In order to achieve the European Commission’s ambitious climate targets by 2030, BEVs (Battery Electric Vehicles) manufacturers are faced with the challenge of producing more efficient and ecological products. The electromechanical powertrain plays a key role in the efficiency of BEVs, which is why the design parameters in the development phase of electromechanical powertrains must be chosen carefully. One of the central design parameters is the maximum speed of the electric machines and the gear ratio of the connected transmissions. Due to the relationship between speed and torque, it is possible to design more compact and lighter electric machines by increasing the speed at constant power. However, with higher speed of the electric machines, a higher gear ratio is required, which results in a larger and heavier transmission. This study therefore examines the influence of maximum speed on the power density of electromechanical powertrains. Electric machines and transmissions with different maximum speeds are designed with the state-of-the-art for a selected reference vehicle. The designs are then examined with regard to the power density of the overall powertrain system. Compared to the reference vehicle, the results of the study show a considerable potential for increasing the power density of electromechanical powertrains by increasing the maximum speed of the electric machines.

This article provides an applicable method to predict the distribution of the electric potential inside the winding of an electrical machine with a reasonable set of parameters. It extends the understanding of the winding impedance in terms of the inter-winding behavior and gives us the opportunity to properly design the insulation system during the development phase of an electrical machine. Predictions are backed up by measurements and an in-depth look at the measurement setup. The results proof nonuniform potential distribution and show that the potential difference between individual turns exceeds the amplitude of the phase voltage. Our findings also establish an interrelation between the winding impedance and the potential oscillations inside the winding. The article provides an introduction to the fundamental process of voltage stress on electrical machine windings and discusses drivers for upcoming challenges in the field of winding insulation and partial discharges.

This paper presents parametric models for high-frequency common- and differential-mode impedance analysis of electrical machines. The models are presented in terms of lumped equivalent circuit diagrams and their corresponding complex impedance equations. In order to parameterize the models, the differential evolution algorithm is used and a minimisation problem is defined. For model validation, the complex model impedance is compared to the measured impedance of eleven electrical machines of the same type. Furthermore, the lumped equivalent circuit parameters are individually identified for every single electrical machine and the resulting data is statistically interpreted. Moreover, detailed geometry and stator winding data as well as insulation material data of the investigated electrical machine are given. The intention is to enable more accurate simulations for EMC and insulation stress investigations as well as for filter and inverter designs.

The accurate analytical calculation of iron losses in electrical machines is still a great challenge for designers of electrical machines. There are a lot of different analytical approaches applying in order to reach good results. Comparisons between the analytical approaches and measurements of the specific iron losses of unmachined electrical sheets show that the loss coefficients of the approaches strongly depend on the operating range of the magnetic flux densities and frequencies. In order to keep the discrepancy between measurement and approaches depressed it is reasonable to calculate the loss coefficients depending on its application. In this paper several calculation methods are discussed and the loss coefficients are determined for particular application cases. As a result the error of calculation and measurement can be kept small. Obviously discrepancies due to the different process steps during the manufacturing process have to be considered by correction factors as well.

This article describes a practical method for predicting the distribution of electric potential inside an electrical machine’s winding based on design data. It broadens the understanding of winding impedance in terms of inter-winding behavior and allows to properly design an electrical machine’s insulation system during the development phase. The predictions are made based on an frequency-dependent equivalent circuit of the electrical machine which is validated by measurements in the time domain and the frequency domain. Element parameters for the equivalent circuit are derived from two-dimensional field simulations. The results demonstrate a non-uniform potential distribution and demonstrate that the potential difference between individual turns and between turns and the stator core exceeds the expected values. The findings also show a link between winding impedance and potential oscillations inside the winding. Additionally, the article provides an overview of the chronological progression of turn-based models and shows how asynchronous multiprocessing is used to accelerate the solution process of the equivalent circuit.