ELT150.I60 Industrial Wiring
What is the vertical distance from the manhole rim to the first floor of the industrial building?
0.64
Feeder busway sections are available in standard ____-ft lengths and in other lengths on special order.
10
What is the vertical distance from the manhole rim to the first floor of the industrial building, measured in feet and inches accurate to 1⁄16 inch?
10/16 of an inch
The industrial trolley bus is a ____-ampere, enclosed busbar electrical system.
100
Panelboards are available with standard main ratings of 100, 225, 400, 600, 800, and ____ amperes.
1200
Bus drop safety springs are used to maintain the proper tension on the horizontal and vertical cord runs. These springs are available with 40-, 80-, and ____-pound ratings.
150
A 600-volt to 200-volt transformer would become a 600-volt to ____-volt transformer if the connections were reversed.
1800
What is the difference, in SI units, between the lowest and the highest contours?
2.134 meters
As a general rule, a panelboard for which more than 10 percent of its overcurrent devices are rated at ____ amperes or less, and for which neutral connections are provided, is defined as a lighting and appliance branch-circuit panelboard.
30
If the primary current is less than two amperes for a transformer rated at 600 volts or less, the short-circuit protective device can be set at not more than ____ percent of this value.
300
The voltage ratings of the breakers must be higher than that of the system. Breakers are usually rated at 250 or ____ volts.
600
Refer to plan E1 on page 2 of the plans. What is the height of the boiler room floor?
743.5
What would be the elevation, at the pole, of the bottom of a trench being dug to install telephone service using rigid nonmetallic conduit?
743.5
It was determined that the rigid nonmetallic conduit for the telephone service could be installed in a trench with a bottom elevation of 743.65 ft. If the conduit is allowed to rise a distance of 1 ft, how deep is the trench at the building?
744.65
What is the elevation of the manhole rim where the benchmark is established?
745.66
What is the elevation of the first floor of the industrial building?
746.3
The autotransformer is designed to provide voltage components to the potential coils of the reactive meter. These voltage components are ____ degrees out of phase with the line voltage.
90
What device is generally used to measure length on a plot or building plan?
A Scale
What is the procedure for terminating an incoming high-voltage cable?
A device called a pothead provides a reliable method of terminating a high-voltage cable,
Explain the difference between a soft metric conversion and a hard metric conversion.
A soft conversion is an exact conversion where the material dimension has not changed and a hard conversion is used in the building industry to make the metric units more rational
Connections between the current and potential transformers in the high-voltage section of the unit substation and the autotransformer and meter sockets in the cabinet are made with size 12 ____ wire.
American Wire Gauge
____ provide branch-circuit protection for each of the machines in the manufacturing area of the plant.
Bus plugs
What is the role of center feed-in boxes?
Center feed-in boxes are used to bring the electrical supply cables to the trolley busway.
____ cubicles are used to connect the No. 2 feeder busway to the 225-ampere, plug-in busway runs.
Circuit-breaker
____ is the process of selecting protective devices so that there is a minimum of power interruption in case of a fault or overload.
Coordination
High-voltage fuses are available with either an N or a(n) ____ rating.
E
When planning or diagramming a floor-mounted transformer supplying a power panelboard, what are important components to include?
Feeder busways, cable tap box, primary fused switch, the transformer, the power panelboard, motor controllers, conduits to motors, secondary feeder protections, wireways.
What rules should be followed to set the magnetic trip?
In general, a low setting may be ten or twelve times the overload trip rating. Two rules should be followed whenever the magnetic trip is set: The lower setting provides the greater protection. The setting should be lower than the value of the short-circuit current available at that point.
A cable containing two insulated conductors and a bare grounding wire is installed to a lighting standard mounted on a base similar to the one shown in Figure 1-23. Assume you are the electrician in charge. What instruction would you give to a first-year apprentice who will make up the grounding connection?
It is mandatory that all conductive parts, including the grounding electrode, base, bolts, and conduits, be bonded together to achieve comprehensive grounding.
Describe the information in NEC Table 310.4(A), which specifies types of insulation.
It lists the temperature rating of insulation types for specific conductor materials and then gives the wire size allowed by ampacity rating of that conductor.
____ clamp hangers eliminate the drilling, cutting, or bending generally associated with hangers constructed on the job.
Prefabricated
How are plug-in busways suspended?
Prefabricated clamp hangers eliminate the drilling, cutting, or bending generally associated with hangers constructed on the job. Clamp hanger halves are slipped over the duct casing and are bolted together
Why is it necessary to have a good grounding system for the building?
Proper grounding protects circuits and equipment from destruction and personnel from injury.
What role do taps play?
Taps provide a way of making small changes to the turns ratio in the transformer.
What are the three most common methods of determining ground resistance?
The Wenner The fall of potential and the clamp on
Which of the methods for measuring ground resistance is used to measure resistance over a wide area?
The Wenner four-point test
Describe the circuit-breaker cubicle.
The circuit-breaker cubicle consists of a cube-shaped steel housing. This housing can be attached to the lower side of the ventilated feeder duct. Two 225-ampere circuit breakers are provided in a single housing. Openings in the sides of the cubicle permit the attachment of a plug-in busway
According to the NEC, what five conditions must be met when conductors are in parallel?
The conductors must be of the same length. The conductors must be made of the same material. It is not permissible to use copper for one conductor and aluminum for the others. The conductors must have the same circular mil area. The conductors must use the same type of insulation. The conductors must be terminated and connected in the same manner.
What is an additional role of connecting busways to enclosures such as unit substations?
The connection of the busway to enclosures such as unit substations is accomplished with flanged end connections. In addition, these connections are used to transpose the positions of the buses connected to the same phase, this transposition reduces the impedance of the total length of the busway. Because each phase is located at two places (or more in larger busways), the effects of the magnetic field are reduced, and the opposition to the current flow is also reduced
Describe the luminaires used in the manufacturing area.
The general illumination system for the manufacturing area of the plant consists of 180 fluorescent luminaires suspended from a system of 50-ampere lighting trolley busways
Discuss the role and location of the grounding bus.
The majority of the connections to ground are made in the low-voltage section however the grounding bus usually runs the entire length of the unit substation. This bus provides the means for a positive ground connection between the compartments, as well as a convenient place to make other ground connections.
What requirements should be followed for lighting and appliance panelboards?
The panelboard shall have a rating of not less than the minimum feeder capacity as calculated according to 408.30. The panelboard must be protected using an overcurrent protective device with a trip setting not exceeding the rating of the panelboard. The total 3-hour load shall not exceed 80% of the panelboard rating except when specifically rated for 100% continuous duty.
How are bus plugs selected?
The plug-in unit size is based on the switch ampere rating
What should the selection of a circuit breaker be based on?
The selection of the circuit breaker should be based on the necessity t0 provide the proper overload protection; ensure a suitable voltage rating; provide a sufficient interrupt current rating; provide short-circuit or ground-fault protections; and coordinate the breaker(s) with other protective devices.
How do you select a fuse with the correct continuous current rating to provide transformer protection?
The selection of the fuse with the correct continuous current rating to provide transformer protection is based on the following recommendations: select a fuse with the lowest rating that has a minimum melting time of 0.1 second at 12 times the continuous current rating of the transformer; select a fuse with a continuous current rating of 1.6 times the continuous current rating of the transformer; select a fuse that complies with NEC Article 450.
In a set of construction drawings, where would an electrician find information about the location and placement of a building?
The site plan by referring to existing points such as the centerline of a street or property lines
An aluminum wire 2250 feet long cannot have a resistance greater than 0.2 ohm. What is the minimum size wire (in circular mils) that may be used?
The smallest acceptable standard conductor size is 4/0 AWG.
From information on the Composite Site Plan, where is the lowest area on the site and what is the elevation?
The south east corner 745
How is a 4-wire rubber cord used with trolleys?
The trolleys have six graphite bronze shoes. These shoes make contact with the busbars and provide a path that continues through the fuse cutout and receptacle to the heavy-duty, 4-wire rubber cord. This cord is used to attach the various portable tools such as electric drills, buffers, grinders, and other equipment to the busway system, The 4-wire rubber cord provides three conductors to operate the 3-phase portable tools used on the job. The fourth conductor (green in color) is used to ground the equipment
The 50-ampere lighting circuits used in the trolley systems are approved by ____.
Underwriters Laboratories
Why is the structure of cord grips important?
When strain or tension is placed on the rubber cord so that it is pulled taut, the basket structure of the cord grip contracts to apply a stronger grip on the cord
What advantages does a suspended lighting system have?
a system of luminaires suspended from a trolley system can be readily shifted from one location to another as desired. It is not necessary to take down or replace heavy conduit systems as would be required to change a fixed lighting outlet system. If extensive alterations or a major plant changeover requires the removal of the lighting trolley duct, the duct sections are completely reusable.
What is the common name used by electricians for the assembly properly known as a busway?
bus duct
After the incoming voltage is reduced to the desired value, it is taken by ____ into the low-voltage section.
busbars
The trip rating of the circuit breaker cannot exceed the ampacity of the ____ in the panelboard.
busbars
What should you be wary of when coordinating high-voltage fusings?
circuit breakers that are used as secondary protective devices, and a single main protective device that is installed on the secondary side of the transformer.
The trolley busway is equipped with two ____ busbars.
copper
Straight sections, elbows, tees, and ____ are standard components available for use so that ducts can be installed horizontally or vertically, edgewise or flat, and can meet any turn or elevation requirements.
crosses
A ____ section provides the means for removing or inserting trolleys. This section contains two hinged doors that open when a lever is raised.
drop-out
When a subfeeder serves more than one panelboard, then connections must be made in the subfeeder for ____.
each panelboard
What are the possible structures of plug-in busway fittings?
ells, tees, and cross sections
Two single-pole breakers require installation space ____ that of a double-pole breaker.
equal to
The power supply from the panelboard is fed into a busway run through a ____.
feed-in adapter
Busways held up by cables must all be supported at intervals of ____ ft or less.
five
A lighting system composed of ____ outlets and a ____ conduit system is not easily adaptable to changing requirements.
fixed
The connection of the busway to enclosures such as unit substations is accomplished with ____.
flanged end connections
An alternative to grounding the secondary is to let it ____; that is, the secondary remains ungrounded.
float
The main for a panelboard may be either a(n) ____ or a circuit breaker.
fuse
Commonly, 4-conductor type SJ rubber cords are used to connect various machines; the colors of the individual conductors of the cord are black, white, red, and ____
green
Power can be tapped from the feeder busway at any ____ opening.
handhole
If there is any question as to the exact value of the short-circuit current available at a point, a circuit breaker with ____ interrupt rating is to be installed.
high
Rate reductions are made by the power company when the metering measurements are taken on the ____ side of the transformer.
high-voltage
The decimal impedance in a transformer is found by determining the ratio of the variable source voltage as compared to the rated voltage of the ____ winding.
high-voltage
Luminaires are equipped with ____, which cause the lamps to fire at different times.
lead-lag adders
Briefly discuss panelboard installations that do not require a main protective device and then outline situations in which individual protection is required.
lighting and appliance panelboards Panelboards are available with standard main ratings of 100, 225, 400, 600, 800, and 1200 amperes. These panelboards may be installed without a main protective device and can be connected directly to a feeder protected at not more than the rating of the panelboard. Individual protection is required on lighting and appliance panelboards when these panelboards are connected to the secondary of a transformer having only primary protection.
Lightning arresters are designed to provide a(n) ____ path to ground for any surge currents such as those resulting from a lightning strike.
low-impedance
The temperature rating of conductors must be selected and coordinated after consideration of the ____ of any connected termination, conductor, or device.
lowest temperature rating
Adjustments of the ____ determine the degree of protection provided by the circuit breaker if a short circuit occurs.
magnetic trip
The rates charged by the power company for the energy used are based on the readings of the meter registers and the ____ indicators.
maximum demand
If subfeed lugs are used, the electrician must ensure that the lugs are suitable for making ____.
multiple connections
Circuit control and ____ protection must be provided for all circuits and the power-consuming devices connected to these circuits.
overcurrent
The plug-in busway is much like a ____ extending through a complete load area.
panelboard
The lighting trolley is available in 5-ft (1.5-m) and 10-ft (3-m) sections, which are joined by ____ couplings.
plain
The equipment attachment plugs used with the duct system are ____, which eliminates several problems when portable tools having three-phase motors are used.
polarized
The couplings joining lighting trolley sections make a ____ connection, electrically and mechanically, between two duct sections and permit free passage of the trolleys along the duct runs.
positive
A device called a ____ provides a reliable method of terminating a high-voltage cable.
pothead
Panelboards that are not lighting panelboards are known as ____ or distribution panelboards.
power
The ____ of a transformer is the winding that is connected to a voltage source.
primary
The only tool needed to join the industrial-type trolley duct is a ____.
screwdriver
The busbars in the busway are coated with ____ at each connection point since it is unequaled as an electrical conductor.
silver
What shape are the standard segments used to construct trolley systems?
straight
The plug-in unit size of a bus plug is based on the ____.
switch ampere rating
Tapoff openings every ____ inches along the plug-in busway mean that there is always a convenient location to connect a machine.
ten
In general, in a circuit breaker, a low setting may be ____ times the overload rating.
ten to twelve
Where is the preferred area for location of the construction trailer? Why did you choose that area
the southeast corner of the site because there is nothing that is to be done to that section of the site
For a three-pole circuit breaker, ____ pole(s) is (are) required for each breaker used.
three
Messenger wires supporting the trolley lighting circuit are adjusted for tension by ____ located at the ends of the runs.
turnbuckles
For feeder busway No. 2, rated at 1600 amperes, what is the current density in busbars with cross-sectional area of 394 square millimeters?
two amperes/mm2
The step-down transformers, metering, and switching equipment necessary to supply the low voltage loads to the customer are housed in a ____.
unit substation
n feeder busway No. 2, ____ snap-on covers insulate the bolted busbar sections.
vinyl plastic
