San Francisco MUNI trolleybus propulsion tests: The results

The San Francisco Municipal Railway (MUNI) fleet of 345 trolleybuses, the largest in North America, is powered by dc motors with switched resistor controllers. Under an Urban Mass Transportation Administration (UMTA) grant, MUNI conducted a Trolleybus Propulsion Evaluation Program, in which the energy use and performance were measured of the existing switched resistor dc motor controller and three chopper and ac propulsion systems. For each of the systems, tests were conducted on level, medium, and hilly routes, with empty, seated, and crush loads. Graphical analyses are presented, comparing net propulsion energy, regenerated energy, control losses, net motor energy, and rheostatic braking losses for the four systems. Advanced systems are shown to reduce propulsion energy use by an aggregate average of 39 percent compared to the switched resistor controller.