Transcript Basic Electrical Concepts and Hazards Circuit

NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II:
Basic Electrical
Concepts
And Hazards
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Module II Objectives
Terminal Objective
Describe basic electrical concepts that pertain
to P/HEVs and EVs.
Enabling Objectives
● Define basic electrical terms.
● Understand the difference between
electrical systems found in structures and
those found in P/HEVs and EVs.
● Understand how electricity affects the body
and how to protect against electric shock.
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Module II Outline
● Electrical terms
● Types of electricity
● Understanding electrical circuits
● Building electrical systems vs. vehicle
electrical systems
● Effects of electricity on the body
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Basic Electrical Terms
Voltage:
Electrical Potential
• Comparable to
water pressure or
PSI in a hose.
• Measured in Volts.
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Basic Electrical Terms
Current:
Quantity of electrons flowing
• Comparable to
the rate of flow of
water or gallons
per minute (GPM).
• Measured in
Amperes.
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Basic Electrical Terms
Resistance:
A material’s opposition
to conducting current
• Comparable to
friction loss in hose
lines or appliances.
• Measured in Ohms.
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DC Circuits
Typically found in
electronic devices that
utilize battery power
and some industrial
applications.
AC Circuits
Found anywhere electricity is
supplied by the utility
company from the power
grid, such as in buildings.
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DIRECT CURRENT VS. ALTERNATING CURRENT
Direct
Current
Current always flows
in the same direction.
Alternating
Current
Current repeatedly
reverses direction.
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Types of Electricity Found
in P/HEVs and EVs
DC
AC
● Found in all P/HEVs
and EVs.
● Found in some
P/HEVs and EVs.
● All use batteries
for electrical storage.
● These models use AC
motors.
● DC is converted to AC.
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Understanding Electrical
Circuits
● With both AC and DC, there must
be a completed path, or circuit, for
current to flow.
ON
OFF
● A switch creates a break in the
circuit when “OFF”.
● Turning the switch “ON” completes
the circuit, allowing current to flow.
● Injury can occur when a person’s
body becomes part of a circuit by
completing a path for current.
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Video
Electrical
Circuits
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Video
Electrical
Circuits
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Vehicle vs. Building
Electrical Circuits
● All HV circuits (AC or DC) are isolated from
the vehicle chassis.
● Safeties will cause a
vehicle HV system to
shut down should
chassis become
part of the circuit.
HV
POWER
SOURCE
ELECTRIC
MOTOR
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Vehicle vs. Building Electrical Circuits
● To receive a shock, you must place your body in a
position to become part of a circuit.
● Unlike in a structure,
the earth is not part of
the circuit design.
● Introducing a path to
ground (touching or
spraying water) will
not, by itself,
complete a circuit.
HV
POWER
SOURCE
ELECTRIC
MOTOR
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How Electricity Affects the Body
● Human body and PPE provide some
resistance to electricity.
● Voltage must be high
enough to overcome
resistance before it
can enter your body.
● Environmental
conditions, like
being wet, can
greatly reduce
resistance.
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How Electricity Affects the Body
● Once resistance is
overcome, Amperage
usually determines
degree of damage.
● Circuits in P/HEVs and
EVs have both the
voltage and amperage
to be considered
highly dangerous.
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How Electricity Affects the Body
Examples
● 9V battery: Not enough
voltage to overcome
resistance of dry skin
● Stun Gun: High
voltage, but not
enough amps to do
real damage.
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How Electricity Affects the Body
Analogy
● A 2 PSI low pressure hose
flowing at 3 GPM would
not hurt if aimed at you.
● A 1000 PSI pressure
washer, pushing the same
3 GPM could seriously
harm you.
● The high pressure
(voltage) allows the
current to overcome your
skin’s resistance.
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DC Current Effect on Humans
Milliamps (1000 mA = 1 A)
240
70
40
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OBSERVABLE EFFECT 2
Possible Ventricular Fibrillation
Electrical Burns
Can’t let go
Startle Reaction
Some models of P/HEV and EV generate current in excess of 100 Amps, or 100,000 mA
Effect thresholds based on full grown adult physiology. Effects on smaller persons or
children may occur at lower amperage.
2 Personnel Protection Devices for Specific Applications, Electric Power Research Institute,
Project 6850-02, Final Report, October 1999, prepared by Underwriters Laboratories Inc.
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AC Current Effect on Humans
Milliamps (1000 mA = 1 A)
833
105
70
20
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6
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OBSERVABLE EFFECT
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2
Current Used by a 100 Watt Light Bulb
Ventricular Fibrillation
Electrical Burns
Muscle Contraction (Respiratory Paralysis)
Can’t let go
GFCI will trip
Startle Reaction
Some models of P/HEV and EV generate current in excess of 100 Amps, or 100,000 mA
Effect thresholds based on full grown adult physiology. Effects on smaller persons or
children may occur at lower amperage.
2 Personnel Protection Devices for Specific Applications, Electric Power Research Institute,
Project 6850-02, Final Report, October 1999, prepared by Underwriters Laboratories Inc.
1
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
What is the difference
between Voltage and
Current?
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Answer
Voltage is the electrical
potential of a circuit, or
the “pressure” of the
current.
Current is the rate of flow,
measured in amperes or
amps.
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
What are the two
types of electricity
used in P/HEVs and
EVs?
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Answer
Direct Current (DC)
and
Alternating Current (AC)
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
For current to flow (AC or
DC), what must be
completed?
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Answer
A Circuit or path
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
What is a major
difference between a
HV electrical system
in a car and those
found in structures?
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Answer
Vehicle HV Systems are
isolated from the chassis,
where structures’ electrical
systems are grounded to
the earth.
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
The risk of a shock
occurs when the
body becomes part
of the_________?
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Answer
Circuit
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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS
Module II: Basic Electrical Concepts and Hazards
Module Summary
● Electrical Terms.
● Types of Electricity.
● Understanding Electrical Circuits.
● Building Electrical Systems vs. Vehicle
Electrical Systems.
● How Electricity Affects the Body.
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