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.



College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering



Date Submitted


Document Type





Cody Telford, electric vehicle, Ward Leonard, motor testing, CVT, IVT, low cost, DC, LabView, shunt wound, DC motor, hybrid, variable voltage, control factor