Hybrid Electric Vehicles Course Guide PDF

Automotive Services HYBRID ELECTRIC VEHICLES Objective One  Introduction (Hook) Hook:  Outcome Why is it important for you to learn this skill? A growing percentage of vehicles are hybrid electric vehicles (HEV) and their operation and service is notably different...

Automotive Services HYBRID ELECTRIC VEHICLES Objective One  Introduction (Hook) Hook:  Outcome Why is it important for you to learn this skill? A growing percentage of vehicles are hybrid electric vehicles (HEV) and their operation and service is notably different from non-hybrid vehicles. You need to understand how they differ to service and maintain them safely and effectively. When you have completed this module, you will be able to : Describe the operation of a hybrid electric vehicle.  Objectives At the end of this module Automotive Services Year 2 students will be able to: 1. Identify the variety of HEV designs on the market. 2. Describe the operation of an HEV. 3. Describe the interaction between the motor/generator during high voltage charging, traction torque, kinetic energy recapture (regenerative braking or engine braking) and internal combustion engine starting.  INTRODUCTION This module introduces the methods of classifying hybrid electric vehicles (HEVs), the three power flow arrangements and hybrid operating strategies. It explains how the components and systems unique to hybrid vehicles work and how they interact to make hybrid vehicles function. Although there are several different hybrid technologies in development, all references to a hybrid vehicle in this module mean an HEV. In this presentation, we cover the details of Objective 1.  Objective One: Identify the variety of HEV designs on the market. Hybrid Electric Vehicle According to the Society of Automotive Engineers (SAE) definition, a hybrid vehicle is one that has two or more energy storage systems both of which must provide propulsion power, either together or independently (Figure 1). In the case of a hybrid electric vehicle (HEV), one of these energy storage systems is a high voltage battery, while the other is a conventional hydrocarbon fuel such as gasoline, diesel, compressed natural gas (CNG) or liquefied petroleum gas (LPG).  Objective One: Identify the variety of HEV designs on the market. Hybrid Electric Vehicle Figure 1 - Hybrid vehicle with two energy sources.  Objective One: Identify the variety of HEV designs on the market. Hybrid Electric Vehicle Many hybrid technologies are currently being tested. Hydraulic hybrids that use pressurized hydraulic fluid in an accumulator, for their secondary energy storage, show substantial promise. Some Formula One racing teams began using a kinetic energy recovery system (KERS) in the 2009 racing year. In this system, a high-mass spinning flywheel stores kinetic energy during braking and then uses it during acceleration. Compressed air can also be used as an energy storage system, though no practical system has been developed for a hybrid vehicle.  Objective One: Identify the variety of HEV designs on the market. Hybrid Vehicle Rationale Hybrid vehicles are not a recent development but the current technology to make them practical for daily use is relatively new. The Toyota Prius with the Hybrid Synergy Drive system was introduced in North America in the year 2000 and represents a milestone in hybrid development (Figure 2). Since then, most automotive manufacturers have added at least one hybrid vehicle to their model lines or are in the process of developing one.  Objective One: Identify the variety of HEV designs on the market. Hybrid Vehicle Rationale Figure 2a – Toyota Synergy Drive, engine and motor.  Objective One: Identify the variety of HEV designs on the market. Hybrid Vehicle Rationale Figure 2b – Toyota Synergy Drive. Cutaway of engine, motor and drive.  Objective One: Identify the variety of HEV designs on the market. Hybrid Vehicle Rationale Reduced emissions and fuel consumption are the primary motivators for developing hybrid vehicles. Oil is a finite resource and is growing scarcer and more expensive. The desire for energy security drives governments to impose higher fuel mileage standards (Figure 3), which the automobile manufacturers strive to achieve with new technology like hybrids. Increasingly stringent emission standards also force automotive manufacturers to develop hybrid technology.  Objective One: Identify the variety of HEV designs on the market. Hybrid Electric Vehicle Figure 3 - Fuel Economy Standard chart  Objective One: Identify the variety of HEV designs on the market. Hybrid Vehicle Rationale Other reasons for hybrid electric vehicles include: A desire for cleaner air. Reduced carbon dioxide and other emissions. Less carbon usage. Reduced fuel consumption. Interest in new technology.  Objective One: Identify the variety of HEV designs on the market. HEV Definitions Electric motors can also function as generators and vice versa, so manufacturers refer to them as motor-generators (MG). If a vehicle design has more than one MG, they are numbered as MG1 and MG2. A conventional 14 volt (V) generator on non-hybrid vehicles is referred to in this module as an alternator to avoid confusion with the MG of hybrid vehicles. To differentiate between the internal combustion engine (ICE) and the electric motor/generator (MG), this module uses the term engine only for the ICE and the term motor only for an electric motor or MG.  Objective One: Identify the variety of HEV designs on the market. HEV Definitions HEVs also use two batteries, which are: 1. a conventional 12.6 V dc lead acid battery for lights, instrumentation, infotainment and comfort features (referred to as the accessory battery or 14 V system) 2. a high voltage (HV) battery for the electric traction motor (referred to as the HV battery or battery module). HEV Categories Two methods of categorizing hybrids are: 3. By power flow. 4. By the integration of hybrid-specific operating strategies.  Objective One: Identify the variety of HEV designs on the market. HEV Categories – Power Flow Configurations This category is based on how the electric motor and the internal combustion engine are able to deliver power to provide traction torque to the wheels. Hybrid drivetrains have three possible configurations: 1. Series. 2. Parallel. 3. Series Parallel.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Power Flow Configurations – Series Hybrids Series power flow (Figure 4) use only an electric motor to generate traction torque. The ICE is not coupled directly to the wheels; instead, it drives a generator to convert the power from the ICE into electrical power. This electrical power can be directed to drive the electric motor, charge the HV battery or both. Series hybrids require more powerful electric motors than parallel hybrids because the ICE does not provide any traction torque to assist the electric motor. The generator and the battery have increased capacity to provide sufficient power for the motor. Increasing the capacity of all of these components adds weight and cost. As a result, few manufacturers make series hybrids.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Power Flow Configurations – Series Hybrids Figure 4 – Series Hybrid Power Flow  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Power Flow Configurations – Parallel Hybrids In a parallel hybrid configuration (Figure 5), both the electric motor and the ICE deliver traction torque to the wheels. In some cases, either source may provide all traction torque; in other cases, only the ICE is capable of providing unassisted traction torque or both must work together at all times.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Power Flow Configurations – Parallel Hybrids Figure 5 – Parallel Hybrid Power Flow  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Power Flow Configurations – Series Parallel Hybrids Series-parallel hybrids combine features of both series and parallel drivelines (Figure 6). They can function as a series driveline, a parallel driveline or both at the same time. This configuration is by far the most common, since it provides the benefits of the other two configurations.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Power Flow Configurations – Series Parallel Hybrids Figure 6 - Series Parallel Power Flow  Objective One: Identify the variety of HEV designs on the market. Questions What are the ways to configure power flow in HEVs? Give four reasons to choose an HEV over a vehicle fitted with only an internal combustion engine. In a parallel hybrid, what delivers traction torque to the wheels?  Objective One: Identify the variety of HEV designs on the market. HEV Categories - Operation Strategies Hybrid technology allows manufacturers to add several operating features to HEVs that are generally not found or are not possible on non-hybrids. Depending on the level of hybrid technology, an HEV may have one, several or all of these features. The operating features that hybrids have are: Idle off or auto-stop and start. Electric assist. Regenerative braking. Electric vehicle (EV) mode.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Idle off or auto-stop and start The ICE shuts down when the vehicle decelerates or comes to a stop. Shutting down the ICE, when no torque is required, reduces fuel consumption and emissions. Fuel consumption reduction is usually between 3% to 5% but may be extended to 20%. The ICE restarts when it is required for acceleration, to charge the HV battery or to keep the engine at operating temperature. On hybrids that require the ICE to provide traction torque for acceleration, the ICE as quickly as the driver moves his foot from brake to accelerator pedals (1/2 second or less)  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Idle off or auto-stop and start Vehicles that can accelerate using only the electric motor may delay starting the ICE until it is required for additional torque or to generate power for the traction motor. When the ICE shuts down, any accessories that are driven by the ICE stop working as well. Typically, this would include: the hydraulic power steering pump the coolant pump the alternator the automatic transmission fluid pump the air conditioning compressor.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Idle off or auto-stop and start With the exception of the alternator, electric motor driven accessories replace the conventional components so that they can continue operating off the HV battery when the ICE shuts down. When the ICE stops, the HV battery also substitutes for the alternator through a voltage reducing circuit in the inverter or accessory power module (APM). The APM provides low voltage (13.5 to 14.5 V dc) to operate the accessories and keep the accessory battery charged.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Idle off or auto-stop and start Hybrids use an MG to replace both the starter motor and the generator used on nonhybrid vehicles. The MG is larger than either of the components it replaces and performs both functions (starting the ICE and supplying electrical power to meet the vehicle needs). NOTE Auto stop is used on some non-hybrid vehicles too. Figure 7 shows an MG used in a hybrid system called a belted alternator-starter (BAS).  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Idle off or auto-stop and start Figure 7 – An MG from a BAS system.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Electric Assist Electric assist uses stored energy from the battery to drive the electric propulsion motor during peak power operation such as accelerating or climbing a hill. The torque from the ICE and the MG combine to provide more torque at the wheels than either power source can produce on its own. This feature allows the car designer to downsize and modify the ICE to bring its power rating closer to the average power requirements of the vehicle instead of the peak power needs. Much of an average driving cycle requires less than 30 kW (40 hp), a fraction of the peak output of most modern automobile engines.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Electric Assist The extra power capacity is only used to meet peak power demands. Another benefit of electric assist becomes evident when you compare the torque curve of an electric motor to that of an ICE. Electric motors develop maximum torque at zero rpm (stall), whereas an ICE produces peak torque at much higher rpm (Figure 8). The electric motor can provide extra torque for launching the vehicle from a stop when the ICE torque output is relatively low.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Electric Assist Figure 8 – Torque and power curves of electric motors (A). Torque and power curves of ICE (B)  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Electric Assist Electric assist is a feature that only applies to parallel and series-parallel layouts since a series layout always uses the electric motor for propulsion. The equivalent of electric assist for a series hybrid occurs when the peak demand for current from the electric traction motor exceeds the capacity of the ICE driven generator. The extra current required then comes from the battery, so electric assist becomes battery assist.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Regenerative Braking Friction brakes convert a car's kinetic energy to heat and then dissipate the heat into the air. This means that all the energy used in accelerating the vehicle is lost when the vehicle slows to a stop using the brakes. Regenerative braking recaptures the kinetic energy of the vehicle (Figure 9) during deceleration by converting it into electrical energy and then storing this energy by charging the high voltage battery.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Regenerative Braking Figure 9 - Regenerative braking recaptures kinetic energy.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Regenerative Braking Recapturing the kinetic energy of the vehicle during braking reduces the vehicle's overall fuel consumption. The main benefit of regenerative braking occurs during stop and go conditions or on hilly or winding roads. This is why most hybrid vehicles' fuel consumption is lower for city driving than for highway driving.  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Electric Vehicle (EV) Mode In electric vehicle (EV) mode, the ICE does not run and contributes no power to the driveline. The electric traction motor alone drives the wheels. The energy to propel the vehicle comes entirely from the HV battery (Figure 10). The range and speed of the vehicle in EV mode depends largely on the energy storage capacity of the battery. Most hybrids are ICE dominant; they are only able to travel 1 to 5 km in EV mode before the HV battery is depleted to the point that the battery management computer shuts down the HV system, usually around 40% state of charge (SOC).  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Electric Vehicle (EV) Mode Figure 10 – Electric Vehicle (EV) Mode  Objective One: Identify the variety of HEV designs on the market. HEV Categories: Operation Strategies Electric Vehicle (EV) Mode Some hybrids are EV dominant, meaning they operate in electric mode under most driving conditions for up to 80 km (50 mi). One manufacturer calls this hybrid an extended range electric vehicle (E-REV), but it fits the SAE definition of a hybrid vehicle.  Objective One: Identify the variety of HEV designs on the market. Questions How are HEVs categorized? What are the four operation strategies of HEVs? What is the purpose of regenerative braking?  Objective One: Identify the variety of HEV designs on the market. Micro Hybrids Micro hybrids do not fit the SAE definition of a hybrid vehicle because the MG does not contribute torque for traction; therefore micro hybrids do not have two sources of energy to propel the vehicle. They use idle stop and in some cases regenerative braking, which are hybrid vehicle features. In a micro-hybrid, a single MG replaces both the starter and the alternator found in a conventional vehicle.  Objective One: Identify the variety of HEV designs on the market. Micro Hybrids A special belt and tensioner allow the MG to drive either the engine for starting or be driven by the engine for charging. This is very similar to the BAS system, however the MG operates on a regular 12.6 V lead acid battery; there is no HV system. When the vehicle is slowing down with a closed throttle, the MG may function as a generator, adding load to the engine to turn the vehicle's kinetic energy into electrical energy and charge the battery (regen).  Objective One: Identify the variety of HEV designs on the market. Mild Hybrids Mild hybrid vehicles generally use a parallel power flow arrangement. They make use of idle off, regen and electric assist, but are not capable of operating in EV mode. Mild hybrids have HV systems that operate below 150 V dc, with the most common systems using a 42 V dc system. Some early mild hybrids did not use electric motor driven air conditioning compressors. On such vehicles, the engine idle stop feature will not shut the engine off if the air conditioning compressor is enabled.  Objective One: Identify the variety of HEV designs on the market. Mild Hybrids The MG on a mild hybrid replaces both the starter motor and the alternator. One style of MG is actually an upsized alternator that has been modified to allow it to function as a motor as well. Regen braking on mild hybrids is often limited to engine braking, which does not interact with the friction brakes. Mild hybrids that regen with brake pedal application do so in a parallel fashion, meaning both the regen and the hydraulic brake systems apply at the same time.  Objective One: Identify the variety of HEV designs on the market. Strong Hybrids Strong hybrids (full hybrids) are generally series-parallel power flow designs. They incorporate all of the same features as a mild hybrid (idle off, regen and electric assist) with the addition of EV mode. The brake system on strong hybrids use a series application; regen braking applies first up to a programmed braking threshold, then the friction brakes begin to assist for more aggressive braking and braking below approximately 8 kph (5 mph). Light to moderate braking is almost entirely regen, meaning conservative driving can recapture substantial amounts of energy that would otherwise be lost as heat in the friction brakes.  Objective One: Identify the variety of HEV designs on the market. Strong Hybrids Electric assist in a full hybrid may provide upwards of 80 kW (60 hp) of power to assist the ICE in propelling the vehicle. The torque and power curve of the electric motor is ideal for low speed launch, while the ICE is best suited to provide power at higher speeds, when the power from the motor starts to drop off.  Objective One: Identify the variety of HEV designs on the market. Strong Hybrids The EV mode range and speed depend primarily on whether the vehicle is ICE dominant or EV dominant. Within those two categories, the range and speed vary principally on the battery energy storage capacity and the design of the driveline Hybrids that are EV dominant may travel in EV mode at speeds up to 160 kph (100 mph). At lower speeds, the EV mode distance range for some is over 175 km (109 miles). Hybrids that are ICE dominant generally operate in EV mode at speed below 50 kph (30mph) and have an EV range below 8 km (5 mi).  Objective One: Identify the variety of HEV designs on the market. Plug-in Hybrids Some strong hybrids can charge their batteries off of the electric grid, particularly EV dominant hybrids. ICE dominant plug-in hybrids usually have more energy storage capacity than equivalent non-plug vehicles, which extends their EV range. A special charging plug (Figure 11) connects the vehicle to a charging station on a dedicated circuit. This means the ICE will operate for less time or not at all, which reduces fuel consumption. Figure 11 – Plug in hybrid charging connector  Objective One: Identify the variety of HEV designs on the market. Designs The type and location of the electric motor makes four general layouts or designs possible for hybrid vehicles. The layouts are: 1. transaxle motors, 2. flywheel motors, 3. belted alternator-starters and 4. wheel hub motors.  Objective One: Identify the variety of HEV designs on the market. Designs – Transaxle Motors Series-parallel hybrids incorporate two MGs (MG1 and MG2) into the transmission or transaxle assembly (Figure 12). In the most basic design, a single planetary gear set couples the MGs and the ICE to the wheels. No holding clutches are used to provide reaction torque to the gear set members; instead, the components attached to them provide the reaction torque. Figure 12 – Transaxle motors  Objective One: Identify the variety of HEV designs on the market. Designs – Transaxle Motors Other variations of this design add holding clutches and more planetary gear sets to improve efficiency or add more control of the gear ratios that drive the motor generators. For four-wheel drive capability, a third MG (mounted in the rear axle assembly) eliminates the mechanical connection between the ICE and the rear wheels; these are called through the road hybrids. The electric motors (Figure 13) are three-phase, AC motors. Various names are used, sometimes relating to minor design variations. Common names for the motors include switched reluctance motors, synchronous ac motors and rotating field motors.  Objective One: Identify the variety of HEV designs on the market. Designs – Transaxle Motors Figure 13 – Electric motor construction  Objective One: Identify the variety of HEV designs on the market. Designs – Transaxle Motors The motors consist of a stator assembly with multiple poles, wound with three separate field windings spaced at 60° intervals. Inside the stator assembly is an armature made with strong rare-earth magnets creating evenly spaced poles around the circumference of the armature. A rotational sensor or indexing device called a resolver (Figure 14A) mounts to the armature shaft to provide the motor controller with high resolution armature position data (Figure 14B). This data is required so the controller knows which field winding to energize and in which polarity.  Objective One: Identify the variety of HEV designs on the market. Designs – Transaxle Motors Figure 14 – Resolver (A) and Signal (B)  Objective One: Identify the variety of HEV designs on the market. Designs – Transaxle Motors The motor controller switches the three phase windings on and off while also reversing their polarity in a sequence that creates a rotating magnetic field in the stator. The permanent magnets in the armature are attracted to the rotating field, causing them to develop torque to turn the armature. As the armature turns, the controller regulates the speed and strength of the rotating stator field to keep the armature rotating in an attempt to catch up to the stator field. The difference between the stator field and the armature field is called motor slip.  Objective One: Identify the variety of HEV designs on the market. Designs – Transaxle Motors Motor speed is controlled by the frequency of the ac going to the stator, while motor torque is controlled by the strength of the magnetic field in the stator windings. The stator field strength is a function of the amount of current flow. The controller can orient the stator field to create slip in either direction, so the motor is reversible.  Objective One: Identify the variety of HEV designs on the market. Power Split Devices The planetary gear set connects the transmission or transaxle mounted motors and the ICE to become a power split device (PSD). This is a planetary gear set dividing torque similarly to a differential, with the internal gear and sun gear as the axle gears and the carrier and planet gears as the differential case and pinion gears (Figure 15). The difference in size and tooth count between the sun and the internal gear produces an uneven torque split, meaning the carrier delivers more torque to the internal gear than it does to the sun gear.  Objective One: Identify the variety of HEV designs on the market. Power Split Devices Figure 15 – The PSD compared to Differential  Objective One: Identify the variety of HEV designs on the market. Power Split Devices The crankshaft of the ICE couples directly to the carrier of the planetary gear set. The sun gear couples to MG1, while the internal gear couples to MG2 and to the output to the final drive (Figure 16).  Objective One: Identify the variety of HEV designs on the market. Power Split Devices Because MG2 couples to the final drive, it delivers torque directly to the final drive when MG2 is in motoring mode. If the ICE produces torque, it adds to the torque that MG2 produces. The ratio of the power split device (Figure 17) determines how much engine torque the ICE delivers through this path, which is generally around 70%. The remaining 30% of the ICE torque drives the sun gear, which turns MG1.  Objective One: Identify the variety of HEV designs on the market. Power Split Devices Figure 17 – Ratio of power split device  Objective One: Identify the variety of HEV designs on the market. Power Split Devices In regen (Figure 19), torque from the wheels drives MG2 as a generator without any interaction with the planetary gear set. If the ICE is stopped, the PSD transfers torque to MG1 through the ring gear, allowing it to participate in regen in some situations. This can occur even when the engine is running as long as the speed of the internal gear and the ICE combine to keep the sun gear turning.  Objective One: Identify the variety of HEV designs on the market. Power Split Devices Figure 18 – Power Flow in PSD through Regen  Objective One: Identify the variety of HEV designs on the market. Power Split Devices Torque from MG1 controls the speed and direction of the sun gear. When the ICE runs, MG1 torque determines how much engine torque transfers through the PSD to the ring gear. With the vehicle stopped and the ICE at idle, MG1 is allowed to free wheel, which means it requires very little torque. Engine torque output is low, so minimal torque transfers to the ring gear (wheels). This provides the equivalent of a neutral gear, since the engine cannot be decoupled from the driveline any other way. To prevent damaging MG1, the computer limits engine speed so as to not spin MG1 faster than 6500 rpm.  Objective One: Identify the variety of HEV designs on the market. Power Split Devices When the vehicle is moving, the computer controls the torque required to spin MG1 by configuring it as a generator and varying the load applied to it, directing the generated power to drive MG2. As the generator load on MG1 increases, the amount of torque required to drive it increases. The computer regulates the ICE throttle to maintain sufficient torque input to MG1, which also regulates the ICE torque applied to the internal gear according to the power split ratio (Figure 19). Thus, torque from the ICE adds to the torque from MG2 to drive the wheels.  Objective One: Identify the variety of HEV designs on the market. Power Split Devices Figure 19 – Power flow through PSD with ICE driving MG1  Objective One: Identify the variety of HEV designs on the market. Power Split Devices As MG1 transitions from freewheeling down towards engine rpm, the effective ratio of the PSD changes along with it. When MG1 reaches the same rpm as the ICE, the ratio between the ICE and the output is 1:1. Decreasing the speed of MG1 below ICE rpm moves the PSD into an overdrive ratio (Figure 20). The computer can also configure MG1 as a motor and drive it in the opposite direction from the carrier, allowing it to add power to the wheels. Using MG1 to control the speed and direction of the sun gear produces a continuously variable ratio, limited by the maximum clockwise and counter-clockwise rotational speeds of MG1.  Objective One: Identify the variety of HEV designs on the market. Power Split Devices Figure 20 – PSD in overdrive ratio  Objective One: Identify the variety of HEV designs on the market. Designs – Flywheel Motors Hybrids with a flywheel motor add motor torque at the transmission input shaft. The motor armature is built into the engine flywheel and uses a flat pancake stator between the engine and the transmission (Figure 21). Motor speed is limited to engine speed and there is no torque splitting. Torque output of the motor is controlled entirely by varying the power input. The motor stator may also be incorporated into the torque converter on some designs.  Objective One: Identify the variety of HEV designs on the market. Designs – Flywheel Motors Figure 21 – Flywheel mounted pancake MG design  Objective One: Identify the variety of HEV designs on the market. Designs – Flywheel Motors Variations on this design include adding a clutch or clutches to de-couple the engine and motor, which allows more versatility. This design enables the vehicle to operate in EV mode, since large power losses in turning the engine are eliminated. Regen braking can also be enhanced by using the MG to absorb all of the brake energy instead of it going to engine pumping loss.  Objective One: Identify the variety of HEV designs on the market. Belted Alternator-Starters A belted alternator-starter design (BAS) is an MG coupled to the engine by a belt, which is the simplest and cheapest way to hybridize a vehicle. Power flow is strictly parallel since there is only one MG which can only perform one function (motor or generator) at a time. This system is not used for strong hybrids. The MG is very similar to an upsized alternator found on non- hybrids (Figure 22). It uses a three-phase stator winding and a claw-style armature (rotor). The armature’s field may come from permanent magnets or from an excited field winding.  Objective One: Identify the variety of HEV designs on the market. Belted Alternator-Starters When operating as a generator, the motor controller rectifies the stator output into dc. To operate the MG as a motor, the controller switches the stator phases in sequence to drive the armature. A resolver provides armature position data for the motor controller. Figure 22 – A BAS Alternator  Objective One: Identify the variety of HEV designs on the market. Belted Alternator-Starters The drive belt is a special high-tension poly-ribbed belt. It wraps 180 degrees or more around the MG pulley (Figure 24) to assure maximum traction between the pulley and the belt. A special tensioner maintains the correct tension on the belt. Figure 23 – Belt wrap on a BAS system  Objective One: Identify the variety of HEV designs on the market. Belted Alternator-Starters These MGs develop very high torque output, typically in excess of 10 hp. This is necessary to spin the engine up to a minimum of 600 rpm within 400 milliseconds (ms). This same power output is available for electric assist. Wheel Hub Motors Wheel hub motors (Figure 24) may be used on either a series or a series-parallel hybrid. They can also be installed on the rear wheels only for a through the road hybrid. Wheel hub motors vehicles have some unique benefits and problems.  Objective One: Identify the variety of HEV designs on the market. Wheel Hub Motors On the beneficial side, wheel hub motors allow very precise control of the torque and speed at each wheel of the vehicle. This is beneficial for acceleration, cornering and braking. They can also free up space normally taken by a transmission or transaxle, although they take up more space in the wheel centres than brakes alone do. Figure 24 – Wheel hub motor  Objective One: Identify the variety of HEV designs on the market. Wheel Hub Motors Wheel hub motors have several problems included below: Wheel hub motors increase unsprung weight at the wheels, which can affect ride and handling. Wheel hub motors are subject to severe pounding action when the vehicle travels over rough roads. Wheel hub motors are exposed to road splash including dirt, gravel, water and salt. Wheel hub motors require individual HV wiring to each MG location. Wheel hub motors must withstand the high temperatures of friction brakes.  Objective One: Identify the variety of HEV designs on the market. Questions With regard to belted alternator-starters, what regulates the stator output to dc?  REFERENCES Hybrid Electric Vehicles © 2014, Her Majesty the Queen in right of the Province of Alberta. Figure 2a – Pepper-Land Media Figure 2b – Pepper-Land Media Figure 9 – Chrysler Group LLC Figure 12 – Chrysler Group LLC Figure 13 – General Motors Canada Ltd Figure 14 (A & B) – Chrysler Group LLC Figure 21 – American Honda Motor Co, Inc. Figure 23 – Gates Canada INC.  Thank You Any Questions?