The additional weight in Electrovan beside the powertrain, was caused partly by body and structure changes and partly by experimental equipment. Most of the instruments, meters, monitoring and safety systems would not be required in a fully developed vehicle. With development, at least 1000 to 1500 pounds could probably be removed from Electrovan without using any new technology. However, this would still leave the vehicle 70% heavier than its gasoline engine counterpart. One of our most significant findings was that the fuel cell auxiliary system weighs almost as much as the fuel cell modules and electrolyte. Maximum power tests of Electrovan were not run on the road because of several system limitations. However, the motor and control system, and the fuel cell powerplant have each been tested separately as shown in Figures 14 and 18. On the basis of these tests, a 0 to 60 mph acceleration time of 30 seconds and a top speed of 70 mph were considered realistic estimates. These compare favorably with data for the production van as shown in Table 3. Data from road operations indicated that the Electrovan consumed, on the average, about 1 kw-hour of energy per mile. Therefore, the van could be driven about 120 miles on the 12 pounds of liquid hydrogen stored in the cryogenic tank. REFERENCES 1. "The Hydrogen-Oxygen Thin Electrode Fuel Cell Module", C. E. Winters, and W. L. Morgan, SAE Paper No. 670182, Jan. 1967. 2. "A Vehicle Fuel Cell System", F. A. Wyczalek, D. L. Frank, and G. E. Smith, SAE Paper No. 670181, Jan. 1967. 3. "A High Performance AC Electric Drive System", P. D. Agarwal, and I. M. Levy, SAE Paper No. 670178, Jan. 1967. 4. "Electrovair II - A Battery Electric Car", E. A. Rishavy, W. D. Bond, and T. A. Zechin, SAE Paper No. 670175, Jan. 1967. The recent advance in power handling capacity of semiconductor devices makes it possible to replace DC and AC commutator machines for variable speed applications by high-speed, light-weight, squirrel-cage induction motors. This paper describes the development of a high-performance electric drive system which uses squirrel-cage induction motors in which slip frequency is externally controlled. This makes it suitable for traction applications. Two systems were specifically built for installation in a battery-powered automobile and a fuel-cell powered delivery truck. The performance of these vehicles has proven the technical feasibility of an electric powered vehicle. A HIGH PERFORMANCE AC ELECTRIC DRIVE SYSTEM INTRODUCTION The two major components for powering an electric automobile are the electrical power source and the drive motor and control system. Although the size, weight, and cost of presently available fuel cells or batteries have prevented their use in commercial passenger cars today, extensive research and development throughout the world may make such a power source available in the future. The research and development of high-performance AC variable - speed drive systems at GM Research Laboratories (Santa Barbara, California) and at Delco Products (Dayton, Ohio) for various applications contributed importantly to undertaking the building of experimental electric vehicles. The guidelines for such a development included the following: 1. The performance of the electric vehicles must equal or exceed that of an equivalent modern automobile with the internal combustion engine. powered from a constant frequency source, the conventional squirrel-cage induction motor operates at essentially constant speed (Figure 1). Variable speed operation of these motors can be obtained efficiently only by varying the frequency of the voltage source, and this, until recently, has required a variable speed alternator. The advent of the thyristor (silicon controlled rectifier SCR) and its availability in high power ratings have made possible the development of static frequency converters and inverters which are compact, reliable and efficient, and thus provide the requisite variable frequency power source for variable speed operation. TORQUE FULL LOAD TORQUE NORMAL OPERATING RANGE |