High-speed electric machines are gaining importance in the field of traction drives and aviation due to their high power density. The evaluation of the mechanical stress in the rotor is one crucial part in the design process for this type of machines. The mechanical stress cannot be measured directly. Accordingly, a validation of the calculated mechanical stress is difficult and normally not performed. Instead of the mechanical stress, the deformation at the rotor surface can be measured using a spin test machine with distance sensors. The deformation can then be used to validate the calculation results.In this paper, the mechanical load exerted on an IM rotor for a $60\,\text{kW}/20000\,\frac{1}{\text{min}}$60kW/200001min high-speed electric machine and an PMSM rotor for a $75~\text{kW}/25000\,\frac{1}{\text{min}}$75kW/250001min high-speed electric machine is analysed in detail. The mechanical stress and the deformation are calculated and analysed using a FEM simulation model. Then, a spin test is performed on the two rotors. First, the burst speed is determined by operating two rotor samples above their defined test speed. Then, the deformation is measured at the rotor surface for different operating speeds and the defined test speed. The measurement and the simulation results are compared and discussed.It can be shown that the two designs do not exceed the maximum mechanical stress for the defined operating range. In the deformation measurement of the IM rotor, a plastic deformation up to $\varepsilon _{\text{IM, pl}} = 8$εIM, pl=8 μm and elastic deformation up to $\varepsilon _{\text{IM, el}}=22$εIM, el=22 μm can be seen. In regards to plastics, PMSM rotor expands up to $\varepsilon _{\text{PMSM, pl}}= 5$εPMSM, pl=5 μm. The maximum elastic deformation of the PMSM rotor is $\varepsilon _{\text{PMSM, el}}=40$εPMSM, el=40 μm. The comparison of the calculated and the measured elastic deformation shows good accordance for the two rotor types. Both models are capable of describing the deformation and the state of stress in the rotors. In burst tests, both rotors withstand rotational speeds far above the defined test speed.

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.

High-speed electric machines are gaining importance due to their high power density. The evaluation of the mechanical stress in the rotor is a crucial part of the design process for this type of machines. It is insufficient to evaluate just the static mechanical stress at maximum speed. The dynamic mechanical stress between the state of standstill and maximum speed needs to be considered as well to ensure the high fatigue strength of the rotor. One criterion that is commonly used to analyze the dynamic load in a material is the Smith diagram. In this work, a new methodology is introduced to consider both, the dynamic and the static mechanical stress, in the rotor of a high-speed electric machine. First, the von Mises stress criterion is used to examine the static mechanical stress in the rotor core. Second, the Smith diagram is used to evaluate the dynamic mechanical stress and the high fatigue resistant of the rotor. The methodology is, then, applied to a high-speed electric machine with two different types of buried magnets: 1) a rotor with buried magnets in v-shape and 2) a rotor with a buried bar magnet. Both rotors are analyzed concerning their state of stress. It can be seen that high dynamic stress occurs at the bridges in the rotor. The stress alternates with an amplitude up to σ _alt = 290 MPa. The designs are though limited due to the high static stress at the bridges of the magnet slot.

The vibration and acoustic behavior of electric machines is an important criterion in the design phase. The impact of the winding and the insulation on the eigenfrequencies, the eigenmodes and the damping of the stator is one of the main uncertainties. Therefore, in this work, the influence of a hairpin winding, insulated with two different insulation types, is analyzed. Four different stator specimens are examined by performing an experimental modal analysis and a FE harmonic analysis. On the basis of the results, equivalent material parameters for the homogenized winding, consisting of copper conductors and insulation material, are derived by comparing the simulation and the measurement results. The Young 's modulus (also called the elastic modulus) is identified by performing a parameter fitting. A methodology for comparing and evaluating the measurement and the simulation results is presented. The resulting equivalent material parameters of the winding can be used for future calculations.

The stator core vibration caused by electromagnetic forces is an important topic in the design of electric machines. A crucial task for the comprehensive analysis of this issue is to accurately estimate the eigenmodes and eigenfrequencies of the mechanical system, which allows the calculation of the forced mechanical response. This paper presents a new analytical model based on beam elements as an alternative to the typical finite-element (FE) and classical analytical models applied for this purpose assuming a 2D simplification of the system. The proposed model takes the stator yoke and teeth into account and is able to predict the eigenmodes, eigenfrequencies and forced response of the stator core of rotating electric machines, such as synchronous and induction motors. The results are compared to FE and analytical calculations and validated based on measurements on the stator core of a permanent magnet synchronous motor.