device(s) supplied by the tap conductor. c. The ampacity of the tap conductor is not less than the calculated load of the loads supplied by the tap conductor. d. The tap conductors are enclosed in raceway if run external of an enclosure. e. All of the above
e. All of the above
As generally required in the NEC, match the overcurrent device ampere rating for the following small conductor sizes. 10AWG aluminum - A. 25 amperes B. 15 amperes C. 30 amperes D.20 amperes
A. 25 amperes
As generally required in the NEC, match the overcurrent device ampere rating for the following small conductor sizes. 12 AWG copper - A. 25 amperes B. 30 amperes C. 7 amperes D. 20 amperes
D. 20 amperes
An overcurrent that has current flow outside the normal conduction path could be a(n) _____? A. ground fault B. overload C. short circuit D. both A and C E. A, B, and C
D. both A and C
A 240-volt single-phase circuit using 4 AWG THW copper conductors and protected by an 80-ampere overcurrent device has an event where the circuit and load impedance results in a total resistance of 0.0024 ohms. Select the type of circuit condition occurring. A. ground fault B. normal operation C. overload D. short circuit
D. short circuit
When analyzing a short-circuit current, if the fault current level is equal above and below the zero axis of a sine wave, the fault current is ___ A. asymmetrical B. Different C. irregular D. symmetrical
D. symmetrical
Harmless overloads routinely are created by temporary inrush or surge current from which of the following? a. Energizing transformers b. Starting a motor c. Starting heating elements d. Resistive heater e. a. and b
E. A and B
T/F Interrupting ratings are required to be marked on supplemental protective devices. NEC reference??
False NEC reference: 240.83(C)
Under short-circuit conditions, which of the following represents an OCPD's level of thermal effect protection for circuit components? a. I2t b. Ip c. IT2 d. None of the above
a. I2t
Residual ground-fault protection monitors ground fault currents in the___? a. grounding strap b. neutral conductor c. phase conductors d. b. and c.
a. grounding strap
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short circuit at position 5 is ? than the short-circuit current at position 6 due to the shorter conductor run supplying LPB compared to the length of conductor supplying AC-1. a. higher b. lower
a. higher
The following 120-volt loads are connected to a 120-volt circuit using 12 AWG THWN-2 copper conductors and protected by a 20-ampere overcurrent device: L1 = 20 Ω, L2 = 12 Ω. The circuit condition is a(n) _____ A. ground fault B. normal operation C. overload D. short circuit
B. normal operation
T/F The voltage of an electrical system must be equal to or greater than voltage rating of an OCPD.
False
T/F Quite often, a circuit breaker will be marked with multiple voltage ratings and the corresponding interrupting ratings for each voltage rating, such as 600-volt 14 kA interrupting rating, 480-volt 22 kA, and 240-volt 42 kA.
True
T/F Per NEC 240.21, overcurrent protection shall be provided in each ungrounded circuit conductor and shall be located at the point where the conductors receive their supply except as specified in 240.21(A) through (H).
true
T/F When a short circuit occurs, running motors contribute four to six times their normal full load into the fault adding to the magnitude of the short-circuit current.
true
T/F High speed fuses can be used to provide motor branch-circuit short-circuit and ground-fault protection for motor branch-circuits with power electronic drives that provide circuit overload protection. NEC reference??
True NEC reference: 430.52(c)(5)
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 Use the single-phase formula for this calculation. The SCA at the beginning of the run is at panel LPA. The SCA from panel LPA must be multiplied by 0.5 (use 100% of the SCA at the transformer, 50%everywhere else for L-N or L-G) per Figure 3 Table procedure found in the Information Sheet of this lesson. Use 50% of the LPA SCA to calculate the "f" factor and 50% of the LPA SCA for the total for the total SCA.) The short-circuit current at position 9 (florescent luminaire) is ? . Note: Round to three decimal points for all calculations. The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result a. 434 A b. 1,067 A c. 1,367 A d. 10,100 A
b. 1,067 A
Which is not a performance requirement for a Class J, time-delay fuse (UL 248 Class J)? a. Have a voltage rating of 600 volts (AC) b. Have an interrupting rating of 200 kA (AC) or more c. Hold 500% inrush current for 10 seconds d. Must be resettable after fault interruption
d. Must be resettable after fault interruption
The purpose of overcurrent protection of capacitors is for____? a. delay sequence protection b. ground-fault protection c. overload protection d. short-circuit protection
d. short-circuit protection
In an industrial installation, three separate 400-ampere bus duct taps, each 40 feet in length, are permitted to be tapped from a 1,200-ampere busway protected by a 1,200-ampere OCPD. a. Acceptable b. Violation
a. Acceptable
Arcing faults create a very dangerous condition for Electrical Workers in close proximity to an arcing fault because of the tremendous amount of thermal energy emitted at the point of the fault. Which of the following is a recognized safe work practice to prevent serious worker injury or death? A. Working energized with heavy clothing and gloves B. Working on circuits which are listed to prevent bolted line-to-line faults C. Working on deenergized equipment under employer lockout/tagout procedure D. Working under the direction of an authorized employee
C Working on deenergized equipment under employer lockout/tagout procedure
Match the correct Interrupting Range for each type of fuse. -class L fuse A. 200kA B. 100KA C. 200kA or 300kA D. 10kA
C. 200kA or 300kA
If equipment draws a current of 300 amperes, what is the approximate opening time of the OCPD? A. 0.05 seconds B. 5 seconds C. 50 seconds D. 200 seconds
C. 50 seconds
If an OCPD opens in 12 seconds, approximately how much current was applied? A. 110A B. 200A C. 500A D. 2,000A
C. 500A
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short circuit at position 7 is ? than the short-circuit current at position 6 a. higher b. lower
b. lower
Listed current-limiting fuses have ____ features that help prevent the installation of fuses that cannot provide a comparable minimum protection level of critical ratings and performance a. current-limiting b. rejection c. resistance d. voltage surge protection
b. rejection
Using the fuse sizing guide, what are the two standard ampere ratings per 240.6 that could be selected for a dual-element time delay fuse sized for motor branch-circuit, short-circuit, and ground fault protection when there are separate overload relays intended for overload protection of a 10-horsepower, 230-volt, single phase motor? Be sure to review the ** and †† footnotes that are applicable. Assume that the permissive requirement of 430.52(C)(1) Exception 2 is not warranted. a. 50 A or 70 A b. 70 A or 80 A c. 70 A or 90 A d. 80 A or 90 A
d. 80 A or 90 A
What is/are the common operating function(s) that mechanical OCPDs share? a. Current/voltage interruption means b. Current-sensing means c. Unlatching mechanism d. All of the above
d. All of the above
Which of the following can be the benefits of current-limiting fuse applications? I. They are resettable II. They have high interrupting ratings, which prevent misapplication in high fault current applications III. They provide consistent, reliable overcurrent protection operation IV. They provide superior equipment short-circuit protection V. They require periodic calibration testing a. I. and II. b. I., II., III., IV., and V. c. I. and V. d. II., III., and IV.
d. II., III., and IV.
Generally, the overload element of a branch-circuit dual-element time-delay fuse will hold an overload that is five times greater than the ampere rating of the fuse for a minimum time of _____ a. 2 seconds b. 5 seconds c. 10 seconds d. 20 seconds
c. 10 seconds
The ground fault protection system shall be performance tested when first installed on site. What else is required as part of this performance testing? a. 230.95(C) requires GFPE to be performance tested when installed using the primary current injection test process. b. A written record of this test must be available to the authority having jurisdiction. c. The test shall be conducted in accordance with instructions that are required to be provided with the equipment. d. All of the above NEC reference??
d. All of the above NEC reference: 230.95(C)
Match the correct Memory Word for each type of fuse...... Class R fuse A. Large B. junior C. Rejection D. Cube
C. rejection
Match the correct Ampere Rating Range for each type of fuse. -Class J fuse A. 601-6,000A B. 1-100A C. 1/2 - 60A D. 1-600A
D. 1-600A
Match the correct Ampere Rating Range for each type of fuse. -Class R fuse (class RK5 and RK1 version) A. 601-6,000A B. 1/8-600A C. 1/2 - 60A D. 1/10-600A
D. 1/10-600A
Match the correct Ampere Rating Range for each type of fuse. -Class H fuse A. Fractional - 30A B. 1-100A C. 1/2 - 60A D. 1/8 - 600A
D. 1/8 - 600A
Match the correct Ampere Rating Range for each type of fuse. -Class L fuse A. 601-6,000A B. 1/8-600A C. 1/2 - 60A D. 601-6,000A
D. 601-6,000A
T/F Compare a 100-ampere Class RK1, a 100-ampere Class J, and a 100-ampere Class CF fuse, all 600-volt, dual-element, time-delay with 300 kiloamperes ratings. With few exceptions, all can be applied the same way, have similar characteristics, and are of the same dimensions.
False
T/F Ground faults on large ampacity services, such as 3,000 amperes, are always of the magnitude that the phase OCPD provides suitable protection against ground faults.
False
T/F Ground-fault protection can create selective coordination concerns depending upon the types and sizes of devices selected.
False
T/F There are fuses that provide visual open fuse indication. The majority of fuses sold commercially are fuses which do not provide any visual indication.
True
T/F Overcurrent protection shall be permitted to be installed as close as practicable to the storage battery terminals in an unclassified location. NEC reference??
True NEC reference: 240.21(H)
T/F Some fuses can be sized to provide both motor branch-circuit and short-circuit protection and also motor branch-circuit overload protection. NEC Reference?
True NEC reference: 430.55
A 25-foot, 4 AWG, 75°C, copper conductor could be tapped from a 3/0 AWG 75°C, copper feeder conductor protected by a 200-ampere OCPD, if the 4 AWG terminates in an 80 A OCPD and the tap conductors are protected from physical damage by being enclosed in an approved raceway a. Acceptable b. Violation
a. Acceptable
For this question, use the following criteria for the various Pt-to-Pt calculation step results in calculating the answers: Transformer full load current: round to a whole number, such as 601. Square root of 3: 1.732 f: three significant digits right of the decimal point, such as 1.036 transformer multiplier: three significant digits right of the decimal point M: three significant digits right of the decimal point Final calculated short-circuit current in amperes: round to whole number, such as 31,564. Determine the available short-circuit current with motor contribution on the 480/277 volt secondary of 500 kilovolt-amperes transformer which has 2% impedance. Assume motor contribution is 50% of the transformer rating. (Use 0.9 multiplier for %Z and assume primary of transformer has an infinite available short-circuit current. Select the answer closest to your calculated result. a. 33,889 A b. 34,591 A c. 40,645 A d. 43,890 A
b. 34,591 A
Which of the following is not a reason why short-circuit calculations are necessary for electrical systems? a. Analyze OCPDs for selective coordination. b. Determine the standard ampere rating of the OCPD. c. Ensure that OCPDs and components/equipment of a distribution system have adequate interrupting ratings and short-circuit current ratings. d. Service equipment is required to be marked with maximum available fault current.
b. Determine the standard ampere rating of the OCPD
The first step to determine the fault current at any point in the system is to draw a(n) ? showing all the sources of the short-circuit current. a. current path b. one-line diagram c. short-circuit path d. utility connection diagram
b. one-line diagram
The ground-fault protection provisions of 230.95 ? apply to a service disconnect for a continuous industrial process where a nonorderly shutdown will introduce additional or increased hazards. a. shall b. shall not
b. shall not
When calculating the multiplier for transformer short-circuit current, the transformer impedance (%Z) is multiplied by ? to determine the worst case condition to achieve the highest available short-circuit current. a. 0.09 b. 0.3 c. 0.9 d. 1.1
c. 0.9
Various methods have been developed to calculate the available short-circuit current. All are based on ___ . a. Lenz's Law b. current-limiting technology c. Ohm's Law d. Onderdonk Method
c. Ohm's Law
Which of the following is not a critical point where short-circuit calculations should be completed in a system? a. Industrial control panels b. Panelboards, motor control centers, transfer switches c. Push button device on 120 V control circuit d. Service entrance equipment
c. Push button device on 120 V control circuit
Indicate whether feeder taps of 20 feet are covered by each of the following NEC sections. 1. 240.21(A) 2. 240.21(B)(1) 3. 240.21(B)(2) 4. 240.21(B)(3) 5. 240.21(B)(4) 6. 240.21(B)(5)
1. 240.21(A) = not covered 2. 240.21(B)(1) = not covered 3. 240.21(B)(2) = covered 4. 240.21(B)(3) = covered 5. 240.21(B)(4) = not covered 6. 240.21(B)(5) = covered
For each type of fuse, identify whether it is current limiting, non-current limiting, or N/A (Not applicable). 1. Class CC fuse 2. Class CF fuse 3. Class G fuse 4. Class H fuse 5. Class j fuse 6. Class L fuse 7. Class R fuse 8. Class T fuse
1. current limiting 2. current limiting 3. current limiting 4. non-current limiting 5. current limiting 6. current limiting 7. current limiting 8. current limiting
Match the following with the proper UL standard. 1. insulated case circuit breakers 2. Low voltage power circuit breakers 3. Molded case circuit breakers 4. Motor circuit protectors 5. Supplementary protectors
1. insulated case circuit breakers - UL489 2. low voltage power circuit breakers- UL1066 3. molded case circuit breakers - UL489 4. motor circuit protectors - UL489 5. Supplementary protectors - UL1077
Match the correct Interrupting Range for each type of fuse. -Class R fuse (class RK5 and RK1 version) A. 200kA or 300kA(RK1) B. 100KA C. 200kA or 300kA D. 10kA
A. 200kA or 300kA(RK1)
As generally required in the NEC, match the overcurrent device ampere rating for the following small conductor sizes. 18 AWG copper A. 7 amperes B. 20 amperes C. 30 amperes D. 10 amperes
A. 7 amperes
As generally required in the NEC, match the overcurrent device ampere rating for the following small conductor sizes. 10 AWG copper - A. 25 amperes B. 30 amperes C. 7 amperes D. 20 amperes
B. 30 amperes
In a 480/277-volt 3-phase wye system, the arcing fault current range using older guidelines is approximately ____of the 3-phase bolted fault current. A. 87% B. 89% to 38% C. 125% to 25% D. none of the above
B. 89% to 38%
The speed of response of an OCPD when interrupting an overcurrent that is____ the OCPD's ampere rating can vary depending upon the magnitude of the overcurrent. a. equal to b. greater than c. less than d. all of the above
B. greater than
What electrical circuit condition best describes a phase or ungrounded conductor that comes into contact with another phase conductor or grounded conductor object? a. Overload b. Short circuit c. Too many loads connected to a circuit d. Ungrounded circuit
B. short circuit
The following 240-volt loads are connected to a 240-volt single-phase circuit using 4 AWG THW copper conductors and protected by an 80-ampere overcurrent device: L1 = 150 ohms, L2 = 200 ohms, L3 = 5 ohms, L4 = 3 ohms. The circuit condition is a(n) ______. A. ground fault B. normal operation C. overload D. short circuit
C. overload
An OCPD was caused to open in 0.01 seconds. What type of overcurrent most likely caused this OCPD device to open in this time? A. inverse time current B. overload C. short circuit D. time current curve
C. short circuit
The term branch circuit has different meanings as used in the NEC. Which of the following statement(s) is/are correct? a. A branch circuit is a type of circuit in an electrical distribution system connected from the final OCPD to the outlets and is not limited to the type of wiring method used. b. A category of overcurrent protective device used for services, feeders, branch circuits and equipment providing a full range of protection against short circuits, ground faults and overloads. c. Both a. and b. are correct. d. Neither a. nor b. is correct
C.Both a. and b. are correct.
The degree or magnitude of asymmetry of fault current depends upon ____? A. the point of time that fault occurs on the cycle B. The power factor of the faulted current C. The voltage of the system D. both A and B E. all of the above
D. both A and B
In addition to determining the proper OCPD ampere rating for an application, what criteria is/are important when selecting overcurrent devices? a. Interrupting rating b. Short-circuit current ratings c. Voltage rating d. All of the above
D.all of the above
T/F A branch-circuit overcurrent protective device that is current limiting will be marked "Current Limiting."
True
T/F For this question, use the following criteria for the various Pt-to-Pt calculation step results in calculating the answers: Transformer full load current: round to a whole number, such as 601. Square root of 3: 1.732 f: three significant digits right of the decimal point, such as 1.036 transformer multiplier: three significant digits right of the decimal point M: three significant digits right of the decimal point Final calculated short-circuit current in amperes: round to whole number, such as 31,564. Comparing the answers in the previous three questions, as the impedance in a transformer decreases, the short-circuit current available at the transformer secondary terminals increases. If the kVA of the transformer is higher, the short-circuit current available at the transformer secondary terminals is higher.
True
T/F New service equipment in commercial buildings must be field marked with the maximum available fault current and the date the calculations were performed.
True
Using Table 430.52, what is the maximum instantaneous trip circuit breaker setting allowed for the motor installation using a 460-volt, 25-horsepower, 3-phase motor marked with a 115% service factor and a nameplate current of 32 amperes based upon 430.32(A) and full-load current of 34 amperes in Table 430.250? a. 40 A b. 256 A c. 272 A d. 600 A
b. 256 A
If a branch-circuit circuit breaker is not marked with an interrupting rating, then the interrupting rating for that circuit breaker is ___? a. 1,000 A b. 5,000 A c. 10,000 A d. 50,000 A NEC reference?
b. 5,000 A NEC reference: 240.83(C)
UL Classes of fuses include branch-circuit fuses such as____ a. Class B, N, and C fuses b. Class L, J, and RK1 fuses c. Class slow blow and Class fast-acting fuses
b. Class L, J, and RK1 fuses
Which of the following is not a rating used when selecting overcurrent protective devices? a. Ampere rating b. Frame size c. Interrupting rating d. Voltage rating
b. Frame size
Under short-circuit conditions, which of the following represents an OCPD's maximum magnetic or mechanical force permitted to be exerted on circuit components and equipment? a. I2t b. Ip2 c. IT2 d. None of the above
b. Ip2
For this question, use the following criteria for the various Pt-to-Pt calculation step results in calculating the answers: Transformer full load current: round to a whole number, such as 601. Square root of 3: 1.732 f: three significant digits right of the decimal point, such as 1.036 transformer multiplier: three significant digits right of the decimal point M: three significant digits right of the decimal point Final calculated short-circuit current in amperes: round to whole number, such as 31,564. Calculate the short-circuit current at the transformer secondary terminals. The transformer is rated at 1,000 kilovolt-amperes, 3% impedance, 480/277 volt secondary, 3-phase. Use 0.9 multiplier for %Z transformer impedance ±10% tolerance. Do not include motor contribution. Select the answer closest to the calculated result. a. 34,600 A b. 38,985 A c. 44,556 A d. 51,345 A
c. 44,556 A
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 4 (LPC) is ? . Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result a. 5,890 A b. 10,052 A c. 13,203 A d. 25,385 A
d. 25,385 A
Size the maximum primary and secondary overcurrent devices for a 100-kilovolt-amperes, 3-phase transformer, a 480-volt primary, and a 208/120 volts secondary (Only consider the transformer and not conductor protection or panelboard protection). a. 100 A (primary) / 125 A (secondary) b. 175 A (primary) / 225 A (secondary) c. 250 A (primary) / 275 A (secondary) d. 300 A (primary) / 350 A (secondary)
d. 300 A (primary) / 350 A (secondary)
An OCPD category used to protect luminaires, appliances, and other equipment, but not permitted to be used as a substitute for required branch-circuit OCPDs or in place of the required branch-circuit protection best describes____. a. branch-circuit overcurrent protection b. equipment overcurrent protection c. selective coordination of overcurrent protection d. supplementary overcurrent protection
d. supplementary overcurrent protection
T/F A circuit breaker with a special "straight" rating of 277/480 volts may be used on a corner-grounded delta system.
False
T/F A fuse or circuit breaker that is permitted for branch-circuit overcurrent protection is required to be marked "branch-circuit fuse," "branch-circuit breaker," or "branch-circuit overcurrent protective device."
False
T/F All circuit breaker are required to have their ampere ratings marked on the circuit breaker handle or escutcheon.
False
T/F Fuses have straight and slash voltage ratings.
False
T/F Supplementary OCPDs are described as OCPDs permitted for only specific branch-circuit applications, under limited conditions, per the specific reference in the NEC.
False
T/F An arcing fault current is always less than the available bolted fault current value at a specific location.
True
T/F NFPA 70E 225.3 Circuit Breaker Testing states that "Circuit breakers that interrupt faults approaching their ratings shall be inspected and tested in accordance with the manufacturer's instructions."
True
T/F The operating mechanism, including the handle, opens or closes the circuit breaker contacts.
True
T/F When a non-current-limiting OCPD permits fault current to flow for 11/2 cycles during a high short-circuit current condition, the circuit wiring and components must endure tremendous amounts of thermal and magnetic energy.
True
T/F Service equipment in commercial installations is required to be field marked with the maximum available fault current and date of fault calculations.
True NEC reference: 110.24(A)
T/F Ampere rating, voltage rating, interrupting rating where other than 10,000 amperes, current limiting where applicable, and the name or trademark of the manufacturer are all items which must be plainly marked on the barrel of a fuse. NEC reference????
True NEC reference: 240.60(c)
Under short-circuit current conditions, which OCPD provides better short-circuit protection for conductors and other components? a. OCPD #1 let-through data: Ip = 12,000 A and I2t = 60,000 A2 seconds b. OCPD #2 let-through data: Ip = 70,100 A and I2t = 20,750,000 A2 seconds
a. OCPD #1 let-through data: Ip = 12,000 A and I2t = 60,000 A2 seconds
If a conductor's ampacity does not correspond to a standard circuit breaker or fuse ampere rating found in___ ,____ permits selecting the next standard ampere rating if specific conditions in ___ are met. a. 240.1 / 240.6 / 240.21 b. 240.15(A) / 240.21 / 240.4(B) c. 240.6 / 240.4(B) / 240.4(B) d. 240.24 / 240.4(C) / 240.4(B)
c. 240.6 / 240.4(B) / 240.4(B)
Straight voltage rated circuit breakers of the proper voltage rating (the volt rating is greater than system line-line voltage) are allowed to be used on which of the following voltage systems? I. 120 V 1 Ø, 2 W, solidly grounded II. 120/240 V 1 Ø, 3 W, solidly grounded III. 208 Y/120 V 3 Ø, 4 W, solidly grounded IV. 240 V 3 Ø, 3 W, ungrounded or corner grounded delta V. 480 Y/277 V 3 Ø, 4 W, solidly grounded VI. 480 V 3 Ø, 3 W, ungrounded or high resistance grounded VII. 600 Y/347 V 3 Ø, 4 W, solidly grounded VIII. 600 V 3 Ø, 3 W, solidly grounded a. II. and III. b. II., III., IV.,V., and VI. c. All voltage systems above apply d. Straight voltage rated circuit breakers are not to be use NEC reference???
c. All voltage systems above apply NEC reference: 240.85
T/F Supplementary fuses used to protect individual luminaires, appliances, or control circuits are allowed to be considered as the final branch-circuit overcurrent protective device. NEC reference??
False NEC reference: 240.10
T/F Conductors, other than flexible cords, flexible cables, and fixture wires, are required without exception or other permission to be protected against overcurrent in accordance with their ampacity specified in 310.15 at the source connection point of the conductor NEC reference??
False NEC reference: 240.4
As generally required in the NEC, match the overcurrent device ampere rating for the following small conductor sizes. 12 AWG aluminum - A. 25 amperes B. 20 amperes C. 30 amperes D. 15 amperes
D. 15 amperes
T/F Per the second paragraph of 110.9, devices such as motor starters and switches must have interrupting ratings at applied voltage sufficient for the available short circuit at its line terminals.
False
T/F Short-circuit calculations are performed without overcurrent protective devices in the system. Calculations are done as though these devices are replaced with copper bars to determine the available short-circuit current.
True
T/F Supplementary protective devices can only be used as additional protection when installed on the load side of a branch-circuit overcurrent device.
True
T/F The characteristic of the operating mechanism in using the handle to open or close a circuit breaker is referred to as quick-make, quick-break as to prevent the breaker from being able to be "teased" from OFF-to-ON or ON-to-OFF.
True
For this question, use the following criteria for the various Pt-to-Pt calculation step results in calculating the answers: Transformer full load current: round to a whole number, such as 601. Square root of 3: 1.732 f: three significant digits right of the decimal point, such as 1.036 transformer multiplier: three significant digits right of the decimal point M: three significant digits right of the decimal point Final calculated short-circuit current in amperes: round to whole number, such as 31,564. Calculate the short-circuit current at the transformer secondary terminals of a transformer rated 750 kilovolt-amperes, 1.5% impedance, 480/277 volt secondary, 3-phase. Use 0.9 multiplier for %Z transformer impedance -10% tolerance. Do not include motor contribution. Select the answer closest to the calculated results a. 66,815 A b. 69,018 A c. 89,037 A d. 115,778 A
a. 66,815 A
For this question, use the following criteria for the various Pt-to-Pt calculation step results in calculating the answers: Transformer full load current: round to a whole number, such as 601. Square root of 3: 1.732 f: three significant digits right of the decimal point, such as 1.036 transformer multiplier: three significant digits right of the decimal point M: three significant digits right of the decimal point Final calculated short-circuit current in amperes: round to whole number, such as 31,564. Calculate the short-circuit current at the transformer secondary terminals of a transformer rated 1,000 kilovolt-amperes, 1.5% impedance, 480/277 volt secondary, 3-phase. Use 0.9 multiplier for %Z transformer impedance -10% tolerance. Do not include motor contribution. Select the answer closest to the calculated results a. 89,111 A b. 95,566 A c. 100,190 A d. 105,289 A
a. 89,111 A
A 3/0 AWG copper feeder conductor is tapped with 20 feet of 2 AWG conductor. What is the maximum OCPD size allowed at the termination of the tap conductors installed in a fused switch or circuit breaker? (All conductors and terminations are rated 75°C.) a. 100 A b. 110 A c. 125 A d. 150 A
b. 110 A
Per NEC ? , the overcurrent protective devices, the total impedance, the component short-circuit current ratings, and other characteristics of the circuit to be protected shall be selected and coordinated to permit the circuit protective devices to clear a fault to do so without extensive damage to the electrical components of the circuit. a. 110.9 b. 110.10 c. 110.16 d. 110.22
b. 110.10
According to 430.32, if a continuous-duty motor nameplate does not have a 1.15 or greater service factor or temperature rise of 40°C or less, then a separate overload protection device must be set at no more than ? (assuming that this selection will permit the motor to start and that sizing per 430.32(C) is not warranted). a. 100% b. 115% c. 125% d. 135%
b. 115%
A panelboard that is located downstream from a service disconnect is calculated to have 45,000 amperes of available fault current. A circuit breaker installed in this downstream panel must have an interrupting rating equal or greater than ____? a. 10,000 A b. 25,000 A c. 30,000 A d. 45,000 A
d. 45,000 A
Refer to the figures and follow the steps outlined in the short-circuit calculation procedure.Calculation of Fault Currents - Figure 10Calculation of Fault Currents - Figure 11 The short-circuit current at position 7 (AC-2) is ? . (Note: AC-1 and AC-2 are 3-phase, L-L-L loads. They do not require a neutral conductor to operate.) Note: The values calculated for this question will be used for additional questions. Select the answer closest to your calculated result a. 4,507 A b. 6,892 A c. 7,895 A d. 9,815 A
d. 9,815 A
Which are branch circuit rated circuit breakers? I. Instantaneous (only)circuit breaker II. Insulated case circuit breaker III. Low-voltage power circuit breaker IV. Molded case circuit breaker V. Supplementary circuit breaker a. I., II., and IV. b. I. and III. c. II. and V. d. II., III., and IV. e. III., IV., and V. f. V. only
d. II., III., and IV.
Which of the following is/are reasons that explain why there are numerous types of circuit breakers available? I. Each type offers different features and benefits II. Multiple interrupting ratings III. Multiple overcurrent sensing type and adjustable current-time parameters IV. Multiple voltage ratings V. Numerous frame and ampere ratings VI. Price VII. Variety of circuit breaker dimensions a. I. only b. II. and III. c. VI. and VII. d. VII. only e. All of the above
e. All of the above
A motor circuit protector (MCP) or instantaneous trip circuit breaker is a device that ___? a. has only an instantaneous trip b. is part of listed combination with specific starter(s) c. is UL recognized d. provides no overload protection e. all of the above
e. all of the above
T/F Supplementary overcurrent protection is used for luminaires, appliances, and other equipment and can be used as a substitute where branch-circuit overcurrent devices are required.
false
T/F When a fuse or circuit breaker interrupts a short-circuit current exceeding its interrupting rating, the UL product standards require that an indication pin on the fuse or circuit breaker actuate so that the Electrical Worker knows to replace the device with a new OCPD with an adequate interrupting rating.
false
Slash voltage rated circuit breakers of the proper voltage rating are allowed to be used on which of the following voltage systems? I. 120 V 1 Ø, 2 W, solidly grounded II. 120/240 V 1 Ø, 3 W, solidly grounded III. 208 Y/120 V 3 Ø, 4 W, solidly grounded IV. 240 V 3 Ø, 3 W, ungrounded or corner grounded delta V. 347 V VI. 480 Y/277 V 3 Ø, 4 W, solidly grounded VII. 480 V 3 Ø, 3 W, ungrounded or high resistance grounded VIII. 600 Y/347 V 3 Ø, 4 W, solidly grounded IX. 600 V 3 Ø, 3 W, ungrounded or high resistance grounded a. I., II., and III. b. I., II., III., VI., and VIII. c. All voltage systems above apply d. Slash voltage rated circuit breakers are not to be used
b. I., II., III., VI., and VIII.
A(n) ___is best defined as any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload or short circuit a. branch-circuit overcurrent device b. overcurrent c. overload d. supplementary overcurrent device
B. overcurrent NEC Reference: 100
T/F Where supplementary overcurrent protection is used for luminaires, appliances, and other equipment or for internal circuits and components of equipment, it shall be permitted to serve as a substitute for required branch-circuit overcurrent devices or in place of the required branch-circuit protection. NEC reference??
False NEC reference: 240.10
The long-time pick-up (LTPU) and long-time delay (LTD) determine the overload protection characteristics of an adjustable electronic circuit breaker. The typical adjustment range for the LTPU is from ____times the circuit-breaker ampere rating. a. 0.25 to 0.5 b. 0.5 to 1.0 c. 1.0 to 1.5 d. 1.5 to 2.0
b. 0.5 to 1.0
Under fault conditions, the greatest damage done to components by a fault current often occurs in the first half-cycle. What are the most common results of a fault current to electrical components? a. Explosive vaporization of the metal conductors and conductive parts b. Heating of components to high temperatures can cause deterioration of insulation c. Tremendous magnetic forces between conductors can crack insulators and loosen or rupture bracing structures or equipment. d. both a. and b. e. a., b., and c.
e. a., b., and c.
T/F Branch-circuit fuses or circuit breakers, 600 volts or less, that are marked "current-limiting" have met specific current-limiting performance requirements per its respective product standard.
true
T/F Low-voltage power circuit breakers are the most rugged, highest priced, and largest size circuit breakers and are used in larger ampacity circuits in main switchgear and unit substations
true
T/F Overcurrent protective devices have product standards which establish requirements for certain minimum product performance criteria and physical specifications. UL 248 is a fuse product standard and UL 489 is a molded case circuit breaker product standard.
true
