arXiv subjects

Taha El Hajji

Publications and source records attributed to Taha El Hajji.

7 recordsLinked to original sources

arXiv2026

Electromagnetic Characterization of Magnetic Bar: Case of Square Cross-Section Shape

This paper presents a complete two-dimensional theoretical model for the electromagnetic behavior of square-section solid magnetic bars under sinusoidal loading. Through the application of Maxwell's equations within a Cartesian coordinate system and the integration of complex permeability, exact mathematical expressions are derived for mutual impedance, internal magnetic fields, flux, and core losses. Hyperbolic functions are utilized to separate the variables, enabling the accurate representation of edge flux accumulation and the 2D skin effect. In addition to mathematically decoupling eddy current and hysteresis losses, this formulation yields a new apparent permeability parameter. This parameter establishes a fast, reliable method for magnetic steel characterization that bypasses the extensive processing times associated with Finite Element Analysis (FEA). Numerical results over 1 Hz-1 MHz show the apparent relative permeability decreasing from 500 to 300 and a characteristic resistance peak near 700 kHz, marking the transition from volumetric to surface-dominated loss regimes.

math-ph↗

arXiv2026

Electromagnetic Characterization of Magnetic Ring: Case of Circular Cross-Section Shape

This paper introduces a comprehensive two-dimensional analytical model of a toroidal magnetic ring with circular cross-section under sinusoidal excitation. Applying Maxwell's equations in local polar coordinates within a complex permeability, the model derives analytical expressions for the internal magnetic field, magnetic flux, complex impedance, and total losses. It rigorously separates the contributions of eddy current losses, hysteresis losses, and winding losses, while explicitly incorporating the skin effect in the conductive core via Bessel functions. An expression for the apparent permeability is also provided, enabling the nonlinear core behavior to be mapped onto simplified linear material models. The resulting analytical model offers a computationally efficient and accurate foundation for standardized magnetic material characterization, such as Brockhaus and Iwatsu ring measurements, as a powerful alternative to 2D and 3D finite element analysis.

physics.comp-ph↗

arXiv2026

Electromagnetic Characterization of magnetic ring: Case of square cross section shape

This paper presents a comprehensive 2D analytical model of a toroidal magnetic ring with a square cross-section, subjected to sinusoidal excitation. By applying Maxwell's equations in local Cartesian coordinates and utilizing a complex permeability framework, the exact analytical expressions for the internal magnetic field, flux, complex impedance, and losses are derived. The model rigorously separates eddy current losses, hysteresis losses, and winding losses, explicitly accounting for the skin effect and complex permeability within the conductive core using separation of variables and hyperbolic functions. Furthermore, parameter for apparent permeability is expressed to map the core behavior onto simplified linear material models. The derivations establish a mathematical foundation highly suitable for standardized material characterizations, such as Brockhaus and Iwatsu ring measurements, by avoiding the heavy computational cost of 2D and 3D Finite Element Analysis.

eess.SY↗

arXiv2026

Investigation of Wound Field Synchronous Machines using Soft Magnetic Composites for Automotive Applications

This paper investigates the application of soft magnetic composites (SMCs) in the stators of wound field synchronous machines for automotive traction. While SMCs are traditionally employed in axial flux topologies, this study examines their use in radial-flux electrically excited synchronous machines (EESMs). Multiple SMC materials and lamination thicknesses are evaluated, with the optimal configuration combining a SMC material in the stator and 0.35 mm NO35 laminated steel in the rotor. This combination delivers improved torque and efficiency compared to conventional designs. When integrated into a full electric drive unit (EDU), this motor achieves 89.7% efficiency over the WLTP drive cycle, representing a 1.4 percentage point improvement over a reference permanent magnet synchronous machine-based EDU. The proposed solution eliminates rare-earth materials, reduces cost through thicker laminations, and offers environmental benefits through SMC utilization. This novel material combination, previously unexplored for radial EESMs, presents a promising direction for affordable, high-efficiency, rare-earth-free automotive traction machines.

eess.SY↗

arXiv2026

Defining the Magnetization State of LCF Magnets: From Material Properties to Motor-Level Metrics

Variable flux memory motors, which employ Low Coercive Force (LCF) magnets, achieve extended high-efficiency operation through controllable magnetization states. To address the need for a unified approach to defining and comparing the magnetization state (MS) across material and motor levels, this paper proposes four MS definitions: two based on intrinsic material properties-magnetic flux density B and magnetic polarization J-and two based on motor-level quantities-fundamental flux linkage and back-EMF components. These definitions are evaluated across the id, iq operating plane using finite element analysis on an interior PMSM with a hybrid magnet configuration (LCF and HCF: High Coercive Force) and a defined circuit setup. The results clarify the relationship between material-level behavior and measurable motor quantities. The proposed framework provides guidance for selecting appropriate MS metrics depending on the application objective, whether for material analysis, control implementation, or condition monitoring in variable flux machines.

eess.SY↗

arXiv2024

Circulating Currents in Electric Machines: Positive Impact of The End Windings Length on Losses

Circulating currents occurring in windings of electric machines received rising interest recent years. Circulating currents represent unwanted currents flowing between parallel-connected conductors. This phenomenon is due to various reasons such as asymmetries in the winding and differences in electric potential between parallel-connected conductors. This effect occurs both at no-load and on-load conditions, and always lead to uneven distribution of the current between the parallel conductors, therefore leading to higher losses, as proven in the authors' previous work. Circulating currents are occurring mainly due to asymmetries and electric potential difference in the active part, meaning that long end windings are advantageous to mitigate the effect of circulating currents. Losses due to circulating currents decrease at a rate proportional to the inverse square of the end windings length. The aim of this paper is to mathematically prove this property and present a case study application in an electric machine.

eess.SY↗

arXiv2024

Circulating Currents in Windings: Fundamental Property

Circulating currents in windings refer to unwanted electrical currents flowing between the parallel conductors of a winding. These currents arise due to several phenomena such as asymmetries, imperfections in the winding layout, and differences in electric potential between the parallel conductors. This effect is visible typically in windings of transformers, motors, or generators. At on-load condition, this is equivalent to having a current unevenly distributed between parallel conductors. Circulating currents have two main drawbacks: increased losses in windings and potential degradation of insulation over time. The former is an intuitive property that is widely acknowledged in the literature. This paper presents a formal proof of this fundamental property, building upon the authors' previous work and embedding it within a rigorous mathematical framework. The mathematical definition of circulating currents is provided, along with a case application in an electric machine.

eess.SY↗