Mehmet Caglar Kulan

This paper presents the design and multi-objective optimization of a six-limb magnetically integrated hybrid distribution transformer (HDT). The increasing demand for efficient and compact transformer solutions in modern distribution networks motivates the development of improved design methodologies. In this work, a detailed design procedure is established, including core geometry definition, winding configuration, and magnetic circuit considerations. A multi-objective optimization framework is formulated to minimize total transformer mass and power losses while satisfying operational constraints such as magnetic flux density and current density limits in the windings. Key design parameters, including core dimensions and winding configurations, are systematically varied to identify an optimal trade-off between material usage and performance. The optimization results show a noticeable reduction in total mass with a slight improvement in total losses, while all design constraints are maintained within acceptable limits. A laboratory-scale prototype was constructed to demonstrate the proposed magnetic configuration, and experimental validation was performed under steady-state, open-loop operating conditions to verify the voltage injection principle through the integrated control and extension windings. The presented approach offers a structured pathway for the design and optimization of HDT and can serve as a basis for further studies involving advanced control and operational strategies.

Different topologies for individual stator teeth as modular electric motor components are investigated via several different metrics such as finite element analysis (FEA), winding methodologies, and thermal performance during electrical power loading. These are easily quantifiable metrics which allow for the direct comparison of the different topologies, particularly with respect to the concentrated windings of the copper wire around the stator teeth. The paper assesses temperature rise, heat dissipation, and the role of air gaps within the copper wire windings. The results show that the winding via robot resulted in 30 (±5)% lower temperature rises on average compared to commercial (hairpin) winding systems, due to more ordered winding which results in larger air gaps between the wires. The air gaps appear to play a critical role in the thermal performance of the stator windings. It is also shown that the different topologies affect thermal performance during electrical loading, suggesting that the different topologies could be useful in different applications.

This paper presents the design, optimization, and validation of a dual three-phase yokeless and segmented armature (YASA) axial flux permanent magnet (AFPM) machine for aerospace actuators. The proposed 12-slot, 10-pole topology employs segmented soft magnetic composite (SMC) stator teeth integrated into an additively manufactured aluminium holder, combining modularity, weight reduction, and improved thermal conduction. A multi-objective optimization process based on 3D finite element analysis (FEA) was applied to balance torque capability and losses. The manufacturable design achieved a peak torque of 28.3 Nm at 1400 rpm and a peak output power of 3.5 kW with an efficiency of 81.6%, while limiting short-circuit currents to 14 Arms. Transient structural simulations revealed that three-phase short circuits induce unbalanced axial forces, exciting rotor wobbling—a phenomenon not previously reported for YASA machines. A prototype was fabricated and tested, with static torque measurements deviating by 8.6% from FEA predictions. By contrast, line-to-line back-EMF and generator-mode power output exhibited larger discrepancies (up to 20%), attributed to the frequency-dependent permeability and localized eddy currents of the SMC stator material introduced during EDM machining. These results demonstrate both the feasibility and the limitations of YASA AFPM machines for aerospace applications.

This paper presents a multiphysics, Life Cycle Assessment (LCA)-based design optimization framework for an interior permanent-magnet traction motor tailored to electric-vehicle duty. The workflow couples driving cycle realism, electromagnetic–thermal analysis, and life cycle assessment within a unified, computationally efficient process. Representative operating points are extracted from WMTC and ECE cycles using clustering, after which a multi-level Taguchi refinement searches the design space from coarse to fine. A weighted composite objective balances machine cost and life cycle cumulative emissions under hard constraints on torque capability and hotspot temperature. The optimized design satisfies performance and thermal limits while simultaneously reducing both cost and life cycle burden, as confirmed through phase-wise assessment of raw material, use-phase, and end-of-life contributions. Iterative improvements are accompanied by rising signal-to-noise ratios and reduced parameter-level spread, indicating greater robustness to operating variability. Overall, the study demonstrates that an LCA-driven, multiphysics-constrained optimization can deliver sustainable, high-performance IPM designs that are aligned with realistic vehicle operating conditions and readily adaptable to alternative motor and drive architectures.

Electric machines are crucial in modern industries, playing a substantial role in power genera-tion, manufacturing, transportation, and renewable energy. Consequently, extensive research is focused on enhancing their performance, making it essential to understand their thermal behavior for effective modifica-tions and improvements. While existing literature covers thermal effects in electric machines, the specific analysis of thermal conductivity in stator windings, a major contributor to energy losses, has remained sig-nificantly underexplored due to the complicated geometrical, material, and manufacturing factors. This paper presents a comprehensive review of methods and challenges related to characterizing the equivalent thermal conductivity of stator windings, categorizing them into analytical, numerical, and experimental approaches, with three sample levels (domain, motorette, and prototype). Furthermore, the paper introduces concepts of anisotropy, components, and available winding technologies to establish a solid foundation before discussing these methods. This review highlights the strengths and limitations of each method, emphasizing their needs and constraints to advance high-performance electric machines, and ultimately contributing to the evolution of more reliable and efficient electric machines.

Modular converters offer an effective solution for battery energy storage systems (BESSs) by lowering battery pack voltage levels and enabling additional functionalities, such as state of charge (SoC) and state of health (SoH) balancing, temperature regulation, and improved system reliability. However, conventional modular designs often require numerous additional components, including passive elements, switches, and sensing circuits. This paper proposes a modular multi-port converter (MMPC) BESS that combines energy conversion and battery management functions, leveraging the benefits of both modular and multi-port architectures. The proposed system demonstrates promising scalability and adaptability within the tested voltage and power ranges, with potential for extension to higher voltage and power applications through modular expansion. It also introduces an additional control layer, enhancing flexibility for control optimization and cost-effectiveness while improving reliability by reducing dependency on bypass switches. A prototype utilizing three dual-port converters managing six battery packs was developed. The experimental results confirm that the MMPC-based BESS achieves energy conversion and effectively balances the SoC among battery packs during both charging and discharging, under initial SoC mismatches.

Transverse flux machines (TFMs) with independent phases are suitable for aerospace applications, where fault tolerance is required. Their complex 3-D flux path can be accommodated by using soft magnetic composites (SMCs). However, core loss evaluation of SMC-based electrical machines is limited by the accuracy of calculation models, most of which have been applied under no-load conditions. Therefore, the aim of this article is to compare experimental power and losses in an SMC-based TFM with results given by the equivalent circuit (EC) and the finite-element method, thus providing a better insight of loss mechanisms. At 5000 r/min, results show a good agreement; however, at 400 r/min, the experimental power on the load is lower than expected for high power values. Further measurements and analysis indicate that great iron losses are affecting power production at low speeds. Therefore, choosing a high-resistivity SMC material for the stator cores, with a good performance regarding high-speed losses, may entail some uncertainties for low-speed operation due to the magnetic behavior of SMC under load conditions.

3-dimensional (3D) flux machines accommodate many design and analysis challenges. Transverse flux machines (TFMs) are mostly useful for low speed, high torque applications but in this research a fault tolerant transverse flux alternator with segmented stator has been prototyped and several important design and manufacturing challenges have been thoroughly investigated as different scenarios. The proposed machine consists of axially separated, 4-single phase to achieve low speed power of 40 Watts at 400 revolutions/minute (rpm). In addition, the machine must achieve several high-speed specifications at 15,000 rpm. It is demonstrated that the proposed TFM could be an alternative to more conventional radial flux machines in aerospace as validated within the paper. However, the necessity of stator segmentation and the use of soft magnetic composites for the proposed 3D flux machine lead to many important design and optimization considerations. Therefore, this paper investigates the manufacturing and material uncertainties in a TFM for an aerospace application. The results indicate that transverse flux alternator might be an option as an aerospace alternator but the peak performance of the prototype machine is still far from the 3D models investigated using finite element electromagnetic simulations.

A linear engine generator with a compact double-acting free piston mechanism allows for full integration of the combustion engine and generator, which provides an alternative chemical-to-electrical energy converter with a higher volumetric power density for the electrification of automobiles, trains, and ships. This paper aims to analyse the performance of the integrated engine with alternative permanent magnet linear tubular electrical machine topologies using a coupled dynamic model in Siemens Simcenter software. Two types of alternative generator configurations are compared, namely long translator-short stator and short translator-long stator linear machines. The dynamic models of the linear engine and linear generator, validated with lab-scale prototypes, are applied to investigate the influence of alternative topologies of the generator on system performance. The coupled model will facilitate the early design phase and reveal the optimal match of the key parameters of the engine and generator. Then, experimental tests on an integrated compressor cylinder-generator prototype were successfully performed, and it is shown that this concept is feasible and electrical power and compressed working fluid, such as air, can be generated by this prototype.

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.