Ralf Kobler

Measurement of the magnetic characteristics of soft magnetic materials with the use of an iterative learning control algorithm

The quality of finite elements simulations is depending on the used magnetic characteristic curves and material coefficients on a high degree. Especially in the automotive industry the power density of electric machines are tending to increase. Thereby the quality of a whole design optimization process for highly saturated magnetic circuits is depending on the accuracy of the material data. To measure the magnetic characteristics of materials at high field strengths and high frequencies, the losses in the coil and the material has to be reduced because of thermal influences. On the one hand the influence of the heating itself is unwanted and on the other hand, especially when small test specimen are used, the maximum measuring time is limited to the temperature and sometimes leads to bad control accuracies. To overcome this problem an iterative measurement cycle is introduced in this paper.

Development of a compact and low cost axial flux machine using soft magnetic composite and hard ferrite

Especially for automotive applications, the request for small, lightweight, powerful and cheap electrical machines is tremendous - not only for the drivetrain in electrical vehicles but also for ancillary components like air conditioning compressors, starters/generators or pumps. In terms of small size and high power to weight ratio, the use of permanent magnets, especially rare earth magnets is essential. However, rare earth permanent magnets(PMs) have several concerns caused by a very concentrated resource market, which has already caused unpredictable price increase or export restrictions. Therefore, it is the goal to avoid rare earth magnets on the one hand but, on the other hand, keep the characteristics of a machine for the automotive industry. The combination of hard-ferrite magnets and soft magnetic composites, combined in an axial flux motor topology is a promising approach to fulfill the requirements of a high power density, low-cost and rare earth magnet-free machine. The designed motor structure with ferrite PMs replacing the rare earth PMs and the results of three-dimensional finite element analyses are introduced in detail in this paper. Moreover, a prototype with 600W nominal output power was produced and tested.

Modeling, simulation and design of a claw pole machine using soft magnetic composites

Using soft magnetic composites (SMC) allows the construction of motor geometries with reduced complexity and high power density. In the automotive industry, these properties become more and more important. Regarding the suitability of SMC for electric machines, the claw pole motor turns out to be highly promising. This paper deals with the analysis and optimization of such a claw pole geometry. The initial design dimensions are achieved with the help of an analytic design parameter model. Furthermore, the details of the magnetic circuit are optimized with 3D finite element (FE) simulations. A comparison between the analytic model, the FE calculation and the measurements on the real system proves good coherence.

Modeling, simulation and design of an axial flux machine using soft magnetic composite

Soft Magnetic Composites (SMC) allow the construction of electrical machines with three dimensional flux paths with maintainable effort, yielding high efficiency and outstanding power density. These are the typical requirements of automotive companies. The benefits of SMC-materials meet the demands of axial flux machines (AFM) very well, which offer a high power to weight ratio. This paper deals with the analysis and optimization of the AFM geometry. An analytical model defines the initial design parameters. Furthermore, the details of the magnetic circuit are optimized using 3D finite element (FE) simulations. Finally, the analytical model and the FE calculation are compared.