Investigation of thermal energy losses in the powertrain of an electric city bus

This paper evaluates thermal losses and thermal energy transfer in the powertrain components of an electric city bus. A simulation model of an electric city bus was developed in AMESim simulation software. Simulations were carried out in four different driving cycles and in different ambient temperatures. The simulation results show that there is a strong correlation between thermal losses of the inverter and electric motor with the total energy losses. Based on the results, thermal energy transfer from the components to the coolant was analyzed. The thermal energy transfer from the battery to coolant was higher in more demanding driving cycles whereas aggressive driving has more impact on the thermal energy transfer of the inverter and electric motor. In cold ambient temperature, auxiliary power losses increase significantly due to the need of heating. Battery losses are also higher in cold conditions because of the higher internal resistance.