Kuhl, D., Brabetz, L., and Ayeb, M., "A New Approach to Calorimetric Efficiency Measurements and Analysis of Electric Vehicle Drive Losses," SAE Int. J. Alt. Power. 5(1):115-121, 2016, doi:10.4271/2016-01-1168.
The development of battery electric vehicle drives comes along with comprehensive and time-consuming finite element methods and extensive measurement campaigns. The drive efficiency has drawn great attention from engineers and customers, because it influences the size of the drive, the cooling measures and the vehicle range.Indirect efficiency acquisition accomplished by comparing inward and outward power, has a low accuracy which arises from a relatively small difference between inward and outward power of highly efficient drives. Therefore the indirect efficiency acquisition is insufficient to evaluate advanced development measures. This paper presents measurement and analysis methods developed within a collaborative research project, which aims at accelerating the development cycles of electrical drives by implementing and combining accuracy-improved Finite Element Simulations (FEM), extremely rapid Lumped Parameter Thermal Networks (LPTN) and a new efficiency measurement method with high accuracy. Findings of this project provide possibilities to optimize drive construction, material selection and control strategy.The new approach of efficiency measurements is based on a direct loss measurement. Moreover, this approach adopts an innovative calorimetric measurement principle with the support of conventional dynamic measurement procedures: The calorimetric measurement principle yields to a high steady-state-accuracy; the conventional measurement identifies dynamic transitions.This paper not only introduces highly precise measurement methods for evaluating heat dissipation of electric drives, but also new evaluation methods for the determination of internal power losses. An evaluation of test bench measurements is shown, in order to demonstrate the process of distinguishing different losses.