Electrical Apparatus & Circuits Flashcards
Low Voltage (LV)
Between 50V & 1000V AC or 120V to 1500V DC (License Required)
High Voltage (HV)
More than 1000V AC or 1500V DC (License Required)
Extra Low Voltage (ELV)
Below 50V AC or 120V DC (No License Required)
MEN
Multiple Earthed Neutral
Three-Phase Colour Coding (New)
L1 (Brown, L2 (White), L3 (Grey), N (Blue), E (Green/Yellow). The phases are 120 Deg. apart
Three-Phase Colour Coding (New, Equipment)
L1 (Brown, L2 (White), L3 (Grey), N (Blue), E (Green/Yellow). The phases are 120 Deg. apart
Three-Phase Colour Coding (Old)
L1 (Red), L2 (White), L3 (Blue), N (Black), E (Green)
Leading Edge
In a Square or Sawtooth Wave; the ascending edge of the wave.
Trailing Edge
In a Square or Sawtooth Wave; the descending edge of the wave.
Three-Phase Colour Coding (New, Installation)
L1 (Red), L2 (White), L3 (Blue), N (Black), E (Green/Yellow)
Three-Phase Colour Coding (New, Installation)
L1 (Red), L2 (White), L3 (Blue), N (Black), E (Green/Yellow)
PEN
Protective Earth Neutral
Star Point
The terminals of the three branches are connected to a common point. The network formed is known as Star Connection
Delta Point
The three branches of the network are connected in such a way that it forms a closed loop known as Delta Connection
EPR
Earth Potential Rise
In a sine wave, RMS Voltage equals…
…Peak Voltage x Square Root of 2
Step Potential
An electrified grounded object radiates electricity in rings. Stepping across these rings can cause current to flow through your body.
In a sine wave, RMS Voltage equals…
…Peak Voltage x Square Root of 2
Australian Wiring Standard
Wiring Rules AU/NZS 3000
Touch Potential
Touching an electrified object has the potential to allow electricity to flow through your body to the ground.
RCD, RCCB, ELCB
Residual Current Device / Residual-Current Circuit Breaker / Earth-leakage Circuit Breaker. Can be single or three phase.
Toroidal Coil
…
MCB
Miniature Circuit Breaker
Tong Tester / Clamp Meter
…
Type 1 RCD
10mA - Medical
Type 2 RCD
30mA - Domestic
Type 3 RCD
100mA
Type 4 RCD
100mA
GPO
General Power Outlet
Earth Pit
…
Earth Stud / Bar
…
Primary and Secondary Transformer
…
Earth Potential Rise (EPR)
…
Equipotential
(of a surface or line) Composed of points all at the same potential.
Installation Categories
Category I: Electronic circuits
Category II: Portable appliances
Category III: All distribution circuits, mains, air-conditioners, hot water heaters, ranges
Category IV: Consumer mains, power consumption meters,
Ingress Protection (IP)
…
HRC Fuse
High Rupturing Capacity Fuse
gG (gL), gM Fuses
…
Motors are rated in two units:
Horsepower (HP) or Kilowatt (kW)
NEMA, IEC
National Electrical Manufacturers Association, International Electrotechnical Commission
Burden of Coil
…
Inverse Time Graph
…
Hysteresis
The phenomenon in which the value of a physical property lags behind changes in the effect causing it, as for instance when magnetic induction lags behind the magnetizing force.
Hysteresis
The phenomenon in which the value of a physical property lags behind changes in the effect causing it, as for instance when magnetic induction lags behind the magnetizing force.
NO / NC
Normally Open, Normally Closed
Enamel
An opaque or semi-transparent glossy substance that is a type of glass, applied by vitrification to metallic or other hard surfaces for ornament or as a protective coating.
PCB
Printed Circuit Boards
Interlocking, Cross-Interlocking
…
Cowl
A protective covering for a circuit or apparatus.
Contactor
A contactor is an electrically-controlled switch used for switching an electrical power circuit.
CE (manufacturing symbol)
The CE mark indicates that the product may be sold freely in any part the European Economic Area, irrespective of its country of origin.
SPDT
Single Pole Double Throw, a switch that only has a single input and can connect to and switch between 2 outputs.
Switchgear
…
Gland
A sort-of sleeve, either metal or PVC, which holds the insulation of a cable and keeps it steady within a device.
Gland Plate
The plate on which a gland is attached
Lug
A type of connector - the cable is crimped into the open end of the lug, the other end is designed to be bolted
Neutral and Earth Bars
…
Earth Stake or Rod
…
Looping
The continuation of a control circuit by looping from one input to the next. It’s bad practice to put more than two cables per terminal.
Wire Guage
The measurement of a wire’s diameter, determining the amount of current the wire may carry.
Make-Before-Break
A control switch which closes one contact before opening another
Break-Before-Make
A control switch which opens one contact before opening another
Jogging and Inching
The quickly repeated closure of a circuit to start a motor from rest for the purpose of accomplishing small movements of the driven machine. The term inching means to start a motor with short jabs of power at reduced volt age. Although the two terms mean different things, they are often used interchangeably
DOL Starter
Direct On Line starter or across the line starter
EI Transformer
The traditional form of transformer, as opposed to a Toroidal Transformer
FLA
Full Load Amps
FTL
Fluorescent Tube Light
Simmerstat
Also known as an energy regulator or infinite switch - Simmerstats are responsible for turning the heating elements on and off in hobs, grills, and various other cooking appliances.
Entropy
…
Ethalpy
…
Absolute Zero
-273.15 deg. Celsius, or 0 deg. Kelvin
Three Modes of Heat Transfer:
Conduction, Convection, Radiation.
Dew Point
The dew point is the temperature to which air must be cooled to become saturated with water vapor. When cooled further, the airborne water vapor will condense to form liquid water. When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface.
Instantaneous (Tankless) Water Heater
…
Black Body
A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name “black body” is given because it absorbs radiation in all frequencies, not because it only absorbs: a black body can emit black-body radiation
GLS Bulb
General Lighting System Bulb
BC and ES (Light Bulbs)
Bayonet Cap and Edison Screw
VIBGYOR
Rainbow Colours (Violet, Indigo, Blue, Green, Yellow, Orange, Red)
Candela (cd, pl. candelas), Lumen (lm, pl. lumens) and Lux (lx, pl. luxes/luces), Candela/square metre (cd/m^2)
SI units of Luminous Intensity, Luminous Flux and Illuminance, Luminance.
Solid Angle
In geometry, a solid angle is a measure of the amount of the field of view from some particular point that a given object covers. That is, it is a measure of how large the object appears to an observer looking from that point.
Steradian
The SI unit of solid angle, equal to the angle at the centre of a sphere subtended by a part of the surface equal in area to the square of the radius.
Types of Lamps:
Incandescent Globe, Fluorescent Globe, LED, Sodium and Mercury
Sodium Lamp
There are two kinds of sodium lights: Low Pressure (LPS) and High Pressure (HPS). These lamps are mostly used for street lighting (visible through fog) as well as industrial uses. The lamp works by creating an electric arc through vaporized sodium metal. Other materials and gases are used to help start the lamp or control its color.
Mercury-Vapor Lamp
A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb. Used in industrial settings when they can be safely installed.
General Purpose Lighting System
A lighting system for general use, as opposed to when specific lighting is required (such as in photography, textiles, etc.)
Accent Lighting
Accent lighting focuses light on a particular area or object. It is often used to highlight art or other artifacts. Common types of accent lights include wall sconces, floodlights, recessed lights, torchère lamps, or track lighting.
Four Effects of Current Flow:
Magnetic, Physiological, Chemical, Thermal
Cable Temperature Rating:
V#
SAI Global
…
Flywheel
A flywheel is a mechanical device specifically designed to efficiently store rotational energy, which is proportional to the square of its rotational speed and its mass.
Earth Fault
Earth Fault is an inadvertent fault between the live conductor and the earth. When earth fault occurs, the electrical system gets short-circuited and the short-circuited current flows through the system. The fault current returns through the earth or any electrical equipment, which damages the equipment.
Rheostat
A rheostat is a variable resistor which is used to control current. They are able to vary the resistance in a circuit without interruption. The construction is very similar to the construction of a potentiometers. It uses only two connections, even when 3 terminals (as in a potentiometer) are present.
Potentiometer
A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat.
Wirewound Resistor
A wirewound resistor is an electrical passive device that limits or restricts current flow in a circuit.
Bulb and Capillary
Bulb and Capillary style thermostats use expanding liquid to open or close contacts in response to temperature changes.
Minimum Oil Circuit Breaker (MOCB)
The minimum oil circuit breaker will place the interrupting unit in an insulating chamber at the live potential. But insulating material is available in the interrupting chamber. It requires less amount of oil so it is called a minimum oil circuit breaker.
Arc Chute
It is a set of metal plates that are arranged in parallel and mutually insulated from each other, which can divide, cool and safely extinguish an electric arc. They are also known as arc splitters and arc dividers.
OCPD
Open Circuit Protection Device
MCCB
Molded-Case Circuit Breaker
SF6 (Sulfer Hexafluoride)
Sulfur hexafluoride or sulphur hexafluoride, is an inorganic, colorless, odorless, non-flammable, non-toxic but extremely potent greenhouse gas, and an excellent electrical insulator. SF ₆ has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule.
Two main components of an induction motor
Stator and Rotor
Wet and Dry Relays
A “wet” contact could refer to a contact that’s switched with power applied - or to a mercury wetted switch. … A “dry” contact is EITHER: A relay contact that is opened or closed without any voltage present.
Field Excitation
FIELD EXCITATION When a dc voltage is applied to the field windings of a dc generator, current flows through the windings and sets up a steady magnetic field. This is called FIELD EXCITATION. This excitation voltage can be produced by the generator itself or it can be supplied by an outside source, such as a battery.
Under and Over Voltage
Over voltages are the voltages that exceed the normal or rated values which cause insulation damage to electrical appliances leading to short circuits. Similarly, under-voltage causes overloading of the equipment leading to lamp flickers and inefficient performance of the equipment.
VA Rating
VA is a measure of the “apparent power” of an electrical circuit, which is equal to the product of root-mean-square (RMS) voltage and RMS current. It is the value to be used for sizing wires and fuses. For example, a VA rating of 47 using 120V AC would have a current draw of 0.38 amps.
Centrifugal Switch
A centrifugal switch is an electric switch that operates using the centrifugal force created from a rotating shaft, most commonly that of an electric motor or gasoline engine. The switch is designed to activate or de-activate as a function of the rotational speed of the shaft.
Run and Start Capacitors
Run capacitors are designed for continuous duty, and are energized the entire time the motor is running. Single phase electric motors need a capacitor to energize a second phase winding. … Start capacitors increase motor starting torque and allow a motor to be cycled on and off rapidly.
Coasting
The continued movement of a motor by inertia after the power is disconnected
Diac and Triac
…
CRI - Colour Rendering Index
A colour rendering index is a quantitative measure of the ability of a light source to reveal the colours of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in colour-critical applications such as neonatal care and art restoration.
Thyristor
A thyristor is a solid-state semiconductor device with four layers of alternating P- and N-type materials. It acts exclusively as a bistable switch, conducting when the gate receives a current trigger, and continuing to conduct until the voltage across the device is reversed biased, or until the voltage is removed.
Luminous Efficacy
Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt in the International System of Units.
Iccc ≥ ICB ≥ ILoad
The continuous current-carrying capacity of the cable must be greater than the current rating of the protective device, which must itself be greater than the current rating of the load.
Creep (Deformation)
In materials science, creep (sometimes called cold flow) is the tendency of a solid material to move slowly or deform permanently under the influence of persistent mechanical stresses.
Van de Graaff Generator
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate electric charge on a hollow metal globe on the top of an insulated column, creating very high electric potentials. It produces very high voltage direct current electricity at low current levels.
Suspension Socket
An extension cord designed to suspend from the ceiling, featuring a switch for isolation purposes.
Luminaire
Luminaire refers not just to the lamp, but rather the entire lighting unit.
Halogen Lamp
A halogen lamp, also known as a tungsten halogen, quartz-halogen or quartz iodine lamp, is an incandescent lamp consisting of a tungsten filament sealed into a compact transparent envelope that is filled with a mixture of an inert gas and a small amount of a halogen such as iodine or bromine.
Halide
A halide is a binary phase, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a, e.g., fluoride, chloride, or theoretically tennesside compound.
Stroboscopic Effect
The stroboscopic effect is a visual phenomenon caused by aliasing that occurs when continuous motion is represented by a series of short or instantaneous samples.
f = C/λ (frequency of light formula)
Where, λ (Lambda) = Wavelength in meters. c = Speed of Light (299,792,458 m/s)
λ = 380nm to λ = 780nm
Spectrum of visible light
Glare
When a bright light source is contrasted with a dark background; causing visual discomfort
Types of diffusers
Prismatic, Parabolic, Metal or Plastic Louvres
Xenon Lamp (commonly used in modern cars)
Xenon HID (High Intensity Discharge) bulbs are filled with Xenon gas and contain two electrodes - one on each end of the tube-like bulb. When the bulb is switched on, an electric current passes between the two electrodes and the Xenon gas lights up. The Xenon gas is actually only used during the start-up of the bulb.
De Boer Scale
A scale for rating glare discomfort
Emergency Lighting and Exit Signage is covered by:
BCA (Building Code of Australia)
CCT
Color temperature (Correlated Color Temperature, or CCT, in lighting tech jargon) is essentially a gauge of how yellow or blue the color of light emitted from a light bulb appears. It’s measured in the Kelvin unit and is most commonly found between 2200 Kelvin degrees and 6500 Kelvin degrees.
Types of Glass:
Annealed, Heat-Strengthened, Tempered, Laminated
Momentary vs. Maintained
Switches which activate only when pressed, as opposed to switches which retain their position (toggled)
Switch Actuation
The action which causes a switch to change its state. Actuation can occur manually or automatically, electromagnetically (relay), mechanically
PTH & SMT (or SMD)
Through-Hole switch - Surface Mount switch
IEEE
Institute of Electrical and Electronics Engineers
Freewheel or Flyback Diode
A flyback diode is a diode connected across an inductor used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply current is suddenly reduced or interrupted. It is used in circuits in which inductive loads are controlled by switches, and in switching power supplies and inverters.
Maintained, Non-Maintained, Sustained Emergency Lighting
Maintained emergency lights are always on, powered from the mains supply. If the mains drops out, the lights switch to an internal battery. Non-Maintained emergency lights only engage when the mains supply drops out. Sustained is a mixture of the two; a fitting which contains two or more lights where at least one operates in non-maintained.
Three types of Thermostat:
Bimetal, Strut and Tube, Bulb and Capillary
SCR (Silicon Controlled Rectifier)
A silicon controlled rectifier or semiconductor controlled rectifier is a four-layer solid-state current-controlling device. The principle of four-layer p–n–p–n switching was developed by Moll, Tanenbaum, Goldey and Holonyak of Bell Laboratories in 1956.
VESDA System
VESDA Systems are aspirating smoke detection used for early warning applications where response to a fire is critical. VESDA® works by continually drawing air into the pipe network via a high efficiency aspirator. A sample of this air is then passed through a dual stage filter.
Iron Loss
The losses which practically occur in an unloaded transformer are the iron losses, which are the sum of the hysteresis and eddy current losses. It is the power dissipated in the magnetic core subjected to a time varying magnetizing force.
Core type, Shell type Transformers
In the “closed-core” type (core form) transformer, the primary and secondary windings are wound outside and surround the core ring. In the “shell type” (shell form) transformer, the primary and secondary windings pass inside the steel magnetic circuit (core) which forms a shell around the windings as shown below.
Concentric, Sandwich or Pancake, Side by Side Transformers
This refers to the different arrangements of the coil when there is a secondary winding on the transformer
Galvanic Corrosion, Local Electrolytic Effect
Galvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte.
Air-filtering liquids used in large transformers
Silica Gel, Copper Sulphate
Current and Potential/Voltage Transformer
There are several types of differences between the voltage and the current transformer. One of the major difference between them is that the current transformer converts the high value of current into low value whereas the potential or voltage transformer converts the high value of voltages into low voltage.
Variable Transformer
Variable transformers are transformers that can put out differing amounts of voltage from the same input voltage. … Variable transformers are a type of autotransformer, which is a transformer that does not have the dual-coil core design.
Types of MCB
Type A, B, C, D, K and Z.
Type B devices are designed to trip at fault currents of 3-5 times rated current (In). For example a 10A device will trip at 30-50A.
Type C devices are designed to trip at 5-10 times In (50-100A for a 10A device).
Type D devices are designed to trip at 10-20 times In (100-200A for a 10A device).
Two Types of Smoke Detectors
There are two main kinds of smoke detectors – ionisation and photoelectric. Ionisation alarms are good at detecting flaming fires, whereas photoelectric are more effective at detecting smouldering fires (slow-burning, smokey fires).
Ionisation smoke detectors use an open-air ionisation chamber and a few micrograms of americium 241, which is a radioactive material. As the radioactive matereial decays, it produces a stream of alpha particles. These particles ionise nitrogen and oxygen atoms in the air in the ionisation chamber.
Intrinsic Safety
Intrinsic safety is dependent on a circuit operating at little power and acceptable temperatures so that it does not have the required energy to ignite a flammable atmosphere.
