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NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS Module II: Basic Electrical Concepts And Hazards 2-1 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. 2-2 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 2-3 Basic Electrical Terms Voltage: Electrical Potential • Comparable to water pressure or PSI in a hose. • Measured in Volts. 2-4 Basic Electrical Terms Current: Quantity of electrons flowing • Comparable to the rate of flow of water or gallons per minute (GPM). • Measured in Amperes. 2-5 Basic Electrical Terms Resistance: A material’s opposition to conducting current • Comparable to friction loss in hose lines or appliances. • Measured in Ohms. 2-6 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. 2-7 DIRECT CURRENT VS. ALTERNATING CURRENT Direct Current Current always flows in the same direction. Alternating Current Current repeatedly reverses direction. 2-8 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. 2-9 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. 2-10 NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS Module II: Basic Electrical Concepts and Hazards Video Electrical Circuits 2-11 NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS Module II: Basic Electrical Concepts and Hazards Video Electrical Circuits 2-12 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 2-13 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 2-14 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. 2-15 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. 2-16 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. 2-17 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. 2-18 DC Current Effect on Humans Milliamps (1000 mA = 1 A) 240 70 40 2 1 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. 1 2-19 AC Current Effect on Humans Milliamps (1000 mA = 1 A) 833 105 70 20 6 6 .5 OBSERVABLE EFFECT 1 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 2-20 NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS Module II: Basic Electrical Concepts and Hazards What is the difference between Voltage and Current? 2-21 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. 2-22 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? 2-23 NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS Module II: Basic Electrical Concepts and Hazards Answer Direct Current (DC) and Alternating Current (AC) 2-24 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? 2-25 NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS Module II: Basic Electrical Concepts and Hazards Answer A Circuit or path 2-26 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? 2-27 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. 2-28 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_________? 2-29 NFPA ELECTRIC VEHICLE SAFETY FOR EMERGENCY RESPONDERS Module II: Basic Electrical Concepts and Hazards Answer Circuit 2-30 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. 2-31