An approach to propulsion subsystem technology is presented. Various tests of component reliability are described to aid in the production of better quality vehicles. component characterization work is described to provide engineering data to manufacturers on component performance and on important component propulsion system interactions

Schwartz, H. J.

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Propulsion System Research and Development
for Electric and Hybrid Vehicles
HarveyJ. Schwartz
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio
The NASA Lewis Research Center is responsible for planning and implementing all propulsion
system research and development work being supported under the Department of Energy's Electric
and Hybrid Vehicle program. During the past 3 years the propulsion system project has grown until it
now involves participation by approximately 30 industrial firms and universities through contracts
and grants totaling over $7 million.
Present-day propulsion components and systems are unsuitable for a mass-produced consumer
electric vehicle for two reasons. One is that available components are not designed for road service.
As a result they are heavy and expensive and have relatively low efficiencies. In many cases basic
performance data taken under conditions that are encountered in electric vehicle service are not
available. The second reason is that the market for electric vehicles is not large enough, nor does it
appear to be near-term enough, for manufacturers to invest funds in developing custom-built
components for electric vehicles., Not only do the component manufacturers lack incentive to
produce new products on their own, but the electric vehicle manufacturers do not have enough
leverage with their suppliers to get the necessary technology development done. Therefore propulsion
component and system technology development must be Government-supported for at least the near
future in order to stimulate electric and hybrid vehicle commercialization.
The Lewis Research Center's approach to propulsion subsystem technology is as follows: For the
next few years we will be providing engineering information to manufacturers that will assist them in
building better electric vehicles. This will be done primarily through testing components now avail-
able to manufacturers and publishing data on their performance and through developing a
component catalog that will give manufacturers a source of information on where to obtain
propulsion components for their vehicles. Technology development in the near term will involve the
development of improved components and propulsion subsystems based on existing technology. The
philosophy here is to adapt the best existing techniques and designs to produce components
specifically for electric and hybrid vehicle use. In the long term, advanced components and systems
will be based on totally new technologies and will be quite different from those on the market today.
The emphasis in all the development work is on cost, weight, and efficiency, with cost being the
primary factor at present. This is because our studies show that if large-scale production of an electric
vehicle were to take place using existing propulsion technology, as much as 50 percent of the cost of
the vehicle to the consumer would be associated with the propulsion system. Therefore propulsion
R&D offers a great opportunity for reducing the cost of electric and hybrid vehicles.
Component Characterization
Component characterization work is designed to provide engineering data to manufacturers on
component performance and on important component-propulsion system interactions. Work is
under way on motor and controller testing, transmission testing, and the study of battery-propulsion
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https://ntrs.nasa.gov/search.jsp?R=19810004474 2020-03-21T14:41:15+00:00Z
system interactions (fig. 1). The Eaton Corp. is the major contractor for motor, controller, and
transmission testing and TRW, Inc., is conducting a battery testing project. Examples of the results
of this work are shown in figures 2 and 3.
In figure 2 the efficiency in percent is plotted against the output in kilowatts for an electric vehicle
traction motor operated in two different manners. The upper curve shows its performance on ripple-
free dc electricity; the lower curve shows the way the motor performs when it is coupled with a
conventional chopper type of dc motor controller. The ripple-free dc characteristic curve is typical of
what an electric vehicle manufacturer obtained from a motor supplier's catalog; the chopped dc
curve represents how the motor actually operates with a typical speed controller that would be used in
a vehicle. Notice that in some areas, particularly at low power outputs, the difference between the
two curves can be as much as 10 percentage points. This difference in efficiency results in a direct
reduction of the range of the vehicle.
Figure 3 shows the performance of a three-speed automatic transmission from a compact car. Here
the efficiency is plotted against the output speed under a range of conditions that are typical of what
the transmission would see if it were operating in an electric vehicle. In an ordinary passenger car this
transmission would have an efficiency approaching 90 percent, but in an electric vehicle it is
operating sufficiently far from its optimum design point that the efficiency reaches a maximum of
only about 80 percent. Again this results in a significant drop in range. Thus it is clearly important
for the vehicle manufacturers to have performance data of this type. Unfortunately, this kind of data
is not normally available from the component suppliers, and the vehicle manufacturer usually does
not have the resources to provide it for himself.
COMPONENT CHARAC TE:RtZAT1 ON
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Figure 1
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EFFECTOFCHOPPEDCONMOTOREFFICIENCY
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Figure 2
3 SPEEDAUTOMATICTRANSMISSIONTESTDATA
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Figure 3
Component Development
The NASA Lewistechnology developmentprogram is focused on three separate areas: One is
power conditioning, which relates to the development of motor controllers. The second is the
development of new traction motors of various types. The third involves transmissions designed
specifically for electric and hybrid vehicles. Our long-term goal is to provide a propulsion system that
has an efficiency approaching 80 percent under urban driving conditions and that will cost
approximately $80 per kilowatt of rated power output and weigh about 7 kilograms per rated
kilowatt. If we can reach these goals, the long-term effect would be a 20- to 30-percent reduction in
the sticker price of an electric car and a 15- to 20-percent reduction in the overall life-cycle cost of that
car to its owner.
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Examples of our work on traction motor development are shown in figure 4. The improved motors
that are being developed by AiResearch Manufacturing Co. and Virginia Polytechnic Institute use
existing technology and are rather conventional in appearance and design. The advanced motors
shown in the lower part of the figure are radically different. They emphasize the use of low-cost
materials and novel design approaches that can result in smaller, lighter, and cheaper motors. The
contractors for our advanced motor work are the General Electric Co., Westinghouse, and the
Garrett Corporation's AiResearch Manufacturing Co. Other propulsion components presently under
development are shown in figure 5. Motor controllers are being developed by the Chrysler Corp.,
General Electric, and Gould. The left photograph in the upper part of the figure shows a high-
frequency (10-kHz) chopper type of controller that has been built and tested by Chrysler. It has an
efficiency in excess of 90 percent over most of its operating range. The high frequency has a side
benefit in that it tends to eliminate the characteristic unpleasant whine associated with the lower
frequency choppers now used in controllers for electric vehicle motors. The right photograph shows a
"breadboard" version of a motor controller being developed by General Electric that uses a new,
lost-cost power transistor also under development at GE.
Continuously variable transmissions could be of great value not only to electric vehicles but to
conventional automobiles as well, since they provide a way of improving the match between the
motor output and the road load. Several promising designs are being investigated for electric and
hybrid vehicle use, but it will be a number of years before they are available for installation in
vehicles because of the difficult engineering problems that must be solved.
Propulsion System Development
NASA Lewis is also supporting the development of complete propulsion systems, for example, the
ac drive being developed for Lewis by the Eaton Corp. (fig. 6). It consists of two major parts: One is
NEW PROPULSION COMPONENTS
TRACTIONMOTORS
Figure 4
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...... 2 _
Figure 5
the ac motor, its controller, and a microprocessor or computer that controls the motor. The other is a
two-speed, geared, automatic transaxle. The advantages of ac drives are well known. The motors are
small and lightweight, require little maintenance, and lend themselves to mass production at low cost.
The main disadvantage to an ac drive at present is the cost of the power transistors required for the
inverter that controls the motor. The transaxle has been tested and has an efficiency of greater than
90 percent. An attractive feature of the transaxle is that it can also be used with a dc drive if it turns
out that the transistor cost reductions do not come about as rapidly as they are expected to. The lower
sketch in figure 6 shows an artist's conception of how the system would look if installed in a
subcompact car of the Ford Fiesta size.
Propulsion system testing is expensive and difficult if it is done in a complete vehicle. This summer
the Lewis Research Center will dedicate a new facility called the Road Load Simulator Facility. This
unique laboratory is designed for testing electric and hybrid vehicle propulsion systems over a wide
range of driving conditions in a variety of simulated vehicles at low cost and with high accuracy and
reproducibility. We will be able to test propulsion subsystems under the conditions they would see in
many kinds of vehicles, ranging from small subcompact cars to large delivery vans. A programmable
driving-schedule controller will allow us to reproduce almost any type of traffic condition. The result
will be accurate, convenient, cost-effective testing of electric and hybrid propulsion systems. The first
system to be tested is shown in the lower right of the figure. It is the propulsion subsystem from the
General Electric-Chrysler ETV-1 electric vehicle, which was developed for the Department of
Energy and is described in the paper by Thomas Barber of the Jet Propulsion Laboratory.
In summary, the NASA Lewis Research Center expects four major benefits to accrue from our
propulsion system R&D work. First, we will provide current vehicle manufacturers with engineering
design data and new propulsion components and systems that will assist them in producing better
vehicles. Second, we will improve the technology base from which vehicle manufacturers can draw in
the future in designing commercial vehicles. Third, we expect to help reduce the near-term R&D
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Figure 6
investment required by industry while the potential market is uncertain. And finally, we expect to
significantly reduce the purchase price and ownership cost of mass-produced electric and hybrid
vehicles.
Since we are dealing in research and development work that is associated fairly closely with a
potential commercial product and are attempting to stimulate an earlier commercialization of that
product, we believe that new approaches are going to be required in our R&D contracts. We feel that
it will be necessary to provide incentives to industry in the form of cost and risk sharing at times when
market conditions make R&D investment by industry on their own unlikely. These incentives might
take the form of exclusivity in data and patent rights in return for which we would expect industry to
pay back the Government's investment if the projects are successful. This is something that is already
being done in our aeronautics program. Furthermore we will have to protect the taxpayers' interests
by insisting on "march in" rights to have others continue the work if the company decides to drop
the project and a market still appears to exist. We are presently discussing an approach to this type of
procurement activity with the Department of Energy for possible use in future procurements.
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Concluding Remarks
The electric vehicle was once a major factor in our Nation's transportation system. Today we are
seeing rebirth of the electric vehicle industry based on conversions of conventional automobiles and
light trucks and a few purpose-built electric vehicles with somewhat limited performance. By the
mid-1980's, however, we expect this industry to grow to the point where mass-produced, carefully
engineered electric vehicles with high consumer appeal are going to begin to appear on the roads.
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Propulsion system research and development for electric and hybrid vehicles

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