`
`TOR-0059(G769-OI) -2. VOL.
`
`I
`
`Final Report
`
`Hybrid Heat Engine / Electric Systems Study
`
`Volume I: Sections 1 through [3
`
`71 }UN ¢1
`
`Prepared for DIVISION OF ADVANCED AUTOMOTIVE
`POWER SYSTEMS DEVELOPMENT
`
`U. S. ENVIRONMENTAL PROTECTION AGENCY
`
`Ann Arbor, Michigan
`
`Contract No. F04701-70-C-0059
`
`@
`
`Office of Corporate Planning
`THE AEROSPACE CORPORATION
`
`El Segundo. California
`
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`Report No.
`TOR-0059(6769-01)-2,
`Vol.
`1
`
`FINAL REPORT
`
`HYBRID HEAT ENGINE/ELECTRIC SYSTEMS STUDY
`
`Volume 1: Sections 1 through 13
`
`71 JUN (61
`
`Office of Corporate Planning
`THE AEROSPACE CORPORATION
`
`El Segundo, California
`
`Prepar ed for
`
`Division of Advanced Automotive Power Systems Development
`U. S. ENVIRONMENTAL PROTECTION AGENCY
`
`Ann Arbor, Michigan
`
`Contract No. F04701-70-C-0059
`
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`FOR EW OR D
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`Basic to analyzing the performance of the hybrid vehicle was the importance
`of understanding the characteristics of each major component since each
`would be operating in a nonstandard mode required by the hybrid arrange-
`ment.
`in addition,
`the potential for improvement had to be understood to
`predict the performance of advanced designs. This report,
`therefore, con-
`tains two types of information:
`(a) hybrid system analysis and results; and
`‘(b) major component state-of-the-art discussions, characteristics used in
`this study, and advanced technology assessments. Heat engine operating
`characteristics, mechanical parameters, and exhaust emissions are covered
`extensively because of both their primary importance and the difficulty
`involved in collecting a reliable comprehensive set of data; this should relieve
`future investigators making studies of nonconventional propulsion systems of
`the necessity of repeating the burdensome task of assembling a data bank.
`
`It should be recognized that calculated results are- based on data compiled in
`this study. The magnitude and trends were established on the basis of a
`comprehensive survey and evaluation of the best data from both the open
`literature and current available unpublished data sources. These data are
`considered suitable for use in the feasibility study conducted under this run;
`tract. However, for further detailed design a substantial refinement of the
`data base would be necessary.
`
`he report is organized to give a logical build-up of information starting with
`study specification, analytical techniques, and component characteristics and
`concluding with system performance results and recommendations [or develop-
`ment. However, selective reading of major systems performance results is
`possible and to assist those so interested,
`the following brief guide is pre—
`sented:
`
`Section 1
`
`Summary of study results and recom-
`mentations
`
`Sections 2, 3, 10, and 11
`
`Sections 3 and 4
`
`Sections 6 through 9
`
`Section [2
`
`Section 13
`
`Presentation of study objectives,
`design specifications, and results
`
`Description of computational techniques
`and performance requirements
`
`Review of contemporary and projected
`technology of major components
`
`Cost estimates for high—volume pro—
`duction of hybrid cars
`
`Presentation of a technological plan for
`component and system development
`
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`This report is published in two volumes for convenience; however, separation
`of the material is made with due regard to organization. Volume 1 consists of
`Sections 1 through 13 and presents the essential study information, while
`Volume 11 consists of Appendices A through F and presents supplementary
`data.
`a
`
`The period of performance for this study was June 1970 through June 1971.
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`AC KNOW LE 00 NlEN TS
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`The extensive diversity in technological capabilities necessary for a thorough
`
`evaluation of the hybrid electric vehicle has required the reliance for support
`
`and expertise on select members of The Aerospace Corporation technical
`staff as well as members of the national technical community. Recognition
`
`of this effort is expressed herewith:
`
`The Aer os pace Cor por ation
`
`Mr. Dan Bernstein
`Mr. Lester Forrest
`Mr. Gerald Harju
`
`Mr. Merrill Hinton
`
`Dr. Toru Iura
`
`Electrical System-Control System
`Heat Engines (Internal Combustion)
`Programming for Computations
`
`Vehicle Specifications/Conceptual Design
`and Sizing Studies
`Heat Engines (Internal Combustion‘)
`Heat Engine Exhaust Emissions
`Vehicle Exhaust Emissions Test Program
`
`Mr Dennis Kelly
`
`Electrical System — Motor and Generator
`
`Mr. Jack Kettler
`
`Mr. Harry Killian
`
`Electrical System — Batteries
`Heat Engines (External Combustion)
`
`Computational Techniques
`Electrical System - Batteries
`
`Mr. Robert La France
`
`Electrical System - Motor, Generator,
`Control Systems
`
`Mrs. Roberta Nichols
`
`Vehicle Exhaust Emission Test Program
`
`Mr. Wolfgang Roessler
`
`Heat Engine Exhaust Emissions
`Vehicle Exhaust Emission Test Program
`
`Dr. Henry Sampson
`
`Vehicle Specifications
`Computational Techniques
`Vehicle Power Requir ements
`
`Mr. Raymond Schult
`
`Electrical System - Motor, Generator,
`Control Systems
`
`University of California, Berkeley
`
`Dr. Robert Sawyer
`
`Heat Engine Exhaust Emissions
`
`University of California,
`
`Irvine
`
`Dr. Robert M. Saunders
`
`Electrical System - Motor Generator,
`Control Systems
`
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`It is to be noted that considerable data of great value to this study were
`
`kindly provided by individuals in industry, universities, and government
`
`agencies. Acknowledgment of these data sources is given in Appendix F
`
`to this report.
`
`Donald E. Lape es
`Manager, Hybrid Vehi
`
`e Program
`
`
`
`
` ir ctor, Pollution and Resources
`rograms
`Office of Corporate Planning
`
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`SECTION 10
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`CONCEPTUAL DESIGN AND SIZING STUDIES
`
`10. l
`
`CONCEPTUAL DESIGNS
`
`10. 1. 1
`
`Introduction
`
`Heat engine/electric hybrid powerplant concepts can be grouped into two
`
`broad classes: series and parallel configurations, as previously defined in
`
`Section 3 and further discussed in Section 6.
`
`In all cases,
`
`the difference between power required for vehicle propulsion
`
`and power supplied by the heat engine must be supplied by the batteries.
`
`Hence, at the cutset,
`
`it shOuld be rec0gnized that Once the vehicle maximum
`
`power requirements have been established,
`
`the battery design goals can be
`
`markedly influenced by the heat engine power output profile. This effect is
`
`shown in Fig. 10-1 where vehicle maximum power (for maximum acceleration)
`
`and cruise power requirements are illustrated, along with three different
`
`vehicle -velocity varying power profiles delivered by the heat engine. Pro-
`
`file #2 is defined as that power output profile which will result in the batteries
`
`being fully recharged at the end of the driving cycle.
`
`It is clear that profile #1 imposes far less severe requirements on the battery
`
`(in terms of power demand) than profiles #2 and #3, but it also requires a
`
`higher level of sustained heat engine power output at lower vehicle Speeds. and
`
`is in excess of that heat engine power level required to maintain the battery
`
`state—of-charge,
`
`thus resulting in higher heat engine exhaust emissions and
`
`increased fuel consumption.
`
`An alternative type of power profile to those shown in Fig. 10-1 can be en-
`
`visioned wherein the heat engine is required to accelerate (change power output)
`
`rapidly, as in c0nventional SI engine-powered vehicles. The heat engine could
`
`have a power output profile similar to profile #3 for constant velocity operation,
`
`and aCCelerate to a maximum power level (similar to the level of profile #1)
`
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`during periods of vehicle acceleration,
`
`thus reducing battery peak demand
`
`requirements. However, for purposes of this study,
`
`it was assumed that
`
`this form of engine performance might not be attainable with low—pollution
`
`engines with possible "driveability" (i. e. , smooth power—output profiles
`
`under instantaneous load changes) constraints.
`
`Therefore, all subsequent discussion is directed toward conceptual approaches
`
`in which heat engines are not subjected to large instantaneous changes in power
`
`output.
`
`In the following illustrative cases which depict power output varying
`
`with time, vehicle velocity, or step changes,
`
`it is assumed that these power
`
`changes take place over finite time intervals commensurate with the acceler—
`
`ation capability of the engine under load.
`
`MAXIMUM POWER REQUIRED
`(MAXIMUM VEHICLE ACCELERATION)
`
`MAXIMUM
`POWER SUPPLIED
`BY BATTERIES
`
`POWER
`
`HEAT ENGINE POWER PROFILE
`
`MAXIMUM REQUIRED
`CRUISE SPEED
`
`SPEED
`
`Figure 10-1. Effect of Heat Engine Power Profile on
`Required Maximum Battery Power
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`10. l. 2
`
`Series Configuration
`
`10. 1.2.1
`
`Basic Subsystems/Components
`
`_A heat engine/electric hybrid powerplant configured for the series mode, as
`
`defined above, requires certain basic subsystems/components which can
`
`vary as to type and/or number according to designer's choice.
`
`For example, a single electric drive motor can be utilized with a central
`
`differential drive to the driving wheels, or multiple drive motors could be
`
`used with a drive motor at each wheel, negating the need for the differential
`
`drive. However, aside from this configurational design Option,
`
`the remaining
`
`options in the series configuration primarily center around selection of the
`
`specific type of subSystem/component to be used, and the control system to
`
`be used for the preferred mode of Operation.
`
`The selected Series configuration used as a baseline in the present study for
`all vehicles is as shown in Fig. 10-2.. A single electric drive motor is used
`
`to supply power to the rear wheels through a central differential drive unit.
`
`Where appropriate,
`
`the differential drive unit is envisioned to contain an
`
`overdrive unit to provide a step change in electric drive motor rpm to allow
`
`high-speed cruising at near-maximum drive motor efficiency levels.
`
`The generator is mechanically-driven by the heat engine thrOugh a gearbox
`
`(Speeder/reducer) which allows the generator (or alternator as the case may
`
`be) and the heat engine to operate at different rpm levels. The other two
`
`major subsystems (i. e., battery, control system) are then electrically-
`
`connected to the generator and drive motor as schematically represented in
`
`Fig. 6-1.
`
`10.1. 2. 2
`
`Operational Modes
`
`With the foregoing series configuration arrangement, a number of modes of
`
`operation are conceivable. Several of the more significant modes are shown
`
`in Fig. 10-3 and discussed in the following paragraphs in terms of the mode
`
`of operation of the heat engine. The heat engine mode of operation was
`
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`selected as the descriptor in that heat engine exhaust emission determination,
`
`a principal objective of this study,
`tor.
`
`is more directly-relatable to this descrip—
`
`10. 1. 2. 2. l
`
`Constant Speed (rpm) and Power Output
`
`10. l. 2. 2. l. 1
`
`Heat Engine Operated Continuously
`
`In this mode of operation, a severe problem arises in relation to sizing the
`
`heat engine.
`
`If the heat engine is sized only to produce a total energy required
`
`in the time duration of the emission driving cycle (including inefficiencies of
`
`the powerplant system),
`
`then the heat engine may not pr0vide the proper
`
`continuous high-speed power demand for highway operation. This results in
`
`discharge of the batteries at high speeds (if the heat engine size is too
`
`small). Conversely,
`
`if the heat engine is sized for the maximum continuous
`
`power demand for highway operation, excessive energy loss to a heat-dump
`
`can occur (if heat engine size is too large).
`
`This mode of heat engine operation is of course attractive from the stand-
`
`point of heat engine exhaust emissions per se,
`
`in that it should be possible
`
`to select an operating point (i. e., rpm, air/fuel ratio, etc.) most amenable
`
`to reduced emissions. However,
`
`its apparent inflexibility with regard to
`
`heat engine sizing and meeting both design driving cycle as well as emission
`
`driving cycle vehicle performance led to its discard as a viable series mode
`
`of Operation for the particular classes of vehicles under consideration.
`
`However,
`
`this mode may still be suitable for vehicles with reduced t0p
`
`speeds and/or revised specification requirements.
`
`10.1. 2. 2.1. 2
`
`On-OH 92eration of Heat Engine
`
`As an alternative to continuous operation,
`
`it is possible to operate a constant
`
`power output heat engine in an “on-off" mode. Here,
`
`the heat engine would
`
`be sized to meet the continuous high—speed power demand for highway opera-
`
`tion, and would Operate intermittently during urban driving conditions. The
`
`heat engine could be turned on or off in response to (a) a battery voltage and/
`
`or state-of-charge signal,
`
`(b) a power demand from the electric drive motor,
`
`or (c) a combination of both.
`
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`In this manner, various total energy requirements can be matched by the
`
`”pulse" mode operation of the heat engine, which would allow the engine to
`
`be off more in low-energy portions of urban driving cycles.
`
`Preliminary calculations, however,
`
`indicated that this mode of operation
`
`resulted in very high energy losses during those time periods when drive
`
`motor demand is low due to battery charge rate limitations,
`
`i. e., a good
`
`portion of heat engine power output must be dumped because the battery
`
`simply cannot accept the power at the rate being supplied. This same
`
`limitation applies to the continuous heat engine operation mode previously
`
`dis cussed.
`
`There is one further disadvantage of intermittent or on-off operation. When
`
`operating continuously, power from the heat engine/generator can go directly
`
`to the drive motor during periods of power demand and bypass the battery
`
`loop entirely. When operating in the on-off mode,
`
`it would only be fortuitous
`
`if drive motor power demand occurred at the same time the engine was on.
`
`Therefore, more of the heat engine power output flows through the battery
`
`circuit in the ”on-off" mode than in the continuous operation mode. Even if
`
`battery recharge efficiency is high,
`
`the on-off mode of operation would be
`
`less efficient than the continuous mode of operation.
`
`It was concluded that
`
`while on—off operation of the heat engine at constant power output was more
`
`flexible than continuous operation at constant power output,
`
`it was not
`
`adequate for the wide range of vehicle driving requirements under considera-
`tion.
`
`10. l. 2. 2. 2
`
`Variable Power Output
`
`10. l. 2. 2. Z. 1
`
`Heat Engine Operated Continuously
`
`Many of the deficiencies of. the constant-power output mode of operation can
`
`be avoided by allowing the power output of the heat engine to vary.
`
`In this
`
`case,
`
`the heat engine can be sized for the maximum continuous power
`
`requirement and allowed to operate at lower power levels for those periods of
`
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`vehicle driving cycles which require less power.
`
`If heat engine rpm is also
`
`allowed to vary to produce this variation in power output (as in conventional
`
`internal combustion engines),
`
`it is envisioned that the control system can
`
`effectively vary throttle setting reSponse time constants so that engine rpm
`
`and power changes take place at a controlled rate in such a manner that no
`
`true vehicle acceleration demands are imposed on the heat engine in the
`
`conventional sense.
`
`Such a mode of operation would allow the energy requirements of a variety
`
`of urban driving cycles to be more closely matched (than with constant power
`
`output mode), although the matching of all duty cycle energy requirements
`
`may not be possible. To overcome this difficulty,
`
`it has been suggested
`
`that the heat engine power output be scheduled as a function of vehicle
`
`velocity (heat engine produces more power as road load increases) with a
`
`throttle "bias" feature in the heat engine fuel control system to increase or
`
`lower the baseline heat engine power output schedule in accordance with an
`
`input signal related to battery voltage and/or state-of—charge as illustrated
`
`in Fig. 10-4.
`
`With these features,
`
`the continuous operation of the heat engine on a variable
`
`power output basis appears to be a highly versatile and accommodating mode
`
`of operation for the series configuration of a heat engine/electric hybrid
`
`powerplant.
`
`10.1.2.2.2.2
`
`"Step—Mode" Operation
`
`Another technique for varying heat engine power output is to schedule power
`
`output in discrete steps. Figure 10-5 illustrates one such approach, wherein
`three levels of power output are used. A "low" level would be scheduled
`
`for a low—velocity range (e.g., 0-30 mph), an "intermediate" level for
`
`velocities between the low-velocity range and vehicle t0p speed, and a "peak"
`
`level for cruising at maximum continuous power conditions.
`
`Again, battery voltage and/or state-of-charge signals could be used to over-
`
`ride the nominal schedule of power output versus velocity.
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`10. l. 2. 2. 3
`
`Selected Baseline Operational Mode
`
`On the basis of the discussion of characteristics, advantages, and disad-
`
`vantages,
`
`the variable power output mode with the heat engine operating
`
`continuously throughout the driving cycle was selected for the series con-
`
`figuration. More specifically,
`
`the heat engine power output was tailored in
`
`accordance with vehicle velocity as shown in Fig. 10-6. The specific heat
`
`engine power output profile for each vehicle is a function of the power
`
`required for steady road load above a certain vehicle velocity. Below this
`
`the power output is at a constant value. This value is determined
`velocity,
`uniquely for each. vehicle as the value required to result in the battery being
`
`returned to its initial state-of—charge at the end of the vehicle driving cycle.
`
`The more sophisticated approach of having battery voltage and/or state-of-
`
`charge override this value as depicted in Fig. 10-4, while offering greater
`
`system flexibility, falls outside the scope of the current study.
`
`10.1. 3
`
`Parallel Configuration
`
`10.1. 3.1
`
`Basic Subsystems/Components
`
`A heat engine/electric hybrid powerplant configured for the parallel mode
`
`requires the same basic subsystems/components as the series mode plus
`
`the additional need for a transmission or gearbox for the mechanical drive
`
`from the heat engine to the differential drive and/or wheels. However,
`
`the
`
`sizing criteria for some subsystems are very different from those in the
`
`series mode. For example,
`
`the drive motor in the series case must be
`
`sized to provide all power required at the wheels.
`
`in the parallel case,
`
`the
`
`drive motor is supplementary to the mechanical power supplied by the heat
`
`engine, and is sized to provide acceleration torques on an intermittent basis,
`
`not continuous duty. The generator in the series case is sized to accommo-
`
`date full power output of the heat engine, while in the parallel case the
`
`generator is sized on the basis of heat engine minimum operating power level.
`
`The size of the heat engine required can differ between the two concepts,
`
`depending upon the particular subsystem efficiencies assumed. The particular
`
`choice of mechanical arrangement of the heat engine, generator, transmission/
`
`gearbox, and drive motor can also result in the requirement for more than one
`
`drive motor, or for the drive motor to have the dual function of motor and
`
`generator (motor /gener ator ).
`
`10-11
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`Because of the wide variation in mechanical approaches possible for the
`
`parallel configuration, a simple concept was selected for the baseline parallel
`
`configuration in the present study which more readily allowed for a direct
`
`comparison of the inherent features of the parallel versus series approach in
`
`terms of heat engine power/energy requirements and resultant exhaust
`
`emissions over the emission driving cycles. A discussion of various parallel
`
`configurations can be found in Section 6.
`
`As shown in Fig. 10-7,
`
`the baseline parallel conCept utilizes an autOmatic
`
`transmission to provide the mechanical drive connection from the heat engine
`
`to a differential drive unit powering the drive wheels. The electric drive
`
`motor, used for vehicle acceleration torque demands,
`
`is geared to the output
`
`shaft of the transmission. The generator is similarly geared to the output
`
`shaft of the heat engine. The control system is postulated to have the capa-
`
`bility to synchronize the input and output rpm's of the automatic transmission
`
`(by controlling heat engine rpm, generator load, and drive motor rpm) to the
`
`extent they are essentially equal and that fluid coupling losses are minimal
`
`(i. e. , no torque amplification used).
`
`In this concept,
`
`the generator can supply power to the batteries when heat
`
`engine power is in excess of wheel demand, and the drive motor can also
`
`function as a generator during periods of deceleration,
`
`if desired (regenera-
`
`tive braking). Additionally,
`
`the drive motor could also function as a
`
`generator during vehicle cruise periods if the heat engine power output was
`
`prescheduled or "biased" via the throttle schedule in the control system to
`
`provide more power at any given speed than required by the vehicle for road
`
`load power. Conceptually,
`
`the baseline parallel system provides all of the
`
`operational attributes postulated for the various single motor parallel concepts.
`
`10. l. 3. 2
`
`Operational Modes
`
`With the parallel configuration arrangement, a single mode of‘operation was
`
`selected as most compatible with the hardware arrangement and as providing
`
`an equitable comparison with the operational mode selected for the baseline
`
`series configuration. _As shown in Fig. 10-8,
`
`the total power output of the
`
`heat engine is scheduled as a function of vehicle velocity, with that portion
`
`above a certain velocity equal to the steady road load power. Below this
`
`velocity, a minimum power level, constant with velocity,
`
`is Selected. The
`
`10-13
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`FORD 1227
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`Page 21 of 52
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`
`
`portion of heat engine power transmitted mechanically to the rear wheels is
`
`shown by the dashed line and is just equal to that power required for constant
`
`velocity road load demand. The difference,
`
`then, between the selected mini-
`
`mum power level and road-load demand is available to the generator, and is
`
`either used to charge the battery, go to the drive motor during acceleration,
`
`or to an energy dump circuit as appropriate to the particular driving
`
`schedule/cycle. During periods of vehicle deceleration,
`
`the mechanical
`
`power is reduced to zero and the heat engine power output is reduced to
`
`the minimum level. The motor (as a generator) and/or the generator can
`
`then utilize the heat engine power output during vehicle deceleration for
`
`battery recharging.
`
`10.2
`
`SIZING STUDIES
`
`10. 2.1
`
`Subsystem Sizing
`
`In order to conduct the desired performance and tradeoff studies,
`
`it was
`
`necessary to select subsystems, define vehicle characteristics and establish
`
`a baseline for comparing various vehicle classes.
`
`It should be stressed
`
`that,due to the complexity of factors and problems involved in analyzing
`
`various hybrid systems during the short duration of this study,
`
`it was only
`
`possible to make limited, general investigations of the wide range of sub-
`
`systems and alternative schemes possible. This report should therefore
`
`be considered in this context and as establishing the basis for more refined
`
`inves tigations .
`
`Component characteristics for the electrical subsystem are merely initial
`
`selections, based on the limited scope of technology review of Section 6, and
`
`do not at this time represent either optimized systems or preferred
`
`approaches. Rather they are considered to be preliminary selections serving
`
`as a baseline for comparison of various vehicles.
`
`In the case of the family car for example,
`
`to establish a baseline two types of
`
`motor voltage control were considered, namely:
`
`.
`
`.
`
`A solid state chopper control
`
`Voltage step switching combined with field control of the motor
`
`10-16
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`Page 22 of 52
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`
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`Since step voltage switching. combined with field control of the motor has
`
`not been extensively demonstrated for automotive application,
`
`this scheme
`
`would require thorough investigation to determine the feasibility of use in
`
`hybrid powertrains.
`
`If such a scheme is proven to be feasible,
`
`it offers the
`
`advantages of higher efficiency,
`
`lighter weight, and possibly lower cost.
`
`A comparison of component weights for electrical subsystems in series and
`
`parallel powertrain configurations is shown in Tables 10-1 and 10-2 for
`
`each vehicle class. All data shown are based on a control scheme using
`
`step voltage switching combined with field control of the motor except for
`
`the first column in each table which is based on a chopper scheme for
`
`controlling motor voltage. The two types of electrical control systems
`
`have been presented here in the case of the family car solely for relative
`
`comparison of weight, volume, and efficiency. This shows that the dif-
`
`ference in the total Weight of electrical components in the two approaches
`
`is quite small compared to the overall family car weight.
`
`The step voltage/field control scheme was chosen for the final analysis
`
`of component weights, power requirements, and costs, and was used as
`
`the basis for comparing the performance of various classes of vehicles.
`
`it
`
`is felt that the performance data obtained with this scheme applies approxi-
`
`mately to the chopper approach.
`
`10. 2.1.1
`
`Series Configuration
`
`Table 10-1 denotes the characteristics of the electrical subsystems (drive
`
`motor, motor controller, generator, generator controller, AC rectifier)
`
`selected for the baseline series configuration for each of the six vehicle
`
`classes.
`
`Included in the table are such features as subsystem type, rating
`
`(where appropriate), volume, weight, and efficiency at rated load conditions.
`
`As mentioned previously,
`
`the final drive for the series configuration is
`
`defined as a conventional differential drive unit, adapted to contain an over-
`
`drive mechanism for a step-change in gear ratio during high-speed cruise
`
`operation for increased drive motor efficiency. The heat engine, of course,
`
`Page 23 of 52
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`10-17
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`Page 23 of 52
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`Page 25 of 52
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`FORD 1227
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`
`
`can be any one of the five classes under examination in the present study
`
`(i.e., 3.1. engine, diesel, gas turbine, Rankine, Stirling). A small gearbox
`
`(Speeder or reducer) is utilized between the heat engine and generator to
`
`produce the desired speed ratio between these subsystems.
`
`The required batteries,
`
`in terms of power density and energy density, were
`
`not treated in this portion of the study effort except on the basis of power-
`
`plant weight available for battery use. Rather,
`
`the battery requirements
`
`were determined with the use of the computer program and the various driving
`
`cycles for each vehicle (See Section 11).
`
`10. 2. 1, 2
`
`Parallel Configuration
`
`Electrical subsystems with characteristics similar to those of Table 10-1
`
`were also considered to be applicable to the parallel configuration, except
`
`for rated size, weight, and volume changes necessitated by the sizing require-
`
`ments of the parallel mode of operation. Table 10-2 denotes the electrical
`
`subsystem characteristics selected for the baseline parallel configuration.
`
`The same comments as to batteries, control system, generator, heat engine,
`
`Speeder/reducer, and final drive that were made for the series configuration
`
`apply to the parallel configuration.
`
`In addition, a conventional automatic
`
`transmission was assumed in the driveline between the heat engine and the
`
`final drive unit.
`
`10.2.2
`
`Sizing Criteria
`
`10. 2. 2. 1
`
`Series Configuration
`
`The essential sizing criteria and significant operational efficiencies assumed
`
`for the baseline series configuration are shown in Table 10-3.
`
`With regard to electric drive motor sizing,
`
`the family car, commuter