electrical Flashcards
- phenomenon; manifestation
- Principally made up of atoms (electron, proton, neutron)
Electricity
2 General Classes
Dynamic and Static
flow in an electric circuit
ELECTRIC CURRENT
- Flows in one direction (- to +)
- Uniform in strength
- Battery/dry cell
2 types: continuous/pulsating (fluctuating)
DIRECT CURRENT (DC)
- Reverses direction of flow at regular intervals
- Reverses in direction
- Frequency: 60 cps (60 Hertz)
- Phase: SP/3P
- 230VAC, 60Hz, SP
ALTERNATING CURRENT (AC)
- Fixed polarity
- Steady (continuous)
- Varying in magnitude (fluctuating)
- Steady value
- Easier to MEASURE
- 1.5 VOLTS
DIRECT CURRENT (DC)
- Reverse Polarity
- Varies between reversal
- Stepped up or down
- Easier to AMPLIFY
- 110 VOLTS
ALTERNATING CURRENT (AC)
Path for electric current w/ EMF applied
ELECTRIC CIRCUIT
Force which causes movement of electricity in a conductor
Electromotive Force (EMF)
Electrical layout
Circuit Diagram
Broken, incomplete, disconnected
Open Circuit
Complete; Continuous path
Close Circuit
Bridging
Short Circuit
Circuit branching
Shunt
Relationship of EMF, Current, Resistance
OHM’s LAW
Current (Amperes)
I
EMF (Volts)
V
Resistance (Ohms)
R
EMF; pressure or force; Voltmeter
Voltage (Volts)
Inherent in wires (conductor); Ammeter
Amperes (Amps)
Current-carrying capacity (w/o undue heating)
Ampacity
Friction; inherent in insulator/Ohmmeter
Ohms
Does not consume electricity
DEVICE
Rate of power; power consumption;
WATT
Any one time
Watt Meter
periodic; KWH Meter/
Watt-Hour Meter
AC generator
ALTERNATOR
M.E to E.E.
GENERATOR
E.E. to M.E.
MOTOR
Electrochemical; electrolysis
BATTERY
Nonrenewable
Primary
Lines that run along highways and major roads
1500+ customers restored
Ciscuit
The source of electricity
Generating station
Rechargeable
Secondary
High voltage power lines that run cross country
25000+ customers restored
Transmission lines
Distribute power to several circuits
Up to 6000 customers restored
Substation
These serve smaller groups of customers and neighborhoods from the main circuits
50+ customers restored
Tap Lines
Reduces power to usable voltage levels
1-8 customers restored
Individual Transformers
Power supplied to a building through a service entrance. Three
heavy wires (drop), extend from utility poleoverhead wires are
fastened to the structure and spliced to service entrance wires that enter a conduit through a service head; rigid conduit must
be used
SERVICE ENTRANCE (SE - AERIAL)
Three wires are placed in a rigid conduit. An underground
service conduit is brought to the meter socket. An USE includes
a watt- hour meter, main breaker, and lightning protection.
UNDERGROUND SERVICE ENTRANCE (USE)
Offers low resistance
Conductors
Prevents flow of electric current
Insulators
Channel
Raceways
Delivered through adistribution panel,or service panel.
SERVICE DISTRIBUTION
READ
SYSTEM COMPONENTS OF BUILDING
Category 1. WIRINGS AND RACEWAYS
Conductors – offers low resistance
Insulators – prevents flow of electric current
Raceways - channel
Category 2. POWER HANDLING EQUIPMENTS
Transformer, Switchboard/Switchgear, Panel board, Service
Switch/Safety Switch, Circuit Breaker/Fuse
SERVICE DISTRIBUTION – delivered through adistribution panel,or service panel.
Category 3. UTILIZATION EQUIPMENTS – actual use
Fixtures, Switches, Convenience Outlets, Branch Circuits
From the distribution panel, electricity is routed to the building
throughbranch circuits. Each circuit delivers electricity to a
limited number of outlets or devices and protected with acircuit
breaker.
BRANCH CIRCUITS
Branch circuits are divided into three types by the PEC:
lighting circuits
small-appliance circuits
individual circuits
underfloor raceway
- conventional installation
cellular metal floor raceway – rib decking/raised floor system
cellular concrete floor raceways – T-joist/ precast concrete slab with built in pipes
Floor Raceway
- Power and Control Tray
- Cable (TC)
- Busbar
- Cable bus
Ceiling Raceway
H-frame – 1000 kva
Cluster mounted – 225 kva
Pad mounted – 120V to 240V
Outdoor Transformers
voltage to voltage
TRANSFORMER
READ
Dry Type – pad mounted; switchboard
Askarel – synthetic non-flammable liquid
Oil-insulated – for transformer vault
Transformer Rating: stepped up/stepped down