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Electric Solar Wind Sails (E-Sails) are a new type of spacecraft propellantless propulsion system that gathers its energy from solar wind protons and is potentially useful for interplanetary missions. Although optimal interplanetary trajectories have been the subject of thorough research, the substantial variability of the solar wind necessitates the adoption of active guidance strategies, an area that has received significantly less scholarly attention. This paper proposes guidance algorithms for E-Sails based on Model Predictive Control (MPC), a modern control methodology based on online re-planning of the trajectory. To this end, first, properties of E-sail time-optimal orbits are studied applying Pontryagin's Minimum Principle, and then time-optimal orbits for missions to Mars and Jupiter are computed via direct transcription methods. Next, solar wind perturbations are modeled, posing a challenging saturation problem due to their high variability. Guidance strategies based on Shrinking Horizon and Receding Horizon Model Predictive Control (RHMPC) are developed, analyzed and compared using Monte Carlo simulations, successfully implementing MPC to E-sail guidance. Lastly, the RHMPC strategy is successfully tested with accurate historical solar wind data from the WSA-Enlil model. • Solar wind fluctuations implies need of guidance in E-sail interplanetary missions. • Optimal planning for E-sails is performed using direct and indirect methods. • Control saturation due to solar wind pressure is reduced by leaving control margins. • Model predictive control guidance methods are compared with Monte Carlo analysis. • Receding horizon strategy in tested with semi-empirical historical solar wind. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) is introduced in systems with electrical machines, such as in electric drive systems, wind energy generating systems, and small and special machines, to remote monitor and control the operation for data acquisition and analysis. These systems can integrate with the equipment and retrofit the existing installations. At the end of the control loops there are always motors, or actuators, of big or small ratings, of rotating or linear movements, electrical or nonelectrical, which must produce the motion. This article analyses selected aspects of research and applications of IoT-based control in electric drive systems and of wind energy conversion systems with induction machines. Various applications and study cases of control systems of electrical machines with IoT technology are described. With the IoT-based control of induction machine systems operators can remotely monitor parameters and obtain accurate real-time feedback during fast changing duty cycle operation. Thus, IoT creates multipurpose instruments in the remote control of induction machines. The paper offers a comprehensive analysis of IoT-based control applications in the field of induction machines, with technical details of design, construction, experimental testing, and prototyping, that are useful to energy engineering specialists in the sector of electric drives and wind energy conversion systems. [ABSTRACT FROM AUTHOR]

• The combination of an electric solar wind sail and an electric thruster is proposed. • A multi-objective optimization algorithm is used to evaluate mission performance. • Circle-to-circle Earth-Mars and Earth-Venus transfers are used as test case scenarios. • A small propellant consumption allows transfer time to be significantly reduced. An electric solar wind sail is a propellantless propulsive system that generates thrust by exploiting the electrostatic interaction between solar wind ions and one or more charged tethers. Assuming a realistic near-term design in which the sail is composed of a limited number of tethers, the propulsive acceleration provided to the spacecraft is small. Moreover, according to a recent thrust model, the propulsive acceleration vector is constrained to lie in a cone centered on the outward radial direction with half-angle equal to about 20 degrees, resulting in a small circumferential component of the propulsive acceleration. In order to overcome these issues, a possible strategy consists in combining the electric sail with an electric thruster that provides a low thrust steerable around the circumferential direction. The effectiveness of such a combination is thoroughly analyzed in this work for deep-space heliocentric transfers. Transfer trajectories are obtained as outputs of a multi-objective optimization procedure, in which a suitable linear function of the flight time and the propellant consumption is minimized, considering different relative weights of the two competing requirements. Two exemplary case studies, consisting of Earth-Mars and Earth-Venus ephemeris-free circle-to-circle transfers, are presented to show the effectiveness of the proposed arrangement. [ABSTRACT FROM AUTHOR]

Research on corona wind generation has been increasing in recent years because of its potential technological applications, particularly those related to improving heat transfer in small-scale devices. Since numerical simulations play a key role in the design of these applications, computationally efficient modeling of corona discharge is imperative. This work presents a new approach that allows rapid computation of the electrohydrodynamic (EHD) force density responsible for the generation of electric wind. Arbitrary electrode configurations can easily be dealt with in the model, since only the Laplacian electric field lines have to be determined numerically. Then, using approximated analytical approximations of the electric field intensity along the field lines, the spatial distribution of the current density and the space charge density can be easily determined. The model has been satisfactorily tested against experimental measurements of the current–voltage characteristic and the current density distribution on the cathode. Furthermore, the electric wind computed from the EHD force agrees quite satisfactorily with measurements carried out in different electrode configurations. Finally, the model has been applied to a new electrode configuration that has greater potential for heat transfer applications. [ABSTRACT FROM AUTHOR]

The electric solar wind sail (E-sail) spacecraft is a fuel-free propulsion system with promising potential in deep space explorations and solar activity monitoring missions. It is challenging to conduct attitude control for a full-scale flexible E-sail spacecraft due to its complex dynamical characteristics, including the spatial multi-scale, high-speed spinning, and large deformations. In this work, a double-loop attitude control strategy for the flexible E-sail spacecraft with high accuracy and efficiency is proposed. The E-sail spacecraft is firstly modeled by the referenced nodal coordinate formulation, where the rotations are described by the Lie group approach. A state-feedback controller developed from the Lyapunov stability theory is prescribed as the inner loop. The gain is obtained by solving a semidefinite programming problem with linear matrix inequality constraints, which is globally optimal and numerically reliable. A multi-variable proportional-integral-derivative controller is then introduced as the outer loop for flexibly enhancing the control performance. Several missions of the E-sail spacecraft, including attitude maneuvers on heliocentric and displaced non-Keplerian orbits, are studied to show that the desired attitude adjustments are accurately and efficiently achieved without exciting high-frequency oscillations. The double-loop control strategy has great prospects in designing and implementing orbital transformation and long-term stable Sun-orbiting missions. • A double-loop attitude control strategy for the full-scale flexible E-sail spacecraft. • The rotation is described by a Lie group approach without singularity. • The Lyapunov stability is adopted to model and calculate the inner loop gain. • The accuracy and adjustability are improved by the multi-variable PID controller. • The strategy is accurate and efficient for displaced non-Keplerian orbit missions. [ABSTRACT FROM AUTHOR]

Serious requirements are put forward for aircraft electric machines (EMs) in terms of weight and size indicators. To reduce the mass of EMs, it is possible to consider aluminum windings, the density of which is 3 times less than that of copper windings. However, due to the much lower electrical conductivity of aluminum (40% less than that of copper), the overall performance of EMs with the same output parameters with aluminum windings is higher. In this regard, there is an interest in the electrical industry in increasing the electrical conductivity of aluminum windings. This problem can theoretically be solved by using carbon nanotubes (CNTs) together with aluminum. This article presents the results of a study of additive windings of aircraft EMs from a powder alloy based on aluminum with CNTs. Visual inspection shows that aluminum windings with CNTs have a 7.4 times more porous structure. The results of experimental studies show that after adding CNTs, the electrical conductivity of aluminum windings became 35% lower and the resistance 50% higher compared to aluminum windings without CNTs. Thus, in the presented work, additive aluminum windings with CNTs exhibit much worse electromagnetic properties compared to aluminum windings without CNTs. [ABSTRACT FROM AUTHOR]

Modern electric machines are attracting great interest from the research community as a result of the increasing number of current applications, including electric vehicles and wind power generators, among others. Different machines, power converters, and control technologies are used, and the number of sensors is usually minimized to reduce the total cost of the system. Particularly interesting are the current and speed sensors, which are essential to the normal functioning of the entire system. This work analyzes different calibration techniques of these sensors, using as a case example a five-phase induction motor drive. Experimental results are included to show the influence of calibration techniques on the system analyzed. The obtained results can be extrapolated to any other similar system. [ABSTRACT FROM AUTHOR]

Based on the predictions of global 3D hybrid simulations, we present a new transport/acceleration path for escaped O+ ions in the upstream solar wind region resulting from the impact of a particular IMF tangential discontinuity (TD) with negative (positive) IMF Bz on the discontinuity's anti‐sunward (sunward) side. For O+ ions escaping to the duskside magnetosheath and with gyro‐radii larger than the TD thickness, when they encounter the TD, they can first go sunward into the upstream solar wind. They then gyrate clockwise to the pre‐noon side and get accelerated within the solar wind region and circulate back to the dawnside magnetosphere. These ions may be accelerated to well within the ring current energy range depending on the solar wind electric field strength. This new transport/acceleration path can bring some of the escaped ions into the inner magnetosphere, thus providing a new mechanism for generating an O+ ring current population. Plain Language Summary: O+ ions in the magnetosphere only come from the Earth's ionosphere. For O+ ions escaping the magnetosphere, scientists have been treating them as being lost. Using simulations that can describe the O+ ion's kinetic dynamics, we find that, due to the impact of a particular solar wind structure, some escaped O+ ions can circulate back to the magnetosphere via a transport path in the upstream solar wind region and some of them can even enter the inner magnetosphere. Additionally, they are also energized by solar wind electric field and thus can contribute to the ring current population. Therefore, this study shows a new journey of escaped O+ ions. Key Points: First global 3D hybrid simulations to investigate the fate of O+ ions after escaping the dayside magnetosphereNew transport/acceleration path for escaped O+ ions in upstream solar wind region after impact of an IMF tangential discontinuityNew transport/acceleration path brings some of escaped O+ ions back to the inner magnetosphere, contributing to O+ ring current pressure [ABSTRACT FROM AUTHOR]

In this study, the force generated by atmospheric positive and negative corona discharges was investigated using a simulation of a wire–cylinder configuration. We provided new insight into the atmospheric corona discharge by introducing a nonlinear force on the charged particles in the vicinity of the wire electrode. To elucidate the origin of both forces in corona discharges, we performed 2D simulations via COMSOL Multiphysics and MATLAB software. It was observed that the direction of nonlinear force is always from the wire to the cylinder regardless of the applied voltage polarity. It was illustrated that the corresponding nonlinear force of the positive corona is larger than that of the negative corona discharge. However, the span of the nonlinear force is greater in the negative corona discharge. The numerical simulation results showed that, in addition to the linear force (Coulomb force), a strong nonlinear force is generated around the wire electrode (powered electrode) that plays a complementary role in the production of electric wind caused by corona discharge. As this nonlinear force is limited to the vicinity of the wire electrode, it is possible to ignore the nonlinear force with a good approximation in the calculation of the total electrohydrodynamic force, but this force cannot be ignored in the process of forming the electric wind. [ABSTRACT FROM AUTHOR]

For a system simulating the dynamics of a single-link electromechanical manipulator, the problem of constructing a control voltage and determining the areas of final states is solved, the transition to any point of which from the initial state of rest using the constructed control occurs in a finite time without violating the specified restrictions on the voltage and heat release power in the winding of the rotor of the electric motor. [ABSTRACT FROM AUTHOR]

The technology of Internet of Things (IoT) can be integrated with systems of electrical machines, for electric drives and wind and solar generation systems, and advance controlling and monitoring. This work presented recent research and progress of electrical drives with IoT technology, regarding design, operation, and trial of the control system for induction motors (ΙΜ). Also, the developed software code and hardware units for speed control were detailed and the results obtained from tests of performance of the ΙΜ integrated with IoT were described. With the IoT integration set-up, the operator can control the frequency values, obtain real-time feedback of the process, and monitor the system during varying loads in steady state. The operation of the ΙΜ system driven by inverter and its monitoring over IoT was proven to have high-accuracy speed control and increased efficiency at supersynchronous speeds. Thus, IoT establishes potentials to become a multipurpose tool in the industrial control of electric drives. This paper established one case study of an IoT set-up and control technique for IM, which is suitable for energy engineering experts in the field of IoT control of industrial equipment. [ABSTRACT FROM AUTHOR]

In micro-grids (MGs), renewable energy resources (RESs) supply a major portion of the consumer demand. The intermittent nature of these RESs and the stochastic characteristics of the loads cause a frequency stabilization issue in MGs. Owing to this, in the present manuscript, the authors try to uncover the frequency stabilization/regulation issue (FRI) in a two-area MG system comprising wind turbines (WTs), an aqua-electrolyzer, a fuel cell, a bio-gas plant, a bio-diesel plant, diesel generation (DG), ship DG, electric vehicles and their energy storage devices, flywheels, and batteries in each control area. With these sources, the assessment of the FRI is carried out using different classical controllers, namely, the integral (I), proportional plus I (PI), and PI plus derivative (PID) controllers. The gain values of these I, PI, and PID controllers are tuned using the recently proposed smell agent optimization (SAO) algorithm. The simulation studies reveal the outstanding performance of the later controller compared with the former ones in view of the minimum settling period and peak amplitude deviations (overshoots and undershoots). The SAO algorithm shows superior convergence behavior when tested against particle swarm optimization and the firefly algorithm. The SAO-PID controller effectively performs in continuously changing and increased demand situations. The SAO-PID controller designed in nominal conditions was found to be insensitive to wide deviations in load demands and WT time constants. [ABSTRACT FROM AUTHOR]

In this paper, a multi-objective allocation and scheduling of wind turbines and electric vehicle parking lots are performed in an IEEE 33-bus radial distribution network to reach the minimum annual costs of power loss, purchased grid energy, wind energy, PHEV energy, battery degradation cost, and network voltage deviations. Decision variables, such as the site and size of wind turbines and electric parking lots in the distribution system, are found using an improved golden jackal optimization (IGJO) algorithm based on Rosenbrock's direct rotational (RDR) strategy. The results showed that the IGJO finds the optimal solution with a lower convergence tolerance and a better (lower) objective function value compared to conventional GJO, the artificial electric field algorithm (AEFA), particle swarm optimization (PSO), and manta ray foraging optimization (MRFO) methods. The results showed that using the proposed method based on the IGJO, the energy loss cost, grid energy cost, and network voltage deviations were reduced by 29.76%, 65.86%, and 18.63%, respectively, compared to the base network. Moreover, the statistical analysis results proved their superiority compared to the conventional GJO, AEFA, PSO, and MRFO algorithms. Moreover, considering vehicles battery degradation costs, the losses cost, grid energy cost, and network voltage deviations have been reduced by 3.28%, 1.07%, and 4.32%, respectively, compared to the case without battery degradation costs. In addition, the results showed that the decrease in electric vehicle availability causes increasing losses for grid energy costs and weakens the network voltage profile, and vice versa. [ABSTRACT FROM AUTHOR]

Due to the high-power density and compact structure, axial-flux permanent magnet (AFPM) machines have gradually received much attention with a view to researching breakthroughs in the next generation electric drive technology for electric vehicles in the recent decades. The AFPM machines with factional slot concentrated winding (FSCW) and yokeless stator, namely yokeless, and segmented armature (YASA) motors, have drawn much attention for its high-power density and potential manufacturability due to the concentrated winding and modular stator core configuration. However, the significant rotor loss resulting from the abundant armature reaction harmonics in FSCW machines imposes a great challenge to the rotor heat dissipation, especially when the pursuit of higher speed has become the trend for electric vehicle applications. On the other hand, distributed winding is widely used in high speed radial flux permanent magnet (PM) machines due to its low armature reaction harmonics. In order to figure out the advantages and disadvantages of various winding arrangement and rotor configuration of AFPM for electric vehicle applications, the comparative study of four AFPM machines with various winding configurations and rotor PM arrangements are comprehensively conducted in this article. First, the design and primary optimization of the four AFPM machines are conducted for the electric vehicle requirement specifications. Then, a comprehensive three-dimensional finite-element analysis (FEA) is employed to compare the electromagnetic performance including torque/power density, efficiency, and flux-weakening capacity. Furthermore, the guideline of winding selection of AFPM machines for electrical vehicle is given. Finally, a yokeless stator AFPM prototype with ISDW configuration is manufactured and tested to verify the validity of the FEA results, as well as confirm the comparison conclusion. [ABSTRACT FROM AUTHOR]

This article is focused on the research concerning the calculation of the durability of electrical machines installed in the electrical system of M-28 and C-130 Hercules aircraft. The article presents a method of predicting the service life of aircraft commutator machines, which are the primary source of electrical energy. The result of the research was the determination of the durability of bearings and coils of electrical machines operated on aircraft based on a flight profile analysis. It is problematic to directly measure the wear of bearings and windings of an electric machine on the aircraft. Their usage can be determined from the relation between their wear and the ambient temperature. This research can be used in practice to plan maintenance work on the analyzed aircrafts. [ABSTRACT FROM AUTHOR]

Purpose: The proposed hybridized framework provides a new performance optimization-based paradigm for analysing the failure behaviour of paneer unit (PU) in the dairy industry. Design/methodology/approach: A novel fuzzy Jaya-based Lambda–Tau Optimization (JBLTO) approach-based mathematical modelling was developed for calculating various reliability indices of the considered unit. Failure mode and effect analysis (FMEA) was carried using qualitative information gathered from system's expert opinions. Fuzzy-complex proportional assessment (FCOPRAS) approach was integrated within FMEA to recognize the most critical failure causes associated with various subsystem/components. Findings: The availability of the unit falls by 0.053% as the uncertainty level increases from ±15 to ±25% and further decreases to 0.323% as the uncertainty level increases from ±25 to ±60%. Failure causes, namely wearing in gears of gearbox (MST4), an impeller's cavitation and/or corrosion (CFP4), winding failure of electric motor (WS9), were recognized as the most critical failure causes with FCOPRAS final performance scores of 100, 100 and 100 and fuzzy combinative distance-based assessment (FCODAS) resultant assessment score of 0.5997, 1.1898 and 1.6135. Originality/value: JBLTO approach-based reliability results were compared with traditional particle swarm optimization-based Lambda–Tau (PSOBLT) and traditional fuzzy Lambda–Tau (FLT) approaches for confirming the downward trend in the system's availability. The ranking results of qualitative analysis are compared with the implementation of FCODAS technique. Sensitivity analysis was executed to evaluate the robustness of the proposed hybridized framework. [ABSTRACT FROM AUTHOR]

The presented article concerns issues related to the diagnostics of the technical condition of the insulation of electrical machines. It discusses the importance of the operational supervision, maintenance and diagnostics of electrical machine insulation systems. The structure of the insulation system is presented and known solutions for making winding insulation are described. The negative impact of conditions and various exposures on the technical condition of the insulation system is described. Special attention is focused on the review of available diagnostic methods for insulating systems of electrical machines. These methods have been arranged in a systematic order according to the type of tests to be carried out. [ABSTRACT FROM AUTHOR]

Electricity generation with minimal environmental pollution is required for the world's sustainable future, and wind electric generation is one of them. Brushless doubly fed induction generator (BDFIG), which derives from cascade induction machine technology, has grown in popularity as a wind electric generator due to advantages over doubly fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) such as the absence of slip rings and brushes and high-cost permanent magnets. Wind energy research is critical for any country's economic development and long-term sustainability. As a result, an experimental setup in a laboratory is required to replicate the behaviour of a wind turbine in the steady state. This study discusses the emulation of wind turbine characteristics in the laboratory using a prototype of a separately excited DC motor mechanically coupled to a brushless doubly fed induction generator (BDFIG). The wind turbine emulator-brushless doubly fed induction machine (WTE-BDFIM) prototype was tested in the laboratory under high power and low wind speed conditions. As a result, the simulation of the same hardware configuration in MATLAB was performed to investigate the overall performance of the BDFIM-based WECS. To determine the equivalent circuit parameters of the BDFIM, which are required for simulation, tests were performed on a prototype of 3.5 kW, 2/6 pole, 400 V, star/delta-star, and BDFIM in two modes, namely, the simple induction mode and the cascade induction mode. Based on the BDFIM parameters, a MATLAB Simulink model of a BDFIG-based wind electric conversion system (WECS) is created and its performance is investigated. Results of both hardware and simulation show that BDFIG can be used as the wind electric generator over a wider speed range compared to that of DFIG, an important feature that is required to get maximum power extraction from the wind turbine. [ABSTRACT FROM AUTHOR]

In this letter, an internal electric field shielding layer for high voltage winding of medium voltage high frequency transformer used in a modular cascaded medium voltage solid state transformer is proposed. Without breaking the litz wire insulation layer, the high electric field is effectively shielded by a semiconducting layer and an unclosed copper foil spiral, which are electrically connected together. Not only the electric field in the main wall insulation is uniformed but also the peak value of the internal field is greatly reduced, which will help to achieve lower partial discharge and higher insulation reliability. With this structure, the difficulties of pouring process and electric field estimation for the litz wire winding are both avoid. Finally, a no partial discharge 100 kW medium voltage high frequency transformer prototype with 75 kV base insulation level is built and verified with the insulation tests. [ABSTRACT FROM AUTHOR]

This paper presents a comparison of an AC radial flux interior permanent magnet (IPM) motor with the distributed winding (DW) and concentrated winding (CW). From time to time, manufacturers of electric vehicles change the design of electric motors, such changes may include changing the DW into CW and vice versa. A change to the winding in a radial permanent magnet synchronous motor may lead to a change in motor parameters during motor operation and /or change in the distribution of the magnetic field and thermal circuit of the electrical machine. The electromagnetic analysis, efficiency map, mechanical stress, and thermal analysis of the machine with the DW and CW are presented in this paper. This article describes the advantages and disadvantages of selected stator winding designs and helps understand manufacturers' designers how the DW and CW play a key role in achieving the designed motor's operational parameters such as continuous performance. Analyzing the performance of both machines will help identify their advantages and disadvantages with regard to thermal phenomena, magnetic field and operational parameters of the presented IPM prototypes. Both prototypes are based on commonly used topologies such as 12/8 (slot/pole) and 30/8 (slot/pole) IPM motors consisting of magnets arranged in a V-shape. The AC IPM motor was designed for an 80 kW propulsion system to achieve 170 N·m at a base speed of 4 500 rpm. Modern CAD tools are utilized throughout the numerical computations based on 2-D finite element methods. Selected test data are used to verify and validate the accuracy of finite element models. [ABSTRACT FROM AUTHOR]

Existing studies about the harmonic analysis of grid-connected converters (GCCs) mainly focus on the frequency range below Nyquist sampling frequency (NSF) or switching frequency (SF) to make full use of linearization. However, in some actual high-power industrial applications; e.g., electric railways or wind power generation, harmonic problems are challenging in a wide frequency that can be as high as thousands of hertz. This is much higher than the NSF and SF. In order to bridge the gap, this article extends the harmonic analysis frequency to the entire frequency range by addressing the aliasing effect and sideband effect. These two effects can be neglected at the low frequency for simplification while they will make great differences at the high frequency, as demonstrated in this article, due to the frequency coupling and nonlinear characteristics. In this regard, a regression method based on an artificial neural network is used to map the in–out relation of the pulsewidth modulation process. By adopting the methodology of this article, harmonic performances of GCCs can be analyzed comprehensively and explicitly in terms of harmonic instability, harmonic resonance, harmonic overvoltage, filter design, and so on. Finally, experiments are presented to verify the effectiveness and accuracy of the analysis. [ABSTRACT FROM AUTHOR]

The humidity role in the partial discharge (PD) inception mechanism is quite complex, and there is no widely accepted theory that can describe the humidity effect on PD. In this article, the PD activity of interturn insulation of electric motor winding is experimentally investigated for different relative humidity (RH) conditions at 30 °C ambient temperature. Since the inception of PD leads to a boost in the dissipation factor (i.e., tan $\delta$) and insulation capacitance (IC), tan $\delta $ and IC tip-up test can be adopted as an indirect measurement of PD. The test campaign is carried out employing twisted pairs as samples, and both tan $\delta $ and IC are measured under a sinusoidal voltage regime. Apart from being indirectly detected, PD activities are also directly measured through a photomultiplier, while the tip-up test is performed. The adoption of direct PD measurement is to discriminate the PD from other ionization processes (e.g., water film ionization), which cannot be distinguished by indirect measurement. The experimental findings allow stating that the change of PD inception voltage (PDIV) at higher RH is due to the different places of water film formation on the insulation surface, and Paschen’s law combined with finite element analysis is used to interpret the effect of water film on PDIV. In addition, it is verified that the tan $\delta $ and IC tip-up test is not suitable for indirect measurement of PD in high humidity conditions. In fact, the higher leakage current, due to the water condensation on the insulation surface, influences the tan $\delta $ and IC measurements causing an increment in their values regardless of the PD inception. [ABSTRACT FROM AUTHOR]

This work is devoted to the formulation of innovative SCADA-based methods for wind turbine performance analysis and interpretation. The work is organized as an academia–industry collaboration: three test cases are analyzed, two with hydraulic pitch control (Vestas V90 and V100) and one with electric pitch control (Senvion MM92). The investigation is based on the method of bins, on a polynomial regression applied to operation curves that have never been analyzed in detail in the literature before, and on correlation and causality analysis. A key point is the analysis of measurement channels related to the blade pitch control and to the rotor: pitch manifold pressure, pitch piston traveled distance and tower vibrations for the hydraulic pitch wind turbines, and blade pitch current for the electric pitch wind turbines. The main result of this study is that cases of noticeable under-performance are observed for the hydraulic pitch wind turbines, which are associated with pitch pressure decrease in time for one case and to suspected rotor unbalance for another case. On the other way round, the behavior of the rotational speed and blade pitch curves is homogeneous and stable for the wind turbines electrically controlled. Summarizing, the evidence collected in this work identifies the hydraulic pitch as a sensible component of the wind turbine that should be monitored cautiously because it is likely associated with performance decline with age. [ABSTRACT FROM AUTHOR]

A very simple and therefore wide-spread way to control motor speed and torque is to regulate the stator voltage by pulsewidth modulation (PWM). Depending on the modulation type, number of inverter levels, and modulation index of the PWM, various spectral components occur in the supply signal and inject ripple current in the motor phases. This current distortion can cause significant additional losses in the stator and rotor core, permanent magnets, and windings of an electric machine. Therefore, it is important to consider these losses in an early design stage. In this work, an efficient calculation method for harmonics of multilevel PWM signals and generated phase currents with different modulation types is presented. The PWM losses are calculated via 2-D finite element method analyses. The calculation and simulation workflow is realized within the software tool SyMSpace and applied to a three-phase permanent magnetic synchronous machine (PMSM). Loss measurements at different PWM frequencies and load points are conducted on a 3-phase PMSM. Since simulation and measurement results show good accordance, the proposed methods could be validated. [ABSTRACT FROM AUTHOR]

Spoke-array brushless dual-electrical-port dual-mechanical-port (SA-DEP-DMP) machine is a good candidate for continuously variable transmission device, because of its high compactness, contactless torque transmission, and decoupled rotors. Due to the specific features, including two independent controllable rotors, two set windings, and complex magnetic field coupling, some unique design considerations of SA-DEP-DMP machine are analyzed in this article. First, there is a little accurate analytical model for DEP-DMP machine. An applicable analytical model is proposed to directly describe the characteristic of air-gap magnetic field and calculate the sizing equation. The key innovation is that the inner air-gap permeance with the slot effect is mapped into the magnetic potential by air-gap mapping model, which simplifies the double air-gap structure into a single air-gap structure. Second, the torques of two rotors are always optimized separately at the same time. Using this design method, the optimal torques of two rotors cannot achieve simultaneously for many parameters. In order to solve this problem, a novel constant torque ratio design method is proposed where two windings electric loading distributions are considered. The influences of key parameters, such as combination of slot and pole, stator split ratio, permanent magnet size, etc., on the torque performances are analyzed based on finite-element analysis. Finally, an SA-DEP-DMP prototype is manufactured. [ABSTRACT FROM AUTHOR]

A method is proposed for determining the number of damaged stator windings in the presence of an asymmetric power supply system for an induction electric motor based on the Park vector hodograph. As a result of the experiments on the simulation model, it was found that with the symmetry of the system of supply voltages and stator windings, the hodograph of the Park vector describes a circle; in all other cases it is an ellipse. It has been established that the presence of asymmetry in the supply voltage system is indicated by the angle of inclination of the ellipse, and the indicator of the presence of the asymmetry of the stator windings is the angle of ellipticity. In order to identify the presence of asymmetry of the stator windings in the conditions of asymmetry of the supply voltage system, an algorithm for recalculating the ellipse parameters for the condition of the symmetry of the supply voltage system was proposed. Recalculation errors did not exceed 6%. It has been established that the dependence of the increment of the amplitudes of the phase and angles of the phase currents of the stator on the number of damaged turns of the stator winding is linear. Based on this fact, an algorithm for determining the number of damaged turns was proposed. The results of this work can be used to build systems for diagnosing the interturn short circuit of the stator of an induction electric motor built into the drive. [ABSTRACT FROM AUTHOR]

An electric solar wind sail (electric sail or E-sail) is a new type of propulsion system that does not require propellant. This paper proposes a nonlinear model predictive control law based on deep learning to control the attitude of a barbell electric sail. A barbell E-sail is composed of two tip satellites connected via long conductive tethers to a central insulated confluence point. The two tethers are insulated from each other at the confluence point such that the voltages of the two tethers can be independently controlled. The attitude dynamics of the system is modelled using a nonsingular description of tether orientation. To reduce online computation loads, the proposed control scheme has a two-stage design, namely, an offline stage and an online stage. In the offline stage, a large amount of data is generated using the nonlinear model predictive control law and then taken as a dataset to train a deep neural network. In the online stage, feedback control of the system attitude is achieved with extremely low computational cost by performing real-time mapping from the system state to the control output using the trained deep neural network. Finally, the efficacy and performance of the proposed deep learning-based control law are demonstrated via numerical case studies. • Attitude dynamics of an E-sail system is modelled by a nonsingular formulation. • Nonlinear dynamics and inherent constraints of the system are accounted for. • Extremely low computational cost of feedback control is achieved using a DNN. [ABSTRACT FROM AUTHOR]

Summary: Renewable energy resources have a remarkable landmark across the world to provide electricity to the consumers without any inadequacy in the energy market. The utilization of renewable energy sources in electric vehicle charging stations is among the most prominent area of research in developing countries. This paper analyses techno‐economic and environmental factors of hybrid solar wind vehicle charging stations at the highway of Southern Tamil Nadu, India. The sensitivity analysis is performed in the design of a charging station at the following highway locations at Madurai, Virudhunagar, Sattur, Kayathar, and Tirunelveli. The locations are chosen in such a way that, wind and solar potentials are having contradictory nature in the specified locations. The charging station is designed and optimized as ON‐grid strategy using the hybrid optimization model for electrical renewable tool. The designed system is capable of charging 17 electric vehicles at day from forenoon 6:00 am to evening 6:00 am The attainment of the proposed designed system proves that Virudhunagar shows less net present cost with $303 291.26 and cost of energy as $0.072/kWh with 50% reduction in emission. Moreover, with a focus on economic analysis and Madurai produces 70% more electrical energy than other selected locations. Further, the performance analysis of the system is also studied and it shows more reliable results and is feasible considering both economic and technical studies. [ABSTRACT FROM AUTHOR]

The main insulation structure of the valve‐side winding of converter transformer bears the effect of AC and DC superimposed voltage during operation. The electric field intensity in the pressboard is much higher than that in the pressboard in the AC transformer. This condition increases the probability of failure of insulation structure. Therefore, the design and optimization of the main insulation structure of the valve‐side winding are keys to ensure the stable operation of converter transformer. This study establishes a model of the main insulation structure of the valve‐side winding of the ±1100 kV converter transformer. The influence of the insulating oil–paper configuration on the electric field distribution of the main insulation structure of the valve‐side winding is analysed, and then, an optimization idea is proposed. The oil–paper configuration includes two aspects: oil–paper insulation structural design and combination selection, that is, the influence of typical oil–paper structural design parameters and the aging state of different oil–paper combinations on the electric field distribution. Finally, the optimization idea of the oil–paper configuration for valve‐side winding of converter transformer is obtained, and the established model is optimized. [ABSTRACT FROM AUTHOR]

This research analyzes the techniques involved in basic winding in relation to anthropometric characteristics of subjects. The first aim of this study was to determine whether there is a statistically significant difference between the subjects in the technique of performing basic curvature in relation to their anthropometric characteristics. The second aim of this study was to determine the difference in the technique of primary windings in relation to anthropometric characteristics of subjects. In a sample of 30 students, average age 22 years, male, measuring by 12 anthropometric measures and a situational-motor test was carried out. Alpine skiing technique was assessed through primary windings, the technical element of skiing which is present in the basic form of skiing. Based on the performance of the basic curvature and the obtained results, three subsamples of respondents were defined as "weak", "moderate" and "good". Between the treated subsamples, differences in anthropometric characteristics were established and clearly defined limits in the degree of adoption of the basic winding technique. The subsample defined as "weak" has less pronounced measures of longitudinal and transverse dimensionality, volume and body weight and moderately has pronounced skin folds of the upper arm and back, more pronounced length of the lower leg. The subsample defined as "moderate" has less pronounced skin folds and moderately expressed the length of the lower leg, the circumference of the upper leg and the diameter of the knee. Body height, shoulder width, skin fold of the abdomen, body weight, arm length, medium chest circumference and pelvic width are more pronounced. The subsample defined as "good" has a less pronounced knee length and medium chest circumference and has a moderately pronounced body height, shoulder width, skin fold of the abdomen, body weight, arm length and pelvic width. It has more pronounced skin folds of the upper arm and back, as well as the circumference of the upper leg and the diameter of the knee. Based on these results, we can conclude that, the differences are established and boundaries are clearly defined in the level of adoption of the basic winding techniques between subsamples in relation to anthropometric characteristics. [ABSTRACT FROM AUTHOR]

Due to the dual air‐gap topology of the direct‐drive permanent magnet motor with inner enhance force (IEF‐DDPMM), the radial EM exciting force generated in the inner and outer air gaps when the rotor is eccentric will act on the same rotor, and the unbalanced magnetic pull (UMP) on the rotor will reduce the fatigue life of the rotor structure and bring many problems such as vibration and noise. Therefore, the rotor UMP compensation method of IEF‐DDPMM based on modular winding d‐axis current injection is proposed to suppress the harm caused by eccentricity. The expression of electromagnetic (EM) exciting force considering the cogging effect and current time harmonic without rotor eccentricity faults is derived by the analytical method. Also, the EM exciting force newly introduced due to the rotor eccentricity is analysed. The effects of different eccentricity types on torque characteristics, the fatigue life of the rotor structure and stator vibration of IEF‐DDPMM are compared and analysed by the FEM. Finally, the IEF‐DDPMM rotor eccentricity models are optimised based on the method. The performance of the motor before and after rotor UMP compensation is evaluated by FEM. The results show that the proposed method is correct and effective. [ABSTRACT FROM AUTHOR]

Controlling the highest temperature in the windings is the primary objective of transformer thermal design to guarantee designed transformer thermal life expectancy. Temperature rise test results of a transformer with computational fluid dynamics (CFD) modelling results are compared here to determine typical OD and ON flow rates in the transformer. It then presents CFD studies that compare the thermal behaviour of two types of disc‐type windings. The S disc‐type winding refers to one that has only axial cooling ducts and physically resembles a layer‐type winding. The other type is of conventional disc‐type winding. The S disc‐type winding shows robust thermal performance due to its quasi‐uniform flow distributions in the axial cooling ducts, irrespective of the total oil flow rates or the cooling modes. In contrast, the conventional disc‐type windings converted from the S disc‐type winding experience uneven flow distributions in the radial cooling ducts that can cause localised overheating. Control of oil flow distribution in conventional disc‐type windings is found critical for its thermal design. Heat transfer for the S disc‐type winding is further enhanced by axially partitioning the winding into multiple sections, which is optimized based on theoretical analyses and is then verified by CFD modelling. [ABSTRACT FROM AUTHOR]

The noise and vibration level in modular‐type permanent magnet synchronous machines with fractional slot concentrated windings (FSCW) is considered to be an important design consideration, particularly for applications requiring fault tolerance. In this work, an interior permanent magnet synchronous machine (IPMSM) with FSCW is designed in a modular manner by dividing its stator windings into different arrangements having independent three‐phase sub‐modules with separate neutral points. First, the modular concentrated winding arrangement is studied to investigate the radial forces, vibration, and the associated noise level in the prototype machine having three‐phase sub‐modules under open‐circuit fault conditions. Then, another type of distributed three‐phase sub‐module winding arrangement is analysed to further investigate the vibration and noise level in the same prototype machine under the same operating conditions. A detailed two‐dimensional (2D) fast Fourier transform analysis is performed to investigate and compare the machine radial forces, induced harmonics, and sub‐harmonics for the two analysed winding arrangements. Considering the advantages and disadvantages of both the winding arrangements, the third type of mixed concentrated and distributed three‐phase sub‐modules winding arrangement is introduced in this work, combining the first two winding design approaches. A comprehensive harmonic (3D) structure, along with the vibration and noise analysis, is performed using a multi‐physics model analysis for all the winding arrangements under different three‐phase sub‐modules open‐circuit fault conditions. Lastly, the vibration levels of all the machine prototype models under different winding arrangements are experimentally validated. Moreover, the different modular types of winding arrangements are deeply investigated in this work to suggest the best winding arrangement approach that enables the machine to work in a wide range of applications requiring lower power levels or under critical, faulty, and hostile conditions. The proposed winding arrangement has reduced stator deformation with a reduced vibration and noise level under three‐phase sub‐modules open‐circuit fault‐tolerant conditions that can be used according to process requirements. [ABSTRACT FROM AUTHOR]

Dual windings parallel (DWP) coils are often used in high‐power wireless charging applications to reduce current stress and internal resistance. Due to the inconsistent self‐inductance and strong coupling of the two windings, the advantages of the DWP coils cannot be fully utilized. In particular, the current stresses of the two windings are different, which will cause one of the stress to exceed the limit, and the temperature rise is too high. The reason for the current imbalance in the two windings is analysed in this work, and a distributed capacitor compensation method is proposed to balance the current stress in the two windings. Finally, a WPT system with the DWP transmitting coil was built as an example to demonstrate the effectiveness of the proposed method. The experimental results show that the current ratio in two windings decreased from 1.70 to 1.05 after using the proposed compensation method. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation is a unique environment allowing for making non-contact measurements over samples of liquid metals at different temperatures. The electromagnetic coil is the core of the electromagnetic levitation system, and its design defines the amount of energy introduced into the sample as well as the shape and stability of the latter during levitation. In the present work, analytical and numerical modelling for a real electromagnetic inductor is performed and compared with experimental observations. The shape of the experimental electromagnetic coil is assured due to 3D printing of a template which is used for the coil winding. [ABSTRACT FROM AUTHOR]

Within the CERMISO INCDMTM Bucharest center, the study of drones requires, among other processing equipment, the use of a high-volume industrial plastic 3D printer. This is the reason why the center was equipped with a JCR 1000 Dual printer with a 1000 x 600 x 600 mm printing volume (insulated and heat-controlled), two printheads, closed enclosure and heatcontrolled bed. In the period of about two years since the acquisition of this industrial equipment, we have performed tests, trials and research on this model of 3D printer, so we have reached a series of problems that can be solves for a more safe and precise operation. The problems and the related solutions found are presented in this paper. There are 5 sensitive areas that affect working with this equipment: a. Calibration of the printing bed in 49 points; b. ABS and PLA wire aging too fast inside the equipment driving pipes; c. Loss of reference during printing in case of the appearance of voltage spikes and transients; d. Problems of total job loss due to power failure; Given our rich experience with such printers, the paper will present a number of viable solutions to these problems. These proposals are made in such a way as to require a minimum of investment and effort. [ABSTRACT FROM AUTHOR]

The three‐phase permanent magnet synchronous motor (three‐phase PMSM) has gained much popularity in many applications due to its various advantages. In addition, due to the good fault tolerance, simple inverter circuit structure and high torque density, the six‐phase PMSM has better prospects than three‐phase PMSM in biomedical devices, electric vehicles and other fields with high reliability requirements. In this study, a six‐phase axial‐flux PMSM inherently without cogging torque is proposed to improve torque density, which equips the 60° phase‐belt toroidal winding (60°TW) and slotless stator core. Based on the same effective volume, permanent magnet material, power grade and the other major motor parameters, two six‐phase PMSMs with 30° phase‐belt toroidal winding (30°TW) and 60°TW are designed, respectively. The armature reaction field, air gap magnetic density, back‐electromotive force, output torque, loss characteristic and torque‐speed characteristic are compared by using three‐dimensional (3D) finite‐element models in detail. Finally, the experimental test is carried out using the prototype of three‐phase PMSM with 120° phase‐belt toroidal winding. The experimental results indirectly verify the feasibility of 60° phase‐belt toroidal winding and correctness of 3D FEM. The 3D FEM analysis results are presented to show that torque density of the proposed six‐phase PMSM with 60°TW is improved in comparison to the six‐phase PMSM with 30°TW. Index Terms—60° phase‐belt toroidal winding, axial flux, six‐phase permanent magnet synchronous motor, torque density [ABSTRACT FROM AUTHOR]

Assessment of solar and solar wind parameters driving the ionosphere model is essential for prediction of the ionospheric weather. In the present paper impact of the different solar, interplanetary and geomagnetic parameters on the global electron content (GEC) during intense space weather storms is investigated. Hourly GEC values are calculated from JPL global maps of total electron content GIM-TEC from 1995 to 2023. The sample comprises 90 intense storms from 1995 to 2023 associated with monthly peak of the weighted accumulation of the geomagnetic Apo (τ, t) index exceeding 90 nT. The 27 day weighted accumulation of the solar sunspot numbers SSN2 (τ), solar radio flux F10.7 (τ), the solar hydrogen emission Lyman _ α (τ) and the composite magnesium MgII (τ) indices are explored as precursors of GEC enhancements. As distinct from the positive ionosphere storm, the solar wind speed Vsw , the solar wind electric field Ey , merging electric field Em and Apo (τ, t) indices proved to be effective as potential drivers of the negative GEC depletion. The positive and negative dGEC deviations from hourly GEC are produced by subtracting a quiet reference GECav averaged during 24h prior the storm normalized by GECav. The hourly storm profiles Vsw(t) , Em(t) , Ey(t) , Apo (τ, t), Dst(t) , GEC(t) and dGEC(t) were reduced by method of superposed epochs. The zero epoch t 0 = 0 was taken at the peak Apo* (τ, t 0) and the storm time lasted for 48h from −12h prior t 0 and 35h afterwards. The best correlation of the positive storm dGECp amplitude is obtained with MgII (τ) and the negative storm dGECn with E m * and Apo* (τ, t 0) which are used to derive characteristics of five key points of storm-time dGEC (t) model: 1 – onset of the storm profile t 1 = t(dGECp) ; 2 – the amplitude dGECp max and its time t 2 (dGECp max); 3 – the time of transition t 3 (dGEC = 0) from the positive to negative (±) GEC storm; 4 – minimum negative disturbance dGECn min and its time t 4 (dGECn min), 5 – the end of the storm profile t 5 (dGECn). Analytical model of dGEC (t) is derived with Epstein step functions fitting 5 key points. Deviations dGEC (t) are inverted to GEC (t) using quiet reference pre-storm GECav. The model is validated for three intense storms on 26–28 February, 23–25 March and 23–25 April 2023. The results show improvement of dGEC forecast with RMS error reduced from 45 to 80% compared to results produced by the international reference ionosphere−plasmasphere model IRI-Plas. • Accumulation SSN2(τ), F10.7(τ), Lyman-α(τ), MgII(τ) show the best correlation of MgII(τ) with positive GEC storm. • Sample 90 intense storms for 1995–2023 are reduced by superposing with zero epoch at Apo (τ, t) > 90 nT. • Solar wind merging electric field Em proved to be the best precursor for Apo (τ , t), Dst(t) and negative GEC storm. • dGEC (t) forecasting model with MGII (τ) and Em field precursors shows RMSE improved by 45–80% compared to IRI-Plas. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) as Dysprosium (Dy) are critical elements for the fabrication of components in many green energy technologies, from electric vehicles to wind turbines. Consequently, there is an increasing interest in creating sustainable and effective materials for the recovery and recycling of these elements. Zeolite materials have demonstrated a high affinity and selectivity for REEs. Thus, this paper aims to study the use of a synthetic LTA zeolite functionalized with nanomagnetite for Dy absorption, including a complete characterization of the synthetic zeolite, the kinetics and the factors affecting the adsorption efficiency. The maximum adsorption capacity reaches a value around 35 mg of Dy per gram of zeolite. The results from the adsorption isotherms and kinetic study revealed a good agreement with both Langmuir and Temkin models and pseudo-second-order kinetics. Furthermore, the thermodynamic analysis suggests that the adsorption of Dy onto the zeolite is a spontaneous and favorable process. The findings from this work could provide insights into the design and optimization of zeolite-based processes for REE recovery and recycling, contributing to the development of a more sustainable and circular economy. [Display omitted] • LTA zeolite functionalized with nanomagnetite was obtained by hydrothermal method. • Characterization confirms morphology, structure and functionalization of the zeolite. • Zeolite was employed to recover dysprosium through an adsorption process. • The maximum adsorption capacity of the zeolite for Dy was approximately 35 mg g−1 • Functionalization allows for easy separation from liquid solution with a magnet. [ABSTRACT FROM AUTHOR]

The article discusses the problem of determining electrical parameters of superconducting coils with bare windings. Procedures for measuring these parameters are described; in particular, inductance was measured by the voltage of a linear current input at a given rate. Although it is demonstrated to be impossible to determine inductance in a winding with a bare superconductor in the normal state, the inductance of a winding is comparable to that of an insulated wire in a superconducting state at currents below the critical value. The results of measuring the inductance, radial resistance, static current-voltage and magnetic characteristics of two tape coils with bare superconducting windings, one of which had a soldered connection, are presented. The insulated and bare superconducting winding parameters were compared and measurement conditions for the latter were formulated. The results of the study are applicable to the design and operation of superconducting devices with bare windings, such as coils, magnetic storage devices, stator windings of electric machines, etc. [ABSTRACT FROM AUTHOR]

This paper investigates the spin rate bounds, the configuration stability subject to the solar wind fluctuations, and sail angle control of an electric solar wind sail (E-sail) by a high-fidelity tether dynamic model. This model describes the elastic deformation of tethers with inter-connected 2-noded tensile elements discretized by the nodal position finite element method. The E-sail is assumed to be an axisymmetric system spinning in the plane normal to the heliocentric ecliptic plane. The upper and lower spin rate bounds are revisited to reveal the physics that dictates these bounds and analytic expressions are provided to ensure the proper operation of E-sail. Then, the influences of the solar wind fluctuations on the configuration stability of the E-sail are investigated by parametric analysis with different E-sail configurations, sail angles, and spin rates. Finally, an alternative sail angle control strategy for the E-sail is proposed by applying control force at the remote units with a simple PD control. Numerical analysis demonstrates that the sail angle of E-sail can be controlled quickly by the control law at the remote units with a high-precision. • Derived a new theoretical lower bound of spin rate for E-sail with auxiliary tethers. • Analyzed structural dynamics of E-sail by a high-fidelity tether dynamic model. • Revealed necessity and effectiveness of auxiliary tethers by tether dynamic perspective. • Controlled sail angle by applying control forces at remote units only. [ABSTRACT FROM AUTHOR]

Operation of Vernier machines is based on flux modulation. They have some advantages including maintaining the rated torque in motor applications and the rated output power in generator applications at low speeds, high torque density and relatively low torque ripple due to their magnetic gear property and fault‐tolerance. In recent years, the motor with various topologies has been developed for different applications. Therefore, analysing and monitoring different faults is essential in the design and implementation stages. This study has two main purposes. First, to introduce an accurate frequency index independent of load variations for detecting the turn‐to‐turn short circuit (TTSC) faults in the stator windings of a permanent magnet Vernier machine. Second, modelling the machine in a healthy condition and in the presence of TTSC faults to investigate its effect on machine performance and output characteristics. An analytical model is presented using the modified winding function theory under the TTSC fault by taking into account the effect of stator slots which enhances the accuracy of the air‐gap permeance function estimation. In the process of calculating the fault index, frequency components of the output characteristics of the machine are obtained from the mathematical equations of the magnetic field. It is shown that the proposed indicators are robust against load variations. [ABSTRACT FROM AUTHOR]

Observations of spiders’ pre-dispersal behavior can be used to answer various ecological and evolutionary questions. So far, dispersal experiments have often used air currents as a stimulating factor. Effects of electric fields on the pre-dispersal behavior of spiders have recently been discovered. Electric fields may lead to unexplained variation in results and limit comparability between previous studies. Here we aim to disentangle the roles of wind and electric fields on the passive aerial dispersal of three linyphiid spider species. Our results confirm that strong electric fields in the air elicit predispersal behavior, and in combination with a light wind, facilitate dispersal (take-off). Nevertheless, even the strong electric fields employed here played a rather supplementary role in spiders’ dispersal with wind remaining the most influential factor. We recommend that studies of passive aerial dispersal should control for electric field strength but otherwise use wind as the primary stimulating factor. [ABSTRACT FROM AUTHOR]

Direct cooling of the windings in a motor using oil offers more effective thermal management than conventional alternatives and can therefore increase the torque density of electric machines; however, this technique is limited by the thermophysical properties of the oil. The use of a direct winding heat exchanger allows a glycol-water coolant mixture to be used, which leads to a significant improvement in heat transfer and a reduction in the pumping losses compared to direct oil cooling. This article proposes ceramic 3-D printed direct winding heat exchangers (3D-DWHX), which can significantly improve the cooling of windings in electric machines due to the unique geometries enabled by 3-D printing. Ceramics are also capable of withstanding extremely high temperatures, which extends the application of the proposed 3D-DWHX. A closed-form analytical thermal model incorporating the temperature dependence of winding losses is proposed and used with empirical heat transfer correlations to design a microfeature enhanced 3D-DWHX. The ceramic 3D-DWHX was built and tested in a motorette that demonstrated a continuous current density of 35.7 ARMS/mm2, corresponding to a continuous specific power in the reference electric machine of at least 12.1 kW/kg while keeping the maximum winding temperature below 200 °C. [ABSTRACT FROM AUTHOR]

More-electric-aircrafts (MEAs) are heading towards larger power, higher voltage, and more optimum architectures, it is extremely important to understand partial discharge (PD) behaviors under the challenging aeronautical power systems. PD under the pressure of 1–101 kPa and frequency of 50–1000 Hz is studied to emulate the practical situation with the consideration of insulation defects from electric machine windings. The high frequency current transformer (HFCT) is specifically employed to pick up partial discharge signals. Experimental results indicate that PD inception voltage (PDIV) decreases almost linearly with air pressure. As to the discharge amplitude, it increases first and then decreases as air pressure dropping. The highest discharge repetition rate and the number of discharges appear at 30 kPa. High frequency doubles the number of discharges without affecting PD amplitude. Low air pressure causes the phase shift and phase width of the phase-resolved partial discharge (PRPD) to increase, and the trend also is accelerated by high frequency. This experimental approach is beneficial to provide prerequisite knowledge in characterizing PD and assessing its potential adverse impact on the aeronautical power system and consequently contribute to optimizing the insulation design for MEA. [ABSTRACT FROM AUTHOR]

Observations of spiders' pre-dispersal behavior can be used to answer various ecological and evolutionary questions. So far, dispersal experiments have often used air currents as a stimulating factor. Effects of electric fields on the pre-dispersal behavior of spiders have recently been discovered. Electric fields may lead to unexplained variation in results and limit comparability between previous studies. Here we aim to disentangle the roles of wind and electric fields on the passive aerial dispersal of three linyphiid spider species. Our results confirm that strong electric fields in the air elicit pre-dispersal behavior, and in combination with a light wind, facilitate dispersal (take-off). Nevertheless, even the strong electric fields employed here played a rather supplementary role in spiders' dispersal with wind remaining the most influential factor. We recommend that studies of passive aerial dispersal should control for electric field strength but otherwise use wind as the primary stimulating factor. [ABSTRACT FROM AUTHOR]

The electric solar wind sail (E-sail) has been proposed as a novel propulsion system that, if successful, promises to facilitate missions that would be inconvenient or impractical with traditional chemical propellants. The most common E-sail concept includes a central hub with several long positively charged tethers extending radially outward that harvest momentum from protons in the solar wind. Before the technology is ready for a demonstration mission, we must prove E-sail dynamics can be controlled throughout all phases of the mission. The objective of this paper is to present an analytical model for the linear vibrations of hub and spoke E-sails to facilitate the development of necessary control schemes. Although there is no limit to the number of spokes in our model, we demonstrate its capability by representing a system with 3 spokes. The resultant natural frequencies and mode shapes provide insight into the dynamics and stability of E-sails and lay the foundation for development of control schemes. In addition, our work reveals several simple calculations that accurately estimate many of the natural frequencies and could be used to facilitate the design of future E-sails. • Derivation of an analytical model for electric solar wind sail vibrations. • Simple models accurately predict natural frequencies of electric solar wind sails. • Hub and spoke electric solar wind sails can configured to be infinitesimally stable. [ABSTRACT FROM AUTHOR]