Finite element analysis of magnetic materials allows accurate prediction of losses and is crucial in the design of electromagnetic devices and products. Soft magnetic composites are an alternative to silicon steel laminations, yet the electromagnetic material properties are less well documented and include uncertainties which can lead to inaccurate iron and Joule loss computations. The microstructure of soft magnetic composites, which is based on ferromagnetic particles coated by inorganic resistive insulation, makes the process of iron loss prediction unique. Composite core materials require further attention by design engineers in terms of the effect of component size and pressing processes on core loss predictions, which for laminations uses the well-known Steinmetz law. This study accesses the existing soft magnetic composite core loss modelling trends using experimentally measured results. The challenges of estimating and using Steinmetz core loss coefficients via curve fitting approaches are discussed. The study indicates that soft magnetic composite components need to be treated differently to laminated iron cores. Modelling the composite materials in finite element software requires experimentally informed loss models to be able to accurately compute power losses under varying magnetic flux density and electrical frequency. An approach is suggested which can predict iron losses to within 7%, but is only validated for component cross sectional areas of 144 mm ² or less.

This paper presents a comprehensive review of the modern thermo-conductive materials that have potential to improve the heat extraction in electrical machines by conduction. Currently, there is a significant interest in thermal design and analysis of electrical machines as the demand for high power/torque density is substantially raised in applications such as marine, aerospace, e-mobility and rail. Thermal design engineering has become very important to develop smaller and more efficient electric motors, therefore electrical machine designers need to be more informed with the recent development in novel thermo-conductive (insulation) materials. Such developments can provide enhanced thermal characteristics for high power dense electrical machines. It is reported that high voltage electrical insulations can have more sophisticated thermal properties with the recent advancements in materials science. This study aims to inform electrical machine designers with and without a thermal background about recent thermo-conductive materials. Thus, a profound understanding can be gained in thermally conductive materials for the use of numerous applications in electrical machines for which thermal management is a crucial aspect of the overall multi-physics design and optimization process.

This paper focuses on the improved thermal performance of electrical machines by increasing the conductor fill factor. A comparative design study of integrated starter generator (ISG) is used as a case study to investigate the mechanical, electrical and thermal aspects of pressing coils. By performing quasi-static explicit dynamic simulations, deformation of insulation has been investigated. 1.25 mm diameter magnet wires are simulated and demonstrated to be compressible up to a 0.73 fill factor without observing insulation failure. Thermal conductivity enhancement of the stator windings at improved slot fill factor is investigated by performing steady state FEA thermal simulations and short time thermal transient tests.

In this paper, a permanent magnet alternator which presently relies on magnetic slot wedges is redesigned to give lower iron loss. The new segmented stator design is used as the basis for a validated loss study-comparing bonded lamination stacks with those held together with a punched notch. Segmentation is shown to improve the production process, reduce losses, and remove the need for wedges, while not significantly altering the acoustic performance. In the first series of prototypes, however, where notching is used to secure lamination packs, the process is shown to have adversely affected material properties of the nickel iron laminations and overall measured losses increased. In the second prototype, with thinner laminations and glued stacks, iron loss predictions and measurement agree and are less than the present slot wedge design.

In order to improve accuracy and reduce model setting up and solving time in the thermal analysis of electrical machines, the multi-material winding region is frequently homogenized. A typical electrical winding is an amalgam of the conductor material, electrical insulation, impregnation and imperfections like air cavities, which depend on the impregnation material and technique, among other factors. This makes the winding assembly one of the most challenging region in thermal design of electrical machines. This paper presents an analytical method for estimating the equivalent thermal conductivity of impregnated windings formed with round profile conductors. The existing analytical methods are limited to windings with conductor fill factor up to 40%. However, the ongoing development in fabricating windings enabled winding arrangements with much higher conductor fill factors, up to 85%. Such high conductor fill is very desirable as it reduces the winding DC power loss while improving the thermal path for the generated heat. Thus, providing a reliable analytical approach for the estimation of the equivalent thermal conductivity, applicable across a wide range of conductor fill factors, is very desirable. This paper presents a detailed description of the proposed approach, supplemented with measured data from tests on hardware winding material samples (WSs). An illustration of a practical use of windings with high conductor fill factors is also provided, highlighting the benefits of such configuration.

This paper describes the thermal modeling of a permanent magnet alternator (PMA). The principal focus is on, to investigate the effect of adding thermal paste into the machine end winding region. A thermal lumped parameter network is proposed to quantify the change in heat flow paths for a flange mounted alternator. The thermal model is implemented in Simulink, which allows many different heat paths to be easily combined. Since the addition of a thermal paste introduces new axial heat flow by conduction paths between the stator windings and frame, the developed thermal network considers the detailed heat flow paths in the PMA. The thermal network is extended to the machine frame and part of the mounting plate. It is shown that the axial heat flow has been improved by 5.6% for the PMA with the addition of the thermal paste. This in turn reduces winding temperature by around 10.5% at standstill dc tests. The model accuracy has been validated by performing finite-element analysis thermal simulations and experimental results.