The magnetization process of magnetic materials is still insufficiently modeled to adequately consider it in a numerical simulation of e.g. electrical machines. The basic electromagnetic relationships are already described by the Maxwell equations, but further material models are required to consider special material-dependent effects which are relevant. This thesis discusses a general methodology for the consideration of magnetic material in finite element analysis models and for this purpose enhances suitable material models from the state of the art. The focus is on models with empirical equations and physical parameters that can be extracted directly from measurements. Starting from generally valid model approaches for soft magnetic materials, this thesis concentrates on hard magnetic materials. The emphasis is on high-energy rare-earth magnets, as they represent the most promising choice for technically relevant electrical machines. In contrast to soft magnetic materials, effects such as anisotropy, hysteresis, and dependencies on temperature and magnetization history are much more pronounced. In particular, a simple consideration of anisotropy and hysteresis represents a challenge for modeling. For hard magnets, detailed series of measurements of a pulsed-field magnetometer on samples of high-energy rare-earth magnets serve as a starting point. The model allows to predict the magnetic field and the resulting magnetization during and after any transient magnetization process. The properties of the model are verified by numerical simulation using technically and physically relevant examples. The numerical examples illustrate which practical questions have to be investigated using the model for the simulation in order to ensure safe magnetization of a magnet system.

The design of modern electric machines aims to increase the power density and enhance the machine’s reliability. Applying effective cooling systems is a practical approach to elevate the quantity of power density. Among a variety of modern cooling technologies, direct oil cooling has found particular attention in recent years. From the perspective of electrical machines, the insulation system is vital in introducing cooling fluids directly into the inner space of the machine. Due to the presence of electrical voltage potential in the winding insulation system, even small damage to insulation materials may result in electrical failure of the winding insulation system or the operation of the entire electrical machine. Therefore, it is compulsory to have a fundamental understanding of the influence of cooling oils on the behaviour of the insulation system. In this study, the thermal, mechanical and electrical ageing of the insulation system in an oil environment is analysed with experiments and numerical simulations. The effect of conductive contaminants in the oil on the dielectric properties of the insulation system is discussed. Particularly, the material compatibility of E-fluids with the insulation system is studied in deep. Through this study, the machine designers are aware of the weakness of the state-of-the-art insulation system in oil-cooled electrical machines. Meanwhile, it is gained for the E-fluid manufacturers how the E-fluid should be enhanced to ensure a safe application in electrical machines.