Search Results (97)

This paper presents an application-oriented evaluation of a 130 kW interior permanent magnet synchronous motor (IPMSM) for C-segment electric vehicle (EV) traction by linking sequentially coupled multiphysics analysis with WLTP-based vehicle system-level simulation. Conventional motor performance evaluation is based on single-physics analysis at a limited number of operating points. This approach is insufficient to capture nonlinear characteristic variations under changing operating conditions or to reflect realistic driving environments. To overcome this limitation, sequentially coupled multiphysics analysis incorporating electromagnetic, thermal, and structural characteristics was performed, and the resulting loss data were incorporated into a vehicle system-level simulation model. The WLTP Class 3b driving cycle was applied to quantitatively evaluate energy performance under realistic driving conditions. The results show that the designed IPMSM satisfies the target output power of 130 kW, while its electromagnetic, thermal, and structural characteristics, including torque ripple, back-EMF, winding temperature, permanent magnet temperature, and rotor stress, remain within acceptable limits. The system-level analysis further indicates that the motor operating points during driving are predominantly distributed in the high-efficiency region, and that the final energy economy considering regenerative braking reaches 5.59 km/kWh, with an estimated maximum driving range of 352.58 km on a single charge. These results indicate that the combined motor-level and vehicle-level numerical evaluation can provide useful design-stage information for assessing high-power-density EV traction motors. Full article

With the advancement of new energy technologies and the demand for intelligentization, hydraulic cylinders in crane booms are gradually being replaced by electric cylinders. However, electric cylinders may induce an initial retraction phenomenon during the crane startup phase when the electromagnetic torque has not yet matched the lifting load. To address this problem, this paper proposes a load-aware position switching control method for an electric crane boom with an integrated brake mechanism. In the braking phase, a fixed-time convergence controller combined with a radial basis function neural network observer is used to build up the holding torque of the permanent-magnet synchronous motor (PMSM) rapidly under uncertain load torque. After the safety current threshold is satisfied and the brake is released, the control law switches to a feedforward Proportional–Integral (PI) controller for position tracking. The switching threshold is derived from the estimated load torque and the PMSM torque constant, and a hysteresis/dwell-time condition is introduced to avoid chatter near the switching boundary. Simulation and experimental results show that the method effectively reduces the initial retraction of the boom. Full article

The rotational evolution of pulsars is governed by torque mechanisms whose mathematical structure encodes fundamental symmetries of the underlying physics. We demonstrate that the standard spin-down equation $\dot{f}=-sf-r{f}^3-g{f}^5$ derives from a discrete antisymmetry requirement, namely invariance of the torque under reversal of rotation sense, which restricts the frequency dependence to odd integer powers. We show that physically motivated plasma processes systematically break this symmetry, introducing fractional frequency exponents: viscous Ekman pumping at the crust–superfluid boundary layer ($f^{3/2}$), magnetohydrodynamic turbulent dissipation via Kolmogorov and Sweet–Parker cascades ($f^{10/3}$, $f^{11/3}$), non-linear superfluid vortex dynamics ($f^{5/2}$), and saturated r-mode oscillations ($f^{7-2\beta }$). The central result is an exact analytical resolution of the long-standing Crab pulsar braking index puzzle: the observed $n=2.51\pm 0.01$, which has defied explanation for nearly four decades, emerges naturally from the superposition of magnetic dipole radiation ($\dot{f}\propto f^3$) and boundary layer Ekman pumping ($\dot{f}\propto f^{3/2}$), with analytically derived coefficients yielding a dipole-component surface field $B_p=6.2\times {10}^{12}$ G—higher than the standard $\sqrt{P\dot{P}}$ estimate of $3.8\times {10}^{12}$ G, because that formula conflates dipole and non-dipole torques, but lower than applying the Larmor formula to the full spin-down rate ($7.6\times {10}^{12}$ G), since $32.7\%$ of the total torque is non-radiative boundary-layer dissipation. We develop the Riemann–Liouville fractional calculus formalism for these equations, showing that fractional derivatives break time-translation symmetry through intrinsic memory effects, with solutions expressed in terms of Mittag-Leffler and Fox H-functions that interpolate continuously between exponential (fully symmetric) and power-law (scale-free symmetric) relaxation. Lambert–Tsallis $W_q$ functions with non-extensive parameter q encoding broken statistical symmetry enable equation-of-state-independent inference of neutron star compactness and tidal deformability. Our framework establishes a unified symmetry-based classification of pulsar spin-down mechanisms and predicts frequency-dependent braking indices evolving at rate $\mathrm{d}n/\mathrm{d}t\sim 2\times {10}^{-4}$ yr⁻¹, yielding $\mathrm{\Delta }n\approx 0.01$ over 50 years—testable with current pulsar timing programmes. The formalism provides a coherent theoretical foundation connecting plasma microphysics at the neutron star interior to macroscopic observables in electromagnetic and gravitational wave channels. Full article

With the expansion of urban rail transit, increased train operation density, and the large-scale grid integration of renewable energy such as offshore photovoltaic power, traction power supply systems face stricter requirements for operational safety, power supply reliability and energy utilization efficiency. Offshore photovoltaic power, integrated into the traction power supply network via flexible DC transmission technology, promotes renewable energy consumption, but its random and volatile output overlaps with time-varying traction loads, increasing the complexity of DC-side fault characteristics and protection control. Flexible DC technology is a core direction for next-generation traction substations, and three-level converters (key energy conversion units) have advantages over traditional two-level topologies. However, their P-O-N three-terminal DC-side topology introduces new faults (e.g., PO/ON bipolar short circuits, O-point-to-ground faults), making traditional protection strategies ineffective. In addition, wide system current fluctuation (0.5–3 kA) and offshore photovoltaic power fluctuation easily cause fixed-threshold protection maloperation, and the coupling mechanism among modulation strategies, DC bus capacitor voltage dynamics and fault current paths is unclear. To solve these bottlenecks, this paper establishes a simulation model of the system based on the PSCAD/EMTDC(A professional simulation software for electromagnetic transient analysis in power systems V4.5.3) platform, analyzes the transient electrical characteristics of three-level converters under traction and braking conditions for typical faults, clarifies the coupling mechanism, proposes a condition-adaptive fault identification strategy, and designs a reconfigurable fault energy handling system with bypass thyristors and adaptive crowbar circuits. Simulation and hardware-in-the-loop (HIL) experiments show that the proposed scheme completes fault identification and protection within 2–3 ms, suppresses fault peak current by more than 70%, limits DC bus overvoltage within ±10% of the rated voltage, and has good post-fault recovery performance. It provides a reliable and engineering-feasible protection solution for related systems and technical references for similar flexible DC system protection design. Full article

To respond to carbon-neutrality policies, interest in transportation powered by eco-friendly energy has increased. These systems require high-efficiency power conversion stages that enable bidirectional operation for driving and regenerative braking, where full-bridge converter topologies are widely adopted. However, harmonics in full-bridge converters can degrade efficiency and power density and cause electromagnetic compatibility issues. Therefore, the harmonic frequency bands and amplitudes must be accurately predicted. A single-variable Fourier series can estimate the baseband and carrier harmonics. However, the fundamental frequency of motor drive systems and railway vehicles generates the sideband harmonic which is determined by the baseband and carrier harmonics. Therefore, accurately predicting the sideband harmonics is difficult when using a single-variable Fourier series. This paper proposes a double Fourier series (DFS)-based sideband harmonic analysis of a full-bridge converter. To validate the applicability of the proposed method to various full-bridge based systems, four sets of results are compared over multiple combinations of the fundamental and carrier frequencies, including DFS without deadtime, DFS with deadtime, simulation results, and experimental results. Full article

An accurate prediction of aircraft wheel and brake (W&B) temperatures is increasingly important for ensuring landing gear safety, supporting turnaround decision-making, and allowing for more effective condition monitoring. Although the thermal behavior of brake assemblies has been studied through component-level testing, analytical formulations, and numerical simulation, current understandings remain fragmented and limited in operational relevance. This paper discusses research across landing gear sensing, thermal modeling, and data-driven prediction to evaluate the state of knowledge supporting a non-intrusive, temperature-centric monitoring framework. Methods surveyed include optical, electromagnetic, acoustic, and infrared sensing techniques as well as traditional machine-learning methods, sequence-based models, and emerging hybrid physics–data approaches. The review synthesizes findings on conduction, convection, and radiation pathways; phase-dependent cooling behavior during landing roll, taxi, and wheel-well retraction; and the capabilities and limitations of existing numerical and empirical models. This study highlights four core gaps: the scarcity of real-flight thermal datasets, insufficient multi-physics integration, limited use of infrared thermography for spatial temperature mapping, and the absence of advanced predictive models for transient brake temperature evolution. Opportunities arise from emissivity-aware infrared thermography, multi-modal dataset development, and machine learning models capable of capturing transient thermal dynamics, while notable challenges relate to measurement uncertainty, environmental sensitivity, model generalization, and deployment constraints. Overall, this review establishes a coherent foundation for thermography-enabled temperature prediction framework for aircraft wheels and brakes. Full article

As a highly integrated and compact power unit, the motor-pump finds critical applications in emerging electric vehicle (EV) domains such as electro-hydraulic braking and steering systems, where its vibration and noise performance directly impacts cabin comfort. A key factor limiting its NVH (Noise, Vibration, and Harshness) performance is the electromagnetic vibration and noise induced by the cogging torque of the built-in brushless DC motor (BLDCM). Traditional suppression methods that rely on stator auxiliary slots exhibit certain limitations. To address this issue, this paper proposes a collaborative optimization method integrating multi-parameter scanning and response surface methodology (RSM) for the design of auxiliary slots on the motor-pump’s stator teeth. The approach begins with a multi-parameter scanning phase to identify a promising region for global optimization. Subsequently, an accurate RSM-based prediction model is established to enable refined parameter tuning. Results demonstrate that the optimized stator structure achieves a 91.2% reduction in cogging torque amplitude for the motor-pump. Furthermore, this structure effectively suppresses radial electromagnetic force, leading to a 5.1% decrease in the overall sound pressure level. This work provides a valuable theoretical foundation and a systematic design methodology for cogging torque mitigation and low-noise design in motor-pumps. Full article

This paper presents an innovative concept for the adaptive transformation of decommissioned coal mine shafts into advanced reduced-gravity research facilities, addressing both post-mining land management and continuous advancements in microgravity research. The proposed solution leverages existing underground infrastructure to create an exceptionally long drop tower, approximately 900 m, surpassing the operational capabilities of all current global facilities. The facility employs electromagnetic propulsion and braking systems compatible with maglev technology, enabling extended microgravity durations and the precise simulation of multiple planetary gravity environments. Comprehensive numerical simulations, taking into account realistic mining shaft geometries, aerodynamic resistance, and mechanical vibration isolation, demonstrate that the system achieves free-fall periods of at least 10 s, which will be longer in the case of a capsule drop for research in reduced-gravity conditions (controlled deceleration of the capsule during the drop). The six-point suspension system effectively isolates experimental payloads from vibrations generated during descent. Beyond technological innovation, the facility exemplifies multidimensional sustainability by integrating scientific advancement with regional economic revitalization, employment generation for mining communities, industrial heritage preservation, and alignment with European Green Deal objectives. This globally unique research center would provide unprecedented opportunities for materials science, space biology, and industrial experimentation, while demonstrating innovative repurposing of post-mining assets. Full article

This study proposes an electromagnetic balance-based structural design and shim plate application to improve the response characteristics of an electromagnetic brake. Electromagnetic brakes typically experience response delay due to inductive effects and residual magnetic flux after power-off. To address this issue, the inner and outer thicknesses of the stator were parameterized to achieve balanced magnetic flux distribution, and a non-magnetic shim plate (SUS 304) was applied to reduce residual flux within the electromagnet. Finite element analysis (FEA) was conducted to evaluate the influence of structural parameters on the magnetic flux balance and attractive force. The optimized stator geometry provided a stable electromagnetic balance, and the shim plate effectively reduced the response delay and improved the overall response performance compared with the conventional design. These findings demonstrate that the proposed electromagnetic balance design combined with shim plate application is an effective approach to enhance the reliability and control responsiveness of electromagnetic brakes, with potential applicability to robotic and industrial actuator systems. Full article

The introduction of Poland (2004) and Croatia (2013) into the European Union presented the challenge of modernising ageing rail rolling stock equipped with DC traction motors, operating under limited financial and technical resources. In both countries, older and modernised vehicles remain largely equipped with DC traction motors: in Poland, about 86% of electric locomotives, 77% of EMUs, 68% of trams, 29% of metro trains (expected to fall to 0% by 2025), and 8% of trolleybuses use this technology. Although these numbers have declined rapidly over the last decade, DC traction motors have played a crucial transitional role, enabling effective modernisation and extending vehicle life while postponing the costly purchase of new AC-motor rolling stock. In 2022, Ukraine became an EU candidate country and faced similar challenges in aligning its transport sector with European standards. This review analyses the re-engineering strategies adopted in Poland and Croatia, focusing on the technical, organisational, and policy measures that supported sustainable fleet renewal. Using a comparative method based on documentation, case studies, and reports (2004–2024), this study shows that re-engineering can extend service life by 15–25 years, reduce energy use by up to 20%, and improve reliability by 30–40%. Recommendations are outlined for Ukraine’s future modernisation strategy. Full article

In this study, to address the problems of the redundant safety and mass production of electro-mechanical braking (EMB) structures that are widely used in distributed drive electric vehicles (DDEV), we designed a compact dual-disc electromagnetic–EMB composite brake. The composite brake embeds an electromagnetic brake into the original friction disc, which realizes an organic combination of the friction and electromagnetic brakes. Electromagnetic braking has the advantages of no friction, a rapid response, and a high-speed braking effect, which can effectively improve the reliability and mechanical redundancy of composite braking systems. The braking system comprises regenerative, electromagnetic, and friction braking, which are typical hybrid systems. We designed a mode-switching control strategy for a composite braking system based on the hybrid control theory. MATLAB/Simulink were used to model each system and set different simulation conditions. The simulation results showed that, under different working conditions, the hybrid automata control strategy had a fast response speed, small overshoot error, and adapted to different road conditions. The feasibility of the redundant design of the electromagnetic–friction–regenerative composite braking structure and the rationality of the hybrid automata control strategy design were verified. Full article

This study presents a novel conceptual model to explain the differential rotation within Earth’s layers, a phenomenon observed through seismic wave studies but not fully understood. While geodynamo theory and electromagnetic coupling models have been proposed to explain this phenomenon, our model offers an alternative perspective focusing on the Moon’s tidal forces. Our model proposes that the Moon’s tidal forces play a crucial role in this process, acting as a braking mechanism on Earth’s rotation. We hypothesize that these tidal forces initially decelerate the Earth’s crust and mantle, with this effect sequentially transmitted to deeper layers. A key aspect of our model is the role of the liquid outer core in mediating this process. We suggest that the liquid state of the outer core delays the transmission of tidal friction, resulting in differential rotation between layers in contact with it. This delay mechanism provides a potential explanation for the observed rotational differences between the mantle and core. Our model demonstrates that about 66,000 years after the Moon’s formation, the tidal force slowed the crust–mantle rotation by approximately 5.5 degrees per year more than the core. Furthermore, we estimate that the frictional heat generated at the boundaries of differential rotation is about 0.3478 TW. At this rate, the outer core temperature would increase by approximately 13.4 K per billion years. This thermal effect may have significant implications for the long-term evolution of Earth’s core, potentially slowing its cooling rate and maintaining its liquid state. Our model thus provides a new perspective on the interplay between lunar tidal forces, Earth’s internal structure, and its thermal evolution, offering insights into the complex dynamics of our planet’s interior. Full article

To study the influence of speed brake deflection on remote sensing grayscale images and the radar cross section (RCS) of aircraft, we present a comprehensive method based on remote sensing modeling and dynamic electromagnetic scattering. The results indicate that grayscale images from ground remote sensing can capture the hierarchical information of various reference objects and water bodies. When the target aircraft enters the observation area, complex ground reference objects may blur the grayscale features of the speed brake. The RCS of the speed brake shows strong dynamic characteristics under the example of the forward azimuth, where the maximum variation can reach 43.433 dBm². When the speed brakes on both sides dynamically deflect, the aircraft’s RCS in the lateral azimuth will fluctuate significantly in the first half of the observation time, and those in the forward and backward azimuths will show clear dynamic characteristics in the second half of the observation time. Low grayscale ground reference and water body boundaries/areas are beneficial for distinguishing the deflection of the deceleration plate. The comprehensive method proposed here is effective for studying remote sensing grayscale images and the dynamic RCS of aircraft under speed brake deflection. Full article

Herein, a three-dimensional mathematical model was established to investigate the metallurgical behavior of liquid steel in a funnel-shaped mold equipped with single-ruler electromagnetic braking (EMBr). The effects of mold thicknesses, electromagnetic intensity, and casting speed in flow behavior were investigated. The results indicate that with EMBr, multiple pairs of induced current loops are present in the horizontal section of the magnetic pole center, distributed in pairs between the jets and broad faces. The Lorentz force acting on the main jet, which impacts the downward and upward flow at adjacent broad faces, is opposite in direction. Increasing mold thickness results in a larger jet penetration depth, leading to a higher meniscus temperature near the narrow faces accompanied by elevated velocity and turbulent kinetic energy. EMBr can lead to a decrease in shell thickness and an improvement in its uniformity at mold exit. For the thickened mold, as the magnetic flux density increases and the casting speed decreases, the penetration depth of jets and velocity near the narrow faces and meniscus decreases. The shell thickness decreases as the casting speed increases, with the lowest non-uniformity coefficient of 6.78% observed at a casting speed of 5.0 m/min. Full article

This article presents the simulation results of synchronization of a permanent magnet synchronous generator (PMSG) dedicated for a hydroelectric plant without power converter devices. The proposed machine design allows to connect a generator to the grid in two different ways. With the first method, the machine is connected to the grid in a similar way as in the case of an electrically excited synchronous generator. The second method is a direct line-start process based on asynchronous torque—similar to asynchronous motor start. Both methods can be used alternately. The advantages of the presented design are elimination of converter devices for starting the PMSG, possibility of use in small and medium hydroelectric power plants, operation with a high efficiency and high power factor in a wide range of generated power, and smaller dimensions in comparison to the generators currently used. The described rotor design allows for the elimination of capacitor batteries for compensation of reactive power drawn by induction generators commonly used in small hydroelectric plants. In addition, due to the high efficiency of the PMSG, high power factor, and appropriately selected design, the starting current during synchronization is smaller than in the case of an induction generator, which means that the structural elements wear out more slowly, and thus, the generator’s service life is increased. In this work, it is shown that PMSG with a rotor cage should have permanent magnets with an increased temperature class in order to avoid demagnetization of the magnets during asynchronous start-up. In addition, manufacturers of such generators should provide the number of start-up cycles from cold and warm states in order to avoid shortening the service life of the machine. The main objective of the article is to present the methods of synchronizing a generator of such a design (a rotor with permanent magnets and a starting cage) and their consequences on the behavior of the machine. The presented design allows synchronization of the generator with the network in two ways. The first method enables synchronization of the generator with the power system by asynchronous start-up, i.e., obtaining a starting torque exceeding the braking torque from the magnets. The second method of synchronization is similar to the method used in electromagnetically excited generators, i.e., before connecting, the rotor is accelerated to synchronous speed by means of a water turbine, and then, the machine is connected to the grid by switching on the circuit breaker. This paper presents electromagnetic phenomena occurring in both cases of synchronization and describes the influence of magnet temperature on physical quantities. Full article