Since the early 1900's demand for fuel efficient vehicles has motivated the development of electric and hybrid electric vehicles. Unfortunately, some components used in these vehicles are expensive and complex. AC motors, complex electronic controllers and complex battery management systems are currently used in electric (EV) and hybrid vehicles. This research examines various motors and speed control methods in an attempt to help designers identify which motors would be best suited for an EV powertrain application. The feasibility of using DC motors coupled with an Infinitely Variable Transmission (IVT), to obtain an innovative new electric or hybrid electric powertrain is also presented. The results of this research include an extensive review of the many motor types including a comparison chart and motor hierarchy. An experiment was designed and built to test motorspeed control methods. Testing with two DC separately-excited motors and a differential as an IVT was also conducted. These tests revealed that field weakening appears to be a viable low-costspeed-control method. Testing of these motors, coupled with an IVT revealed that the output of a differential or planetary gear set can be controlled by varying the speed of the inputs. Combining this information in a product development mentality led to the concept of using one DC motor as a power or traction motor while another motor acts as a speed controller, with the method of speedcontrol on the speed control motor being field weakening. This concept allows most of the power to be delivered at an efficient rate with a simple form of speed control. This concept may also eliminate the need for expensive, complex electronic motor controllers. This approach could be used to improve the safety and reduce battery management requirements by lowering the operating voltage of the entire system.

Since the early 1900's demand for fuel efficient vehicles has motivated the development of electric and hybrid electric vehicles. Unfortunately, some components used in these vehicles are expensive and complex. Today's consumer electric vehicles use dangerously high voltage,expensive electronic controllers, complex battery management systems and AC motors. The goal of this research at BYU is to increase safety by lowering the operating voltage and decrease cost by eliminating expensive controllers and decrease the number of battery cells. This paper specifically examines the use of a Ward Leonard Motor Control system for use in a passenger vehicle. The theory of the Ward Leonard system as an Infinitely Variable Transmission (IVT) is presented along with its history and past uses. Analogous systems are presented and similarities made in an attempt to enlighten designers to a broader design approach to increase safety and decrease cost of an electric or hybrid electric vehicle. The results of this research include a characterization of the Ward Leonard system as an IVT for use in an electric or hybrid (EV or HEV) passenger vehicle. These results include a study of past uses of the Ward Leonard system and what method is now used as a replacement. The theory of the Ward Leonard system and it operation is explained to an extent that someone not familiar with electronics can understand its working principles. A Control Factor metric was developed as a result of this research to measure the Ward Leonard System's ability to reduce the size of the electronic controller for application in an EV or HEV. The potential cost reduction of the electronic controller that would be used to control the Ward Leonard System compared with current EV and HEV vehicles was also research and identified. A bench top model of the Ward Leonard system was tested validating the Control Factor metric. The Ward Leonard system is capable of reducing the controller size by 77% and potentially reducing its cost by 68% or more. This work also provides performance characteristics for automotive designers and offers several design alternatives for EV and HEV architectures allowing the reduction of high voltage, the use of AC inverters, AC motors, expensive controllers and high cell count battery packs.