Predicting the mechanical vibration caused by magnetic forces in electric machines is a multidisciplinary subject involving electromagnetic and mechanical models. A recent publication has introduced the vibration cause diagram (VCD) as a new graphical tool capable of reconciling the complexity of these individual models with the predictions of the rotating field theory, which allows the root cause of any vibration harmonic to be identified. This has been successfully applied to synchronous machines, resulting in a holistic diagram that shows the cause-effect relationships between flux density and force density waves.The purpose of this work is to extend the VCD method to induction machines as well, which are used in a wide range of industrial and traction applications. This is achieved by taking into account the rotor’s residual spatial harmonics and applying a transformation of the operating point to achieve a time-efficient calculation. The method is validated by simulations and the results for two example cases are discussed. It turns out that the VCD is potentially useful for the design of new machines and for the troubleshooting of vibration problems in existing machines, allowing the design engineer to effectively address the root causes of observed problems.

This paper describes a relationship investigation and a calculation method for time-efficiently predicting the complex spatial harmonic leakage inductance of doubly fed induction generators (DFIGs) considering parasitic effects, such as spatial harmonics due to slot openings and magnetic saturation effects in the iron core. The dependencies of the complex spatial harmonic leakage inductance on the phase current and magnetizing current are first researched using results determined entirely by magnetostatic finite element method (FEM) calculations at different phase currents and magnetizing currents. The locus curves of the complex spatial harmonic leakage inductance are then approximated using the analyzed relationships and significantly fewer magnetostatic FEM calculations. Finally, a comparison with locus curves determined entirely by magnetostatic FEM calculations validates the proposed relationships.

This paper investigates the sensitivity of commonmode prediction results for electrical machines to the assumed position of hairpins of a stator winding within a slot. The effect of the conductor's position on the parasitic motor capacitance between the winding and the stator core as well as on the high-frequency behavior of the machine, i.e., the commonmode current, is investigated using a stator sample. The limiting cases of the conductor position for maximum and minimum capacitances are presented. Based on the resulting variance of the capacitance and the frequency response, it is deduced whether or not a common estimation approach using a symmetrical conductor position is valid.

Due to the increased voltage stress on the winding of an electrical machine during inverter operation, it is necessary to take this additional stress into account in the design of the insulation system. In this paper, a comparison of the measured and the simulated potential distributions in an inverter-fed hair-pin stator winding is presented. The method used to predict the potential distributions within a winding enables to identify spots with high potential differences. This information of the maximum potential differences can then be used to design the insulation system of the electrical machine. Using the measurement of the potential distribution of a sample stator specimen with a hairpin winding, the predictive method is validated. With the help of the validation, it is also possible to demonstrate the accuracy and the limitations of the prediction method.

Hairpin windings are widely used in state-of-the-art traction motors in electric vehicles. The main advantages over traditional round wire windings are the high copper fill factor and thus lower losses and thermal resistance, the short winding head, and a highly automatable manufacturing process. Hairpin windings offer an additional degree of freedom in connecting the conductors of the stator winding in the winding head, which can be used to improve the motor's electrical performance, such as being more resilient to the formation of circulating branch currents. However, due to the high complexity, evaluating every single possible winding configuration often exceeds the computational limits of today's computer hardware. This paper presents a fast and efficient new method to determine viable winding configurations using a new definition to describe the winding and an algorithm that utilizes termination criteria to quickly filter through all possible configurations. Its high modularity enables the developed software to be applied to any electric machine and allows for easy extension.

In this paper, a time-efficient approach to predict vibrations on the stator of electrical machines is extended to predict vibrations on the generator rotor of a wind turbine. Nodal and lumped force methods to projecting forces on the mechanical structure are discussed and compared with pure FEA solution. Furthermore, node reduction technique is employed at the rotor side to reduce computational efforts. Finally, predicted vibrations are compared with experimental results.

This paper deals with the transmission of the field current in electrically excited synchronous machines (ESM) using brushes and slip rings. First, the theoretical principles related to brushes and sliding electrical contacts are presented. It is described how brush dynamics can lead to partial or complete lift-off of the brushes. We explain the possibility of predicting electric arcs arising when the brush is lifted and evaluate the usability of the developed models. Next, measurement results on brush slip-ring systems are presented and discussed. Finally, simulations using finite element method (FEM) are used to investigate the effects of brush dynamics on torque and iron losses in an ESM.

This paper presents a novel approach for reducing the computation time for the determination of the characteristics of PM synchronous machines. The proposed method makes use of the a priori knowledge of the spatial harmonic spectrum of the air-gap field, which determines the harmonic spectrum of parameters like flux linkages, inductances or torque. When the harmonics with the most influence on the operating behaviour are known, systems of equations can be formulated and only a rather small number of magnetostatic FEM calculations needs to be performed to solve the systems. Hence, the calculation time for a simulation can be lowered drastically without a loss in accuracy.

Eddy-current losses in permanent magnets of a surface-mounted permanent-magnet synchronous machine (SPMSM) are analytically calculated by solving magnetostatic and magnetodynamic field problems. The magnetostatic solution neglects the eddy-current reaction fields and depicts a large deviation compared to a Finite Element Analysis (FEA). A correction factor introduced into the magnetostatic calculation does not provide sufficient accuracy at high frequencies. The magnetodynamic calculation, which takes the eddy-current reaction fields into account, achieves a good agreement with a Finite Element Analysis.

The growing complexity of todays technical systems demands for improved simulation techniques. One important aspect is the way how hierarchy of interconnected dynamical systems is handled. Focusing on this, some existing approaches are reviewed and a modified component connection modeling (CCM) framework is introduced. Furthermore, several conceptual considerations of CoSimMA, a modular simulator based on this theoretical foundation, are presented. As an example, the hierarchical modeling of a wind turbine and the included power electronics is outlined.