Purpose This work aims to propose a novel post-fault direct torque control (DTC) scheme for induction motor drives supplied by an eight-switch three-phase inverter (ESTPI), implemented through the design of three new look-up tables. Design/methodology/approach A comprehensive analysis is performed to evaluate the effect of each voltage vector generated by the ESTPI on the stator flux, electromagnetic torque, DC-link capacitor voltages and common-mode voltage (CMV). To mitigate the capacitor voltage imbalance, a dedicated hysteresis comparator is incorporated to regulate the voltage difference between the DC-link capacitors. Torque ripple is reduced by eliminating vectors responsible for excessive torque pulsations, while CMV variations are minimized through the creation of two virtual vectors that replace those generating high CMV levels, effectively confining CMV within ± Vdc/6. Findings The validity and effectiveness of the proposed DTC strategy are confirmed through extensive simulation studies. By introducing three redesigned look-up tables and incorporating dedicated control mechanisms, namely, a hysteresis comparator for neutral point voltage (NPV) balance, the removal of torque-inducing vectors and the use of virtual vectors to constrain CMV, the proposed approach significantly enhances the drive’s post-fault performance. Originality/value The ESTPI, obtained by reconfiguring a faulty three-level NPC inverter, enables robust post-fault operation by maintaining balanced power delivery, reducing circuit complexity and preserving acceptable output voltage levels. However, when feeding induction motor drives, the performance of the ESTPI can be hindered by several critical challenges, including DC-link capacitor voltage imbalance, elevated torque ripple and fluctuations in CMV. Simultaneously addressing these issues is crucial to ensure stable, efficient and reliable motor-drive operation under fault conditions.

Purpose This study aims to develop an efficient level-set (LS)-based multi-objective topology optimization framework capable of handling strongly nonlinear electromagnetic design problems, and to demonstrate its applicability through the design of synchronous reluctance motors. Design/methodology/approach The proposed level-set adaptive switching method (LASM) combines an LS-based topology optimization scheme with an adaptive switching mechanism of weighting coefficients. The weights are automatically determined by solving a mixed-integer linear programming problem that maximizes the expected shape variation, and switching is triggered when objective improvement stagnates, deteriorates or oscillates. This dynamic framework enables continuous exploration of Pareto fronts in multi-objective design spaces. Findings Numerical experiments demonstrate that LASM achieves broader and more uniformly distributed Pareto fronts and improved design performance compared with conventional weighted-sum optimization. The obtained geometries maintain smooth and manufacturable boundaries, confirming the practicality of the proposed framework. Originality/value LASM builds upon the LS-based switching concept of Shigematsu et al. (2022) and extends it by introducing a shape-variation-driven automatic weight computation scheme and enabling a scalable application to three or more objectives. Through these extensions, LASM eliminates designer dependency in weight setting, enhances robustness against local minima and provides a practical and fully automated framework for multi-objective electromagnetic design.

Purpose This paper aims to propose a Physics Informed Neural Network (PINN) based method for the solution of inverse problems in magnetics, when the nonlinear characteristics of magnetic materials are included. Design/methodology/approach The proposed method is designed to estimate the current sources from a set of magnetic field measurement, in presence of nonlinear magnetic materials. The PINN constructed to solve this problem is based on the physics laws of magnetism that are used to solve the direct problem of calculating the field in a set of points given magnetization and currents. A loss function (backpropagating the error in the NN) evaluates the discrepancies between estimation and measurements and imposes the magnetic characteristics of the material. Findings The method has proven to be characterized by accuracy and low computational time if compared to more classical approaches which include regularization: in particular, the PINN that penalizes both measurement discrepancy and constitutive relation error can substantially improve source reconstruction in magnetostatics with magnetic materials. Originality/value To the best of the authors’ knowledge, the insertion of the constitutive error in the loss function proposed here is new and proves to be a step ahead in the utilization of PINN for the solution of nonlinear magnetic inverse problems. Furthermore, it paves the road for new applications in which inversion from data from complex systems can be a challenging task.

Purpose This paper aims to present a novel analytical approach based on the bipolar coordinates mapping method to determine the optimal magnet reduction (eccentricity) in surface-mounted permanent-magnet (SPM) and surface-mounted permanent-magnet motors for minimizing cogging torque. Furthermore, it formulates key motor performance parameters as functions of the magnet reduction factor and investigates the impact of optimal magnet shaping on motors with rotor eccentricity. Design/methodology/approach The core idea is to model the outer magnet surface and the slotted stator bore as eccentric circles. The bipolar mapping is then used to transform the slotted stator geometry into an equivalent slotless one, a condition known to minimize cogging torque. Solving the resulting mapping equations yields the optimal geometric parameters for magnet eccentricity. Findings The proposed method produces three distinct, physically valid roots (solutions) for the optimal magnet reduction. A key finding is the scalability of these solutions: the optimal values for a new motor can be obtained by scaling a reference motor’s solutions by the ratio of their rotor radii, thereby eliminating repetitive calculations. The method is universally applicable to radial, parallel and bread-loaf type SPM motors. Originality/value The primary originality of this work lies in the application of the bipolar coordinates mapping method to the magnet shape optimization problem. This provides a robust analytical framework for predicting optimal eccentric pole designs that effectively reduce cogging torque, even in the presence of static or dynamic rotor eccentricity. The derived performance formulations offer quick insights into the trade-offs involved.

Purpose The purpose of this study is to present a detailed and rigorous delay-dependent robust stability assessment of a shipboard microgrid (SMG) integrating a fuel cell. Design/methodology/approach In the SMG, communication time delays and uncertainties in system parameters adversely affect system frequency stability. An innovative approach is proposed that uses Kharitonov’s theorem in conjunction with the stability boundary locus (SBL) method to determine robust stability regions in the space of controller gains, considering both time delays and uncertainties. Findings This study comprehensively evaluates effects of time delays, parametric uncertainties and the fluctuations of renewable energy sources on these stability regions. Results demonstrate that robust stability regions shrink progressively with increasing time delays and higher levels of parameter uncertainty. Originality/value The integration of the SBL method with Kharitonov’s theorem is unique approach that enables the computation of robust stability regions for SMG in the existence of time delays and uncertainties. Results facilitate the effective synchronization of diesel generators and fuel cells to eliminate any discrepancies in system frequency following a disturbance.

Purpose This paper aims to perform a rigorous analytical evaluation of fully coreless axial-flux permanent magnet (AFPM) machines, targeting high-efficiency propulsion systems in unmanned vehicles. It focuses on the influence of permanent magnet geometries, winding topologies and current excitation types on key performance metrics. Design/methodology/approach A fully analytical framework is developed to evaluate 36 AFPM configurations. Using Coulombian charge and Biot–Savart laws, the magnetic field is modeled precisely. Back-electromotive force (EMF) and torque are derived under both sinusoidal and trapezoidal currents. Comparative analysis is performed based on total harmonic distortion (THD), torque ripple, efficiency and mass power density. Finally, the effectiveness and accuracy of the proposed approach are validated through 3D finite element simulations. Findings Performance is highly sensitive to the interplay between magnet shape, winding design and current waveform. Trapezoidal and curved rectangular windings, especially when paired with cylindrical or trapezoidal magnets and trapezoidal current, offer the best trade offs delivering high EMF, minimal THD, torque ripple reductions over 70% and efficiencies up to 97.5%. In contrast, triangular sector windings consistently yield the weakest performance. Originality/value This work introduces a fast, fully analytical tool for modeling and performance-driven optimization of coreless AFPM machines. It enables accurate, scalable evaluation of complex geometries and excitations without relying on computationally expensive numerical methods. The approach supports rapid design iteration and paves the way for next-generation high-speed, high-efficiency electric propulsion systems.

Purpose This study aims to propose a permanent magnet (PM) magnetization estimation method that utilizes the induced voltage measured by a pickup coil. Design/methodology/approach To efficiently minimize the objective function, a gradient-based optimization method supported by the adjoint variable method is applied. Findings The estimation of PMs magnetization was successfully carried out. Furthermore, the reconstructed induced voltages were quite similar to the target distribution. Originality/value The estimation method for PM magnetization using induced voltage at pickup coil located on the airgap of surface permanent magnet synchronous motors derived from rotor rotation.

Purpose The purpose of this study is to propose an effective and computationally efficient modeling technique for the analysis of closed-loop AC-DC Boost power factor correction converters. This research aims to simplify the complex analysis of both power and control circuits by transforming dynamic differential equations into purely algebraic forms, thereby reducing computational costs without sacrificing accuracy. Design/methodology/approach The method is based on the algebraization of dynamic circuit elements, such as capacitors and inductors, using a first-order Taylor series expansion. This transformation allows dynamic components to be modeled as equivalent resistive circuits with updated sources at each simulation step. This study uses modified nodal analysis (MNA) to derive a unified algebraic system equation that integrates both the power stage and the control loop – specifically Average Current Mode control – within the same discrete-time framework. Findings Simulation results for Boost power factor correction converters operating in both Continuous Conduction Mode and Discontinuous Conduction Mode validate the accuracy of the proposed model against conventional Backward Euler methods and commercial software like PSIM and MATLAB/Simulink. The findings of this study demonstrate that the proposed algebraic approach achieves a significant reduction in execution time (approximately 30% – 40%) and memory utilization (approximately 40%–60%) compared to traditional numerical integration methods. Originality/value The originality of this work lies in the unified algebraic formulation that treats switching devices, dynamic elements and digital control loops consistently within the modified nodal analysis framework. Unlike conventional hybrid or averaged models, this explicit discrete-time representation captures instantaneous interactions in both Continuous Conduction Mode and Discontinuous Conduction Mode without requiring distinct state-space models or iterative matrix inversions. This study offers a computationally lightweight and pedagogically transparent tool suitable for real-time analysis and digital control prototyping.

Purpose The purpose of this paper is to present a precise two-dimensional (2D) analytical approach for forecasting the open-circuit magnetic field distribution in slotted permanent magnet (PM) pseudo direct drive (PDD) machines featuring surface-mounted magnets. Design/methodology/approach Using the method of separation of variables, the Laplace and Poisson equations are solved to determine the radial and tangential components of the magnetic flux density within the inner and outer air gaps. The configuration of the magnets is regarded as radial. Findings An analysis of the outcomes derived from the suggested approach in relation to the results produced by the finite element method (FEM) indicates that, notwithstanding the geometric complexities involved, the formulation of the boundary value problem for predicting the magnetic field is effectively executed. Originality/value The effectiveness and accuracy of the proposed method are evaluated on two distinct sizes of slotted PDD machines. The integration of the presented analytical technique with meta-heuristic methods can be readily used for the optimal design of PDD machines.

Purpose To mitigate the inherent torque ripple in flux-reversal machines (FRMs), this study aims to propose a synergistic reconstruction topology. By modulating air gap harmonics and suppressing inter-pole leakage, this configuration resolves the conflict between torque density and stability, achieving significantly enhanced torque performance. Design/methodology/approach First, a synergistic reconstruction topology is proposed to unify stator, rotor and magnet designs. Second, to address high-dimensional conflicts, a hierarchical optimization strategy based on the Pearson Correlation Coefficient (PCC) is developed. The electromagnetic performance is rigorously evaluated using 2D Finite Element Analysis (FEA) based on the Maxwell Stress Tensor principle. Finally, a comprehensive comparative analysis against a conventional FRM is conducted under no-load, rated-load and overload conditions to validate the performance superiority. Findings The results indicated that the motor exhibited the best overall performance. Compared to traditional FRMs, it features increased harmonic components, reduced interpole leakage, 22.8% improvement in average torque and 57.2% reduction in torque ripple. Originality/value This study proposes a synergistic reconstruction topology and a PCC-based optimization strategy. Beyond establishing a generalizable design framework, the work demonstrates industrial feasibility using standard materials. The achieved 57.2% ripple reduction and high torque density offer significant economic benefits through reduced raw material consumption and maintenance costs, bridging theoretical innovation with practical engineering value.