Chapter 30 powerpoints Flashcards
Commercial buildings require high levels of power for:
Lighting
Motors
Heating elements
Other loads
Different size _______________ are used depending on the amount of power required and the type of loads.
power distribution systems
Relatively low voltage levels:
Used for small commercial applications by the local utility.
Like gas stations, restaurants.
208 V to 240 V
Medium voltage levels:
- Used for mid-sized commercial applications.
- Like small office buildings.
460 V to 480 V
Used for large commercial applications
Like colleges, small businesses, hotels
Voltages must be delivered and distributed to different transformer banks throughout a building
High levels: 1000 V and up
an assemblage of equipment installed for switching, changing, or regulating the voltage of electricity. Where high voltage is reduced.
Substation
The exact voltage level used to operate different loads in commercial applications depends on:
The loads
The given application
The NEC
NEC limits the voltage level to 120 V between conductors that supply:
Lighting fixtures, cords, and plugs that connect loads up to 1440 VA (volt-amperes)
Motors up to ¼ HP in dwelling units and guest rooms of:
Hotels
Motels
Similar rooms of occupancies
Commercial power needs include the same needs as residential _______________.
(1Φ) and industrial (3Φ) systems
Commercial customers use low-voltage _______ and ______.
3Φ and 1Φ power
Power companies use _________ to deliver power to customers through different distribution systems.
transformers
Primarily use________ connected in different combinations to deliver the correct power.
1Φ transformers
The distribution system used varies based on the _________.
application
Common commercial distribution systems include:
120/240 V, 1Φ, 3-wire
120/208 V, 3Φ, 4-wire
120/240 V, 3Φ , 4-wire
277/480 V, 3Φ, 4-wire
All ________________ read a voltage between the conductor and a ground point (grounded conduit, green ground wire, et c.)
ungrounded (hot) conductors
The voltage on the ___________ of a transformer begins to drop if the transformer is overloaded. The higher the overload, the greater the voltage drop
secondary side
This is the primary serviced used to supply most residential buildings.
Distribution Systems: 120/240 V, 1Φ, 3-Wire Service
In commercial wiring, small appliance usage includes more than typical _____________.
residential small appliance usage
Three-phase circuits include three individual __________________.
ungrounded (hot) powerlines
- Is used to supply customers that require:
- A large amount of 120 V, 1Φ power
- Low-voltage 3Φ power
- Includes three ungrounded (hot) lines and one grounded (neutral) line.
- Each hot line has 120 V to ground when connected to the neutral line
Distribution Systems: 120/208 V, 3Φ, 4-Wire Service
Is used to supply customers that require large amounts of:
3 Φ power with some 120 V
240 V, 1 Φ power
Distribution Systems: 120/240 V, 3 Φ, 4-Wire Service
Is the same as the 120/208 V, 3Φ, 4-wire service except the voltage levels are higher. Includes three ungrounded (hot) lines and one grounded (neutral) line.
277/480 V, 3Φ , 4-Wire Service
Voltage Variation Effects on AC Motors are?
All motors are designed to operate at the given voltage. A motor operates if the voltage varies below or above the rated voltage. Is a change in the motor’s performance.
Any variation in applied ________ to a heating element increases or decreases the amount of heat produced.
voltage
The voltage on incandescent lamps can vary from _____________ than the lamp’s rated voltage.
0V to 10% higher
Conductors are covered with insulating material. Available in ____________
The function of each conductor can by easily determined.
different colors
Never assume that conductors are properly marked or color-coded. Take _____________ to ensure that voltage is off before working on a circuit.
voltage measurements
Conductor Identification- Color Coding
Always use standard colors
always indicates a conductor used for grounding in the electrical field
Green
may be used to indicate a hot wire in a 230 V circuit or switched wire in a 115 V circuit.
Red
is used for the neutral conductor
White or natural gray
a current-carrying conductor that is intentionally grounded
Neutral conductor
Hot conductors in a ______ may be identified with other types of markings in addition to color coding.
3Φ system
a preprinted peel-off marker designed to adhere when wrapped around a conductor. May be used in place of tape bands.
Wire marker:
may be used in commercial rooms to automatically turn OFF lights when no one is present and automatically turn ON lights when a person enters the room.
Passive infrared wall switch sensors
Outdoor commercial lighting systems may use what type of lamps?
Low or high-pressure sodium, metal-halide, or mercury-vapor lamps
Outdoor commercial lighting systems have voltages of:
In voltages of 120V, 280V, 240V, 277V or 480V.
Outdoor commercial lighting systems have power ratings of……
35W to above 1500W.
Indoor commercial lighting systems are required for:
- All general rooms of occupancy
- Halls
- Restrooms
- Work areas
Indoor commercial lighting systems my use hat types of lamps?
Incandescent, halogen, or fluorescent lamps
What are the typical voltages for indoor commercial lighting?
In voltages of 120V, 208V, 220V, 240V, or 277V
Power rating for indoor commercial lighting range from what?
Any size up to 300 W for incandescent
15W to 215 for fluorescent
the unit used to measure the total amount of light produced by a light source
Lumen (lm)
the effect that occurs when light falls on a surface
Illumination
the amount of light produced by a lamp (lumens) divided by the area that is illuminated.
Footcandle (fc)
the perceived amount of light reflecting from an object
Brightness
an electric lamp that produces light by the flow of current through a tungsten filament inside a sealed glass bulb sometimes filled with gas. The most widely used lamps in the world
Incandescent lamp
a conductor with a resistance high enough to cause the conductor to heat.
Filament
should be used in environments that contain corrosive materials (salt water, oil, sulfuric acid, steam, sodium hydroxide, hydrochloric acid, et c.)
Fiberglass-reinforced lamp fixtures
The ____ of an incandescent lamp holds the lamp firmly in the socket and connects electricity from the outside circuit to the filament.
base
Bulb sizes and shapes are determined by the end use of the lamp.
Incandescent bulb size/shape
The size of an incandescent lamp is determined by the ________ of the lamp’s bulb.
diameter
With incandescent bulbs the diameter of a bulb is expressed in _______________.
eighths of an inch (1/8”)
a unit of power equal to the power produced by a current of 1 A across a potential difference of 1V.
Watt (W):
Incandescent Lamps: Lamps Sizes and Ratings. To calculate power, apply the following formula:
P = E x I Where P = power (in W) E= voltage (in V) I = current (in A)
an incandescent lamp filled with a halogen gas (iodine or bromine). The gas combines with tungsten evaporated from the filament as the lamp burns.
Tungsten-halogen lamp:
In Tungsten-halogen lamps wattages range from.
15W to 1500W
a low-pressure discharge lamp in which ionization of mercury vapor transforms ultraviolet energy generated by the discharge into light. Consists of a cylindrical class tube (bulb) sealed at both ends.
Fluorescent Lamps
tungsten coil coated with electron-emissive material that releases electrons when heated.
Cathode
a fluorescent lamp that has a smaller diameter than a conventional fluorescent lamp and a folded bulb configuration.
Compact fluorescent lamp
Cool white or light white fluorescent bulbs produce a ___________.
pale blue-green whiteness
White fluorescent bulbs produce a very ___________. May also be labeled as natural or daylight.
pale yellow-whiteness
produce a more yellow-whiteness.
Are used to give a warm feeling and enhance brighter colors.
Suggested for low lighting levels.
Warm, white fluorescent bulbs
a fluorescent lamp-starting circuit that heats the cathode before an arc is created. Used in some low-wattage lamps (4W to 20W). Common in desk lamps.
Fluorescent lamps Pre-heat circuit.
a fluorescent lamp-starting circuit that provides sufficient voltage to strike an arc instantly.
Instant-start circuit
a fluorescent lamp-starting circuit that has separate windings to provide continuous heating voltage on the lamp cathodes.
Rapid-start circuits
a lamp that produces light from an arc tube.
High-intensity discharge lamps
the light-producing element of an HID lamp.
Arc tube
the appearance of a color when illuminated by a light source.
Color Rendering
Low-pressure sodium lamps are good for outdoor lighting installations
High-Intensity Discharge Lamps: Selection
an HID lamp that operates at a low vapor pressure and uses sodium as the vapor.
Low-pressure sodium lamp:
an HID lamp that produces light by an electrical discharge through mercury vapor.
Mercury-vapor lamp:
an HID lamp that produces light by an electrical discharge through mercury vapor and metal halide in the arc tube.
Metal-halide lamp
