Calculation of the Losses of Series-Hybrid Powertrains

Regarding mobile machinery, particularly agricultural tractors, there is an ongoing competition for the most suitable technology to achieve optimum functionality with maximum efficiency. In this competition, the efficiency of electric series-hybrid powertrains (ESHPs) is often depicted as worse than the efficiency of mechanical-hydraulic power-split powertrains (MHPSPs). On closer inspection of these statements, however, systematic errors, such as unequal balance limits, neglected size effects and nonlinearities, non-observance of recent technical developments and standards, or erroneous application of research results regarding MHPSPs on ESHPs are often evident. For verification (and under avoidance of the systematic errors mentioned above), the losses of an ESHP of 150 kW power are for example calculated and compared with the losses of a typical MHPSP of the same power. The comparison of the losses shows that the ESHP clearly exceeds the efficiency of the comparative MHPSP in the main working range and that there is still potential for improvement.