Advanced electronic control systems for electric vehicles
The characteristics and relative advantages of several types of electric vehicle control systems are discussed. An advanced electronic control system for a separately excited dc motor is described. Performance characteristics of an electric vehicle using this control are discussed and recommendations for future systems are given.
Comparison of electrical drives for road vehicles
The low storage capacity of presently available galvanic batteries restricts the effective use of electrically driven vehicles to a limited range of transportation jobs. For this application any change from vehicles driven by internal combustion engines to vehicles driven by electric motors can only be justified if the use of electrical drives results in an overall cost reduction. This criterion means that a direct current, separately excited motor with its speed controlled by field weakening is the best solution. In a conventionally designed motor the attainable speed range is limited to approximately 1:3. In most cases additional means for the extension of the driving range are required. If, however, the motor is equipped with an additional compensation winding, a controllable speed range of close to 1:8 is obtainable by field weakening. Acceleration characteristics are applied to evaluate the various drive units which provide advantages in energy consumption and disadvantages in the acceleration time, and vice versa. On the basis of test vehicles with various drive systems, design of the required control is explained. Additional requirements for automatic control are partially offset by the additional protective devices required to restrict the effects of faulty handling of a manually controlled drive.
Propulsion systems for electric cars
Proper selection of the propulsion system to meet the requirements of an electric passenger vehicle is of prime importance. Choice may be made among alternating current, direct current, or combined systems. Each approach can be implemented by utilizing various control techniques and power elements. For instance, an ac system may use an adjustable voltage inverter (AVI) or a pulse-width-modulated inverter (PWMI) for the power processor, and an induction motor or a synchronous motor for the rotating element. Similar alternatives exist for a dc system. The choice of a suitable manner of implementation must be. based on information characterizing the various elements and tradeoffs matching them to the vehicle requirements. This paper describes various ac and dc techniques, characterizes AVI, PWM, and representative dc chopper power processors and examines their interface with a variety of motors such as series, shunt, induction, etc.