This paper describes a fast approach for synchronous reluctance machine flux linkage mapping considering the cross-saturation effects. The rapid prediction of the flux maps <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ<i>_d</i></b> ( <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>i</i><i>_d</i>,<i>i</i><i>_q</i></b> ) and <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ<i>_q</i></b> ( <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>i</i><i>_d</i>,<i>i</i><i>_q</i></b> ) only requires the data (from finite element analysis or measurements) along the boundaries of the range to be mapped. To this purpose, two proper functions are defined to predict the effect of cross saturation based on the coenergy variation. The two analytical functions can be computed directly from the data acquired on the boundaries of the ( <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>i</i><i>_d</i>,<i>i</i><i>_q</i></b> ) current plane depending respectively on <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>i</i><i>_d</i></b> and on <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>i</i><i>_q</i></b> values. The method is applied to predict the flux linkage maps of a synchronous reluctance machine. The results from the semi-analytical method are compared to the full finite element analysis approach and with measurements. In the last part of the paper, different saturation models, based on a limited set of simulations, are compared, showing the new proposed method's potential, against other simplified approaches for a fast mapping.

This paper deals with the design of a 200kW/ 370Nm, induction machine for electrical vehicles traction system. The design aims to enhance the performance of the current induction machine technology for mass production making it suitable to be a rare earth free solution for electric vehicle applications. To this extent, suitable materials have been analyzed and selected, also by using of mechanical analysis and experimental data. Rotor die-casting, hairpin stator winding and specific cooling systems have been adopted within the proposed solutions. Extensive analytical and numerical methods are used for performance evaluation all over the full speed range of the machine.

This paper presents coupled electromagnetic (EM)–thermal modelling of the steady-state dynamic performances, such as torque speed curve and the efficiency map, for surface-mounted permanent magnet machines. One important feature of such a model is that it considers the demagnetization caused by magnet temperature rise at different rotor speeds. EM-only simulations, which often assume that the machines operate under constant temperature, have been widely used in the literature. However, the interaction between EM and thermal performances could lead to very different dynamic performance prediction. This is because the material properties, e.g., magnet remanence, coercivity, and copper resistivity are temperature-dependent. The temperature rise within electrical machines reduces torque/power density, PM eddy current losses, and iron losses but increases copper loss. Therefore, the coupled EM–thermal modelling is essential to determine accurate temperature variation and to obtain accurate EM performances of electrical machines. In this paper, the coupled EM–thermal modelling is implemented for both modular and non-modular machines to reveal the advantages of the modular machine under different operating conditions. The results show that the modular machine generally has better dynamic performance than the non-modular machine because the introduced flux gaps in alternate stator teeth can boost both EM and thermal performance.

Oil jet cooling and hairpin windings have become popular in electrical machine design for modern electric vehicles. In recent years, these two technologies are often combined and can be found in many commercial products. The highly effective cooling capability of oil jets and the high thermal conductance of hairpin windings greatly benefit the machine performance metrics. However, published quantitative literature on this topic is relatively scarce. This article presents experimental results and practical insights of oil jet cooling on the end region of hairpin windings. Temperature distribution, heat transfer coefficient, and cooling efficiency are all investigated. Consistent temperature profiles are observed throughout the range of flow rates. Moreover, the effects of using different types of oil and inclination angles are researched as well. Analysis of variance indicates that these two factors affect various aspects of the oil jet cooling’s performance. Results are also compared against data obtained from previous studies on oil spray cooling. This study can help engineers implement oil jet cooling in machine designs with hairpin windings.

This article investigates an advanced thermal management method adopting ferrofluid (FF) for improving the end-winding cooling of permanent magnet (PM) machines. An oil-based liquid with nano-sized ferromagnetic particles (which is known as FF) is used to fill in the cavity around the end windings. This is to establish an effective heat flux path between the end winding that is often regarded as hot spot in electrical machines and the external cooling system, i.e., water jacket, to improve the cooling performance of the PM machines. This improvement does not only result from the higher thermal conductivity and thermal expansion of the nanofluid with metal particles but also from strong thermomagnetic convection generated by the magnetic body force of the ferromagnetic particles within the FF. Multiphysics models considering the interaction between the electromagnetic field, the heat transfer, and the fluid dynamics have been built to study the thermal performances of a PM machine under different load conditions. Several factors affecting the thermomagnetic convection, such as the temperature-dependent magnetization curve of the FF, the concentration, and different ferromagnetic materials as well as different current densities, have been investigated to analyze their influences on cooling performance. One major finding is that, compared with other coolant without magnetic body force, the FF can significantly reduce machine peak temperature, e.g., by around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${36.4}~^{\circ }\text{C}$ </tex-math></inline-formula> when the current density is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {22.1}~\text {A} / {\text {mm}}^{ \boldsymbol {2}}$ </tex-math></inline-formula> .

This paper investigates magnet demagnetization characteristics of the modular permanent magnet machine. The influence of flux gaps on magnet flux density, losses distribution, torque and demagnetization are analyzed for different operating conditions. The magnet demagnetizations caused by three sources, such as the PM field, the armature field, and the magnet temperature rise, are individually investigated using the frozen permeability method. Furthermore, coupled electromagnetic (EM)-thermal modelling is also adopted in this paper to fully reveal the advantages of the modular machine in improving machine EM performances. This is essential due to the temperature-dependent properties of the machines, such as the magnet remanence, coercivity, and copper resistivity. For comparison propose, the EM performances with a particular focus on the demagnetization withstand capability for both the modular and non-modular machines are investigated based on the EM-thermal coupling. It is found that, compared to the non-modular machine, the modular machine can achieve higher torque, higher efficiency, and better demagnetization withstand capability.

The hairpin winding technology is increasing its impact in the industrial and automotive sectors, thanks to the well-known advantages in terms of motor performance and manufacturing process. Since wave patterns must be adopted, there are significant differences compared to the traditional winding design, in particular concerning the parallel paths conductors disposition. Design rules for hairpin windings with parallel branches are proposed in literature to avoid circulating currents and extra losses. Due to the nonlinearity or in case of short pitched windings, some patterns present a weak symmetry and parasitic currents can circulate. This paper investigates the circulating currents issue in commonly adopted hairpin winding patterns, analysing working points with different saturation levels and speeds. New patterns for more than 2 parallel branches are proposed with reduced parasitic currents with respect to the already known solutions. In the second part of the paper, fractional slot winding configurations are proposed.

Thermal management is an issue with all electrical machines, including electric vehicle drives and wind turbine generators. Excessively high temperatures lead to loss of performance, degradation and deformation of components, and ultimately loss of the system. Cooling of Rotating Electrical Machines: Fundamentals, modelling, testing and design provides a foundation of heat transfer and ventilation for the design of machines. It offers a range of practical approaches to the thermal design, as well as design data and case studies. Chapters cover fundamentals of heat transfer, fluid flow, thermal modelling of electrical machines, computational methods for modelling ventilation and heat transfer such as finite element methods and computational fluid dynamics, thermal test methods, and application of design methods. Intended for engineers and researchers working in either academia or machine design companies, this book provides sound insights into the phenomena of heat transfer and fluid flow, giving readers an understanding of how to approach the thermal design of any machine.

This work investigates circulating currents and additional losses in hairpin windings with multiple parallel paths when a weak symmetry pattern is adopted. The theoretical rules for designing hairpin windings may lead to configurations not completely preventing parasitic currents in the parallel branches, especially in heavy saturation conditions. Often, the proposed configurations in the literature present a weak symmetry between the parallel branches. This paper considers a typical hairpin winding configuration to compute the actual currents in the parallel paths. For this purpose, machine models are driven by an external three-phase circuit and finite element analyses are carried out. The main goal is to explain the causes of circulating currents. The analysis is repeated using different rotor topologies and keeping respectively the same stator design, overall machine volume and hairpin winding pattern to look into the different effects in windings induced by parasitic currents.