Electromotive power and locomotion

The total cost of the vehicle electrical propulsion systems and the wayside power supply system is a significant proportion of the cost of a transit system. This paper addresses the problem of selecting propulsion systems for transit vehicles. It is shown that the power characteristics of the motor have a major influence on effective utilization of the power capacity and that increasing the power level brings diminishing returns in schedule speed. Generalized performance curves are developed which can be used in comparing the effect of using various power levels and motor characteristics. An example is used to demonstrate the significant benefits of motors which provide a constant horsepower in the field-weakening speed range.