Energy Consumption Calculation of an Electric Bus with a Variable or Fixed Gearbox

This paper presents a methodology for energy consumption calculation and drive train optimization for an electric bus. The mechanical, motor and inverter models are described. The methodology allows to calculate the efficiency maps and the energy consumption in kW/km. A 14t bus with motor power ranging from 92 to 122 kW is used. A fixed or a variable gearbox is considered. The calculations are based on measured data from real bus lines on various terrain in the city of Prague. The calculation is then compared to the measured energy consumption on a similar terrain, yielding a 7% difference between the calculated and measured energy. The calculation shows, that a variable gearbox could save few percent of energy. The differences in energy consumption between the fixed and variable gearbox are in the order of few percent. The disadvantages are increased cost, maintenance, decreased reliability.