Hybrid-electric transit buses are now entering the transit bus marketplace. These electric vehicles allow the ICE (internal combustion engine) to be optimally tuned to maximize efficiency and reduce emissions while traction batteries provide the capability to capture braking energy. New York City has recently placed a second order for hybrid-electric transit buses with the combined number now on order at 325. Fuel Cell technology is rapidly advancing which could accelerate the demand for electric drive systems. Transit buses typically draw from the trucking industry for major components such as ICEs, axles, and transmissions. The preponderance of these vehicles are 40-foot buses with a maximum Gross Vehicle Weight of 39,500 pounds. Inner city bus routes entail low speed with numerous starts and stops. While bus weight and route profile dictate overall torque and power requirements, many other factors constrain the electric drive configuration. Determination of torque and power must take into account gearbox and axle ratios, component efficiencies, motor speed, and respective losses in the drive train. The traction motor must be bidirectional to recover or dissipate braking energy. The bus voltage may be established by the current limits on the switching electronics in the power management subsystem. Finally, adequate heat rejection must be provided. This paper addresses the issues impacting transit bus electric traction drives and describes some of the systems currently in use.
Electric traction drives for heavy urban transit buses
Elektrische Antriebe für große ÖPNV-Busse
2001
10 Seiten, 15 Bilder, 1 Tabelle, 4 Quellen
Conference paper
English
Hybrid Electric Drives for Heavy Duty Transit Buses
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