Farm Electrification Flashcards
Electrons found in the outermost shell or orbit of an atom
Valence electrons
Classification of materials according to conductivity
Conductor - 3 or less valence electrons
Semi-conductor- Has exactly 4 valence electrons
Insulator - 5 or more valence electrons
Unit of potential difference which is equal to one joule of work done per one coulomb of charge
Volt
Unit of charge flow equal to one coulomb of charge pass a point in one second
Ampere
Ampere formula
I=Q/t
I- current
Q- number of charges past
t- time(seconds(
Specific heat capacity of water
4, 186 J/kg-°C
Energy required to heatt the water formula
Q= m×c×change in temperature
m= mass of water
c= specific heat capacity of water (4, 186 J/kg-°C
The property of a substance or material which opposes the flow of electrons or current
Resistance
Is the measure of materials ability to conduct electric current
Conductance or electrical conductivity
Unit of conductance
Siemens
G= 1/R
Area of Circular Mil formula
A= d²
A= Ara (CM)
D= diameter (mills)
1 inch= 1000 mils
1 MCM= 1000 CM
Reciprocal of impedance
Admittance
Unit - Siemens
The joint effect of combining resistance and reactants in an ac circuit
Impedance
The voltage and the circuit are in phase
Unity power factor
Lagging pf – the current lags the voltage by an acute angle θ.
Leading pf – the current leads the voltage by an acute angle θ.
Ratio of the true power to the apparent power and also defined as ratio of the resistance to the impedance
Power factor (Pf)
A circuit phenomenon wherein the inductive reactance and capacitive reactants are equal
Resonance
Outer covering of the DC generator wherein the poles are bolted and it is made from cast iron or cast steel
Yoke or Frame
Machine that drives the generator
Prime mover
Is a device that transfers electrical energy from one electric circuit to another without a change in frequency
Transformer
- Only voltage changes
A winding that forms a loop as it expands around the armature core and is suitable for high current dc generator
Lap winding
Used to connect the external load to the armature and made of carbon or graphite and are held in position by spring pressure
Brushes
Consists of hard drawn copper conductors insulated from each other and also called mechanical rectifier
Commutator
A type of DC generator wherein it’s field winding is excited from its own generated in the armature
Self-excited generator
Number of parallel paths in different types of windings
Lap winding - a = Pm
Wave winding - a = 2m
Frog leg winding - a = 2pm
Where: a- no of parallel paths
P- no of poles( even numbers)
m- multiplicity factor
simplex- 1, duplex - 2, triplex- 3
and quadroplex- 4
Acombination of both lap and wave windings
Frog-leg windings
A winding that forms a wave as it expands around the armature core and suitable for high voltage dc generators
Wave winding
Percent rise in the voltage at the terminal of a generator when the load is removed
Voltage regulation
A type of DC generator wherein its field winding is excited from a separate external source such as battery or another generator
Separately excited generators
Opened wire of low melting point commonly used in the safety of powers switch
Fuse wire or fuse
Is enclosed in porcelain or rubber commonly used in various electrical appliances
Plug fuse
Fuse that is enclosed and insulating tube
Cartridge fuse
An over current protective device with a circuit opening fusible element which opens or breaks when there is an over current in the circuit
Fuse
Any current in excess of the rated capacity of the equipment or rated ampacity of the conductor
Over current
Uses dry and compressed air to extinguish the arc
Air-blast CIRCUIT BREAKER
Circuit breakers used when interruption occurs in free air
Air circuit breaker
High voltage fuse specially suited for protecting transformers, capacitor banks, and cables in outdoor distribution substations
Power fuse
Is a combination of a fuse and a switch used in a primary overhead feeder lines and tap to protect distribution transformers from current surges and overloads
Fuse cutout
Used to control (switch on or off) the current path in the circuit
Switch
Converts chemical energy to electrical energy using the chemical materials within the cell to start the action
Primary cell
It is the combination of cell
Battery
A single unit of electrolysis
Cell
A mechanical switching device used to isolate a circuit or an equipment from the supply side
Disconnect
A special type of switch used in conjunction with three ways switches to control a lamp from three or more different location
Four-way switch
Type of circuit wiring design for interior use in dry location
NM ( non-metalic) cable
The modern normally rotates at the same speed as the revolving field in the machine
Synchronous motor
Design to provide high starting torque for loads with high inertia while requiring very low current
Wound rotor
A cylindrical shaped cage that fits the shaft with bars extending between its two ends
Squirrel cage
Must be charged with electrical energy before it can convert chemical energy to electrical energy
Secondary cell
Single conductors each with its color coded insulation usually used as conduit in houses
THHN and THWN
A type of non metallic cable design for wet locations and direct burial in the ground
Underground Feeder cable
Is a is a strong durable thick walled steel tubing made using a hot dip galvanization process to help avoid corrosion
Rigid metal conduit or galvanized rigid conduit
Type of wiring that features a metal jacket around the wires to protect them from damage
Armored cable
Holds up well in areas where salty air is a problem including coastal regions
Aluminum conduit
Is easy to install flexible cost efficient and lighter than other types of conduits
Electrical metal conduit
Sizing of power fuses
For non time delay fuse- size= 300% of Full Load Amperage (FLA)
For time delay fuse- Size = 175% of FLA
Sizing power circuit conductors
Size= 125% of FLA (full load amperage)
Sizing Disconnect switch
Size= 125% of FLA
Is a thin walled highly flexible pvc conduit that can be bent by hand
Electrical Non-metalic Tubing (ENT)
Feeder circuit conducts size
Conductor size= 125% FLA of largest motor + sum of FLA of remaining motors
Sizing of branch circuit conductors
125% FLA
Thermal relay/overload relay setting
Setting= 125% of FLA if the service factor SF= 1.15
Setting= 115% of FLA if service factor SF= 1.0 or not written
Used for switching the motor load
Magnetic contractor
Sizing of circuit breaker
Size= 700% FLA (instantaneous trip circuit breaker)
Size= 250% FLA (inverse time circuit breaker)
A combination of the arc discharge characteristics of the fluorescent lamp and the shape of an incandescent lamp
Mercury lamp
- requires ballast and a certain warm-up period before discharging
The most energy efficient lamp up to 200 lumens per watt
LED Lamp
One of the most commonly used lamp which consumes lesser energy that an incandescent lamp
Fluorescent lamp
- pleasant light
-noisy due to ballast hum
The least efficient lamp around 14 lumens per watt
Incandescent lamp
Sizing power of feeder protective device
Size= largest motor protective device+sum of FLA of the remaining motors
Illumination equation
E = F/A
where:
E- illumination
F- Luminous flux (Lumen)
A- Area, m²
The intensity of light per unit area
Illumination
Special type of incandescent lamp known as quartz lamp
Tungsten Halogen Lamp
Luminous effeciency equation
LE= F/P
Where:
F- Luminous flux (Lumen)
P- Power input of light source (watt)
Amount of luminous flux it radiates per what of power input
Lumens effeciency
Luminous intensity equation
I= F/w
Where:
F- Luminous flux (lumen)
w- solid angle (steradian)
= 4π(solid angle)
Illumination on surface formula
E= Icos(angle)/r²
Where:
I- luminous intensity (candela)
r- distance of the light source to point p (m)
angle- angle of incidence
Zonal cavity or average illumination method formula
Eave= F×N×Cu×Df/A
Where:
F- Lumens output per lamp (lumens)
N- Number of lamps
Cu- coefficient of utilization
Df- depreciation factor
A- surface area illuminated, m²
Solid angle equation
w= A/R²
Where:
A- surface area, m²
R- distance from the point of observation (m)
Three dimensional equivalent of a face angle expressed in steradians
Solid angle
The unit of magnetic flux in SI is
Weber
A small lamp used to indicate that a circuit
is energized.
Pilot lamp
An instrument that measures the voltage
or electrical pressure in a circuit
Voltmeter
A good capacitor has a ____ resistance.
very high
