Download Basic Electrical Principles

EKAS 2.8.1.1
Basic Electrical Principles
UEE31307 Certificate III in
Refrigeration and Air Conditioning
Stage 2A
Units: UEENEEPOO1B, UEENEEPOO2B
Chris Hungerford
Sunday, May 7, 2017
Hazards & Unsafe work practices
• Electric Shock
• Arcing
• Smoke
2..8.1.1A
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Unauthorized electrical work.
Inadequate work practices.
Live work.
Disregarding earthing circuits.
Untested test equipment.
Lack of tool maintenance.
Laziness & fatigue.
Workplace fool.
Untested work before commencing work.
Untested work connected to a supply.
Disregard to Australian Standards.
Safety practices in the use of common tools and plant
Employees who are exposed to the hazards of falling, flying, abrasive
and splashing objects, or exposed to harmful dusts, fumes, mists,
vapors, or gases must be provided with personal protection
equipment (PPE) necessary to protect them from the hazard.
All hazards involved in the use of tools and plant can be prevented by
following five basic safety rules:
1.
2.
3.
4.
5.
2..8.1.1A
Keep all tools and equipment in good condition with regular maintenance.
Use the right tool for the job.
Examine each tool and plant for damage before use.
Operate according to the manufacturer's instructions.
Provide and use the proper protective equipment.
Low voltage rescue
Accident
Rescuer’s safety
No
Rescue kit, Gloves & crook
Correct PPE
Yes
Isolate Supply
Free victim
Yes
Fire
Use fire
blanket
Unsafe
area
Use drag
method
No
No
Yes
Clear area
Assess victim’s condition
Resuscitate, treat burns & injuries
Await medical assistance
2..8.1.1.B
Send for help
as soon as the
situation allows
Burns
Management
WARNING
• Do not apply lotions,
ointment or fat to burn.
• Do not touch the injured
area or burst any
blisters.
• Do not remove any thing
sticking to the burn.
• Keep a check for shock.
2..8.1.1.B
• Remove casualty from
danger, DRABC.
• Cool the burnt area, hold
under cold running water for
10 min.
• Remove any constrictions,
unless sticking to the burn.
• Cover burn.
• Calm casualty
• Call 000 for an ambulance.
Bleeding
WARNING
Management
• Apply pressure to the
• Wear gloves to guard
wound.
against infection.
• Raise and support injured
• If casulalty becomes
part.
unconscious - DRABC.
• Do not apply a tourniquet. • Bandage wound.
• Check circulation below
wound.
• Treat for shock.
• Call 000 for an ambulance.
2..8.1.1.B
Shock
Signs & symptons
• weak, rapid pulse
• cold, clammy skin
• rapid breathing
• faintness/dizziness
• nausea
• pale face, fingernails,
lips
2..8.1.1.B
Management
• Lie casualty down, protect them
from cold ground.
• Calm the casualty.
• Follow DRABC.
• Manage any injuries.
• Ensure comfort, if thirsty,
moisten lips.
• Monitor breathing and pulse.
• Place in recovery position.
• Call 000 for an ambulance.
DRABCD
D
R
A
B
C
2..8.1.1.B
D
danger
response
airway
breathing
circulation
defibrillator
Danger
• to you
• to others
• to the casualty
Make sure you don’t
become a second casualty
2..8.1.1.B
Response
- is the casualty conscious?
• gently shake the casualty and ask “Can you
hear me?”, “What is your name?”
• if the casualty is conscious, check for and
manage bleeding and other injuries.
• if the casualty is unconscious, they should
be turned on the side
2..8.1.1.B
Airway Australian Resuscitation Council http://www.resus.org.au/ Guideline 4.
Clear airway: If foreign material is present in mouth,
roll casualty on side and clear mouth with their fingers.
Tilt head backward. Place one hand on the
forehead and use the other hand to lift the chin.
2..8.1.1.B
Breathing
Look for the chest rising and falling
Listen for the sound of breathing
Breathing
Yes - place casualty in side position
No – seal nose and give 2 breaths into mouth.
2..8.1.1.B
Circulation
feel the pulse at the neck (carotid pulse)
No- commence CPR (cardiopulmonary
resuscitation), 2 breaths & 30 compressions at a
rate of approximately 100/ minute.
5 cycles in 2 minutes
Compress 1/3 depth of chest.
Rescuers should minimize interruptions of chest
CPR to check for signs of life.
2..8.1.1.B
Defibrillator
• Minimise interruptions to chest
compressions
• Give a single Defibrillator shock for
ventricular fibrillation.
• If arrest is witnesses by a health care
professional and a manual defibrillator is
available, 3 shock may be given.
• After each defibrillation attempt give 2
minutes of CPR.
2..8.1.1.B
The FIRE triangle
Three components are required for a
fire to exist: fuel, heat, and oxygen
Removing any one of these
components the fire will not exist.
To reduce the chance of fire in the
workplace all three need to be kept
separate.
Heat
Oxygen
Fuel
2..8.1.1.C
2..8.1.1.C
PCB’s
Polychlorinated biphenyl
PCB,s congeners are odourless, tasteless, clear to pale-yellow, viscous liquids. They are
formed by electrophilic chlorination of biphenyl with chlorine gas.
They have high dielectric constants, very high thermal conductivity, high flash points
(from 170 to 380 °C) and are chemically fairly inert, being extremely resistant to
oxidation, reduction, addition, elimination, and electrophilic substitution.
PCBs readily penetrate skin, PVC (polyvinyl chloride), and latex (natural rubber).
PCBs are very stable compounds and do not degrade readily. Their destruction by
chemical, thermal, and biochemical processes is extremely difficult, and presents the
risk of generating extremely toxic dibenzodioxins and dibenzofurans through partial
oxidation.
PCBs were used as coolants and insulating fluids ('transformer oil') for transformers and
capacitors especially in components of early fluorescent light fittings, electrical
transformers, plasticizers in paints and cements, stabilizing additives in flexible PVC
coatings of electrical wiring and electronic components, pesticide extenders, cutting
oils, reactive flame retardants, lubricating oils, hydraulic fluids, sealants, adhesives,
wood floor finishes, water-proofing compounds, casting agents, vacuum pump fluids,
fixatives in microscopy, surgical implants, and in carbonless copy ("NCR") paper.
Studies of workers indicate that PCBs were associated with specific kinds of cancer in
humans, such as cancer of the liver and biliary tract. Polychlorinated biphenyls
(PCBs) have been shown to mimic the action of oestrogen in breast cancer cells and
can enhance breast carcinogenesis.
PCB waste must be treated by a licensed/approved operator. Solid and liquid scheduled
waste must not go to landfill. Quantities above 10kg must be notified to Department
of Environment and Heritage.
2..8.1.1.C
Simple Electric Circuit
• The basic electric
circuit consists of
the following
three
components.
1. a source
2. a complete path
3. a load to do work
2.8.1.1 D
The Source
• a source of electrical
pressure :- battery to
provide electrical energy for
the system.
• other types of sources:
generators, alternators,
solar cells, piezo crystals.
2.8.1.1 D
The Source
The source is known as an EMF device.
Electron Motive Force.
It places the electron in motion by creating a
pressure difference, therefore the unit of an
EMF is volts.
2.8.1.1 D
Types of sources
Electro-magnetic - alternators, generators.
Photo-electric ----- solar cells.
Thermo-electric --- thermocouples
Piezo-electric ------ gas lighters, microphones
Chemical ---------- cells and batteries
Static ---------------- lightning.
2.8.1.1 D
Component identification
Resistive components:-
all
devices that have a principle function
of producing heat.
Inductive components:-
any
device that has a coil and principle
operation uses magnetism.
Capacitive components:-
any
device that stores an electro-static
charge.
2.8.1.1 D
Resistance
Resistance is the opposition
to the flow of electrons.
All materials exhibit a value
of resistance to the flow
of electrons. A good
conductor has a small
resistance, while an
insulator has very high
resistance.
Resistance is a lot
like friction; they
both act to oppose
motion and
generate heat.
2.8.1.1 D
Component function
Impedance
AC resistance
Reactance
Resistance
Urns
Heaters
Irons
Inductance
Toasters
Motors
Transformers
2.8.1.1 D
Capacitance
Relays
Capacitors
Open Circuit
An open circuit prevents current flow.
A switch, fuse, or circuit breaker
when operated will produce an open
circuit.
An open switch
Open switch
lamp is off.
2.8.1.1 E
Closed Circuit
A closed circuit allows current to
flow. A switch can control both
open and closed circuits.
Closed switch
2.8.1.1 E
Closed switch
lamp is on
Short Circuit
This type of circuit is to be avoided whenever
possible. The lamp is bypasses by a conductor
connected directly across the supply and
reducing the circuit resistance.
High current flow
Little current flow through the
lamp, however excessive current
flows in the short.
Little current
The pressure of the circuit (volts)
will also drop.
Short circuit
2.8.1.1 E
Ohms Law
The current flowing in a circuit
is proportional to the voltage
and inversely proportional to
the resistance of the circuit.
V = Voltage
I = Current
R = Resistance
2.8.1.1 E
V
I
R
Proportional to
Proportional to , values that are
directly opposite to each other in a
formula is proportional to each other.
Hexagon is proportional
to the square.
=
Star is proportional to
the circle.
2.8.1.1 E
Inversely proportional to
Inversely proportional to, values that are
diagonal to each other are inversely
proportional to each other.
This technique applies to all formularies.
The star is inversely
proportional to the square.
=
The hexagon is inversely
proportional to the circle.
2.8.1.1 E
Triangle & thumb
To transpose the formula,
draw the triangle as
shown.
Voltage = ?
Move thumb over voltage
and the remainder
equals the voltage.
2.8.1.1 E
V
I
R
Triangle & thumb
Voltage = current X resistance
Determine the resistance.
V
I
2.8.1.1 E
R
Triangle & thumb
Thumb over the resistance.
Resistance = the remainder.
Resistance = voltage/current
V
I
2.8.1.1 E
R
Transposing formula
Current = voltage / resistance
Resistance = voltage / current
Voltage = current X resistance
2.8.1.1 E
I=V
R
R=V
I
V=I R
Applying Ohms Law
Determine the current flow.
I=?
10v
V
I
2.8.1.1 F
5
R
I = V = 10
R
5
= 2A
Applying Ohms Law
Determine the Resistance.
I=5A
V
I
100v
R
R = V = 100
I
5
2.8.1.1 F
R=?
= 20
Applying Ohms Law
Determine the Voltage.
I=12A
V
I
V=?
20
R
V=I R = 12 x 20 = 240v
2.8.1.1 F
Problem Solving
Voltage Current Resistance
I
50v 5A
V
R
16
240v
1A 12
Calculate the missing value
using ohms law.
2.8.1.1 F
Summary
Ohms law is the relationship
between voltage, current,
and resistance.
50v 5A 10
240v 15A 16
12v 1A 12
2.8.1.1 F
Problems
Determine the resistance of a 240v heating
element that has a current of 20amps.
A 240v light bulb, has a measured
resistance of 960, determine the circuit
current.
2.8.1.1 F
A 240v element of 48 has been replaced
by a 240v element with a resistance of
16. If the circuit is protected by an 8A
circuit breaker, determine the effects on
the circuit.
AS/NZS-3000:2007, Wiring Rules
3.7 ELECTRICAL CONNECTIONS
3.7.1 General
Connections between conductors and between
conductors and other electrical equipment shall
provide electrical continuity and adequate
mechanical strength.
2..8.1.1.G
Solderless lugs
Ross - Courtney lug.
Stanco lug
2..8.1.1.G
Crimps
Terminating - crimp lugs.
Joining cables of the same size - crimp links.
When crimping it is important that the correct crimp
type lug for the cable and the correct tool for that
lug is used.
AS/NSZ 3000 cl 3.7.2.3.2
2..8.1.1.G
Terminal connections
AS/NZS 3000 cl 3.7.2.4
Blue point connectors (BP)
Line taps.
Articles terminals.
Terminal strips.
Bolted & clamp
connectors,
2..8.1.1.G
AS/NZS-3000:2007 Wiring Rules
3.7.2.7 Soldered connections
Where a soldered connection is used
the design shall take account of
creep, mechanical stress and
temperature rise under fault
conditions.
2..8.1.1.G
Stripping of Insulation.
•
•
•
•
•
•
2..8.1.1.G
Avoid using a knife on smaller cables.
Tear the insulation off, don’t cut.
Do not indent any conductor material.
Be sure not to remove excessive insulation.
Remake any damaged insulation.
The only connection for an extension lead is via
an approved plugtop and socket.
AS/NZS-3000:2007 Wiring Rules
3.7.2.2 Preparation for connection
The insulation on a conductor shall not be
removed any further than is necessary to make
the connection.
For connections between insulated conductors the
connection shall be insulated to provide a degree
of insulation not inferior to that of the conductors.
Any damaged insulation shall be reinstated.
2..8.1.1.G
Terminations and connections
• Connections must not be soft soldered
before compression terminations.
• Must be seated correctly.
• Free of dirt and oxides.
• Use a suitable lug or connector.
• Insulated to the equivalent of the original
insulation.
• Earth connection must be painted if
exposed to weather
2..8.1.1.G
AS/NZS-3000:2007 Wiring Rules
3.7.2.6 Mechanical stress
All cables and conductors shall be installed
so that there is no undue mechanical
stress on any connection.
2..8.1.1.G
AS/NZS-3000:2007 Wiring Rules
3.7.2.3.1 Loosening of connections
Connections shall be made so that no
loosening is likely because of vibration,
alteration of materials or temperature
variations to which the connections
are likely to be subjected in normal service.
2..8.1.1.G
Further reading: Workbook Risk management
Questions: Workbook, Topic 3, Q1 – Q90