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A method of predicting the residual breakdown electrical field strength of an epoxy-mica paper insulation system is described. This method was developed by using data on service?aged stator bars from generators as well as accelerated aging model bars. Thermal aging, mechanical aging, and combined thermal and mechanical aging were done individually as accelerated aging. The partial discharge characteristics, dissipation factor, and breakdown voltage were measured on the model bars and service?aged bars from generators. From these results, the residual breakdown electrical field strength was predicted based on the partial discharge characteristics and dissipation factor. First, the dominant type of deterioration (thermal or mechanical aging) on a bar?s insulation was determined by the pattern of voltage?partial discharge magnitude characteristics. Then the residual breakdown electrical field strength was predicted by using a predicting equation for both thermal and mechanical aging. Each predicting equation uses dissipation factor tip-up (i.e. difference in dissipation factor values between 2 kV and rated voltage) and partial discharge inception electrical field strength. The accuracy of this method was confirmed using data measured on 112 service-aged stator bars from generators and 10 accelerated aged model bars. The 95% confidence interval level included 94% of the measured residual breakdown electrical field strength values. This result shows that the method enables precise predictions of the residual breakdown electrical field strength of an epoxy-mica paper insulation system. [ABSTRACT FROM AUTHOR]

An energy study was performed at Pulpa Cuba Paper Mill, located in Sancti Spiritus, where an energy management system was applied according to NC: ISO 50001, in order to assess the energy system by applying energy management systems for energy and water reduction in the paper mill, in which the current steam generation, distribution and consumption system is diagnosed. The proposal of a modified energy scheme with 1 MW Backpressure Steam Turbine Generator and rehabilitation of the original boiler or installing a lower capacity boiler contributes to save financial resources by the concept of water, fuel and electricity. The implementation of four projects will save 3,095,574 CUC / y and an average payback period of about 1 year is expected. [ABSTRACT FROM AUTHOR]

Sheet tension control is crucial in the paper winding process in order to get properly formed shipping roll(s) produced in the winder. Typically, the tension loop uses load cells as tension sensors, which are expensive and require frequent maintenance and calibration. This paper develops two new tension estimators for a two-drum electric-braking-generator production winder, based on unwinding and rewinding variables, respectively. The estimators consider all the essential dynamic, friction, and inertial variation effects. Both estimators are evaluated in typical trapezoidal winder operating cycles. Multiple sensitivity analyses show that the proposed estimators are robust to normal parameter variations, and give stable and precise sheet tension control without the use of load cell tension loops. [ABSTRACT FROM AUTHOR]

In this letter, we present a ZnO nanogenerator built on a paper substrate producing electricity using both contact electrification and piezoelectric effects. Paper is an environmentally friendly material and can help to improve the performance of the ZnO nanogenerator due to its natural roughness. The nanogenerator produced a maximum peak voltag of 38.4 V and a maximum peak current density of 3.2 \mu \textA /cm ^2 from both the inherent piezoelectric property of ZnO and contact electrification between poly(methyl methacrylate) and ZnO nanostructures. [2014-0388] [ABSTRACT FROM AUTHOR]

In this work, we design and fabricate a wireless system with the main operating device based on zinc oxide (ZnO) nanowires. The main operating device is based on piezoelectric nanogenerator (NG) achieved using ZnO nanowires grown hydrothermally on paper substrate. The fabricated NG is capable of harvesting ambient mechanical energy from various kinds of human motion, e.g., footsteps. The harvested electric output has been used to serve as a self-powered pressure sensor. Without any storage device, the signal from a single footstep has successfully triggered a wireless sensor node circuit. This study demonstrates the feasibility of using ZnO nanowire piezoelectric NG as a low-frequency self-powered sensor, with potential applications in wireless sensor networks. [ABSTRACT FROM AUTHOR]

High power density generators and motors are envisaged in modern all-electric ships where electrical power for both propulsion and service loads is provided through a common electrical platform known as an integrated power system. Three recent high-power density technologies for generators and motors proposed for marine applications are reviewed, and the author focuses on their electrical insulation challenges. These technologies are high-frequency (high-speed) generators (200–400 Hz), superconducting generators, and novel insulation materials and systems. For high-speed generators, high loss in magnetic materials may shorten its insulation life. Thus, these generators should be designed to be cooled by water instead of air. For superconducting generators, the most significant concern is the integrity of the insulation system over the large thermal excursion whenever the system is cycled between room temperature and operating temperature. In novel insulation materials and systems section: (i) using mica paper tapes containing boron nitride filler in the binding resin of the glass backing insulation, developed by Toshiba and Von Roll, resulted in a 15% increase in the MVA of generators for the same slot dimensions and operating temperatures, (ii) GE developed an enhanced polyethylene glycol terephthalate-mica tape having superior voltage-endurance characteristics, (iii) Isovolta has introduced a mica paper tape using a flat glass fibre backing material, called Powerfab, rather than the more common woven structure, leading to a 15% reduced mica tape, and (iv) adding novel nanocomposites as fillers to ground wall insulation, introduced by Siemens, is a promising technique towards more high power density designs. Furthermore, accelerated aging of insulation systems especially those in electrical rotating machines exposed to voltage pluses with high slew rates up to hundreds of kV/μs and high-repetition rates ranging from hundreds of kHz to MHz is discussed. These voltage pulses are generated by wide bandgap-based converters envisaged in the medium voltage DC architecture for future U.S. naval ships.

This paper is based on modifications implemented in the protection and grounding systems of a large paper mill and describes selective ground fault protection for a 13.8-kV system with multiple bus-connected generators, synchronous bus ties, and utility interconnections. The ground fault current in the system is reduced from the existing 3400 A to 500 A, and a hybrid grounding system is implemented for each of the generators. As the ground fault currents are reduced to limit the fault damage, the sensitivity and selectivity of the ground fault protection become important. Directional ground fault relays with coordinating pickup settings are applied to achieve this objective. The new platform for directional elements (numerical relays) drives its performance from sequence impedance measurements. [ABSTRACT FROM AUTHOR]

Previous examinations of fully convective M-dwarf stars have highlighted enhanced rates of nanoflare activity on these distant stellar sources. However, the specific role the convective boundary, which is believed to be present for spectral types earlier than M2.5V, plays on the observed nanoflare rates is not yet known. Here, we utilize a combination of statistical and Fourier techniques to examine M-dwarf stellar lightcurves that lie on either side of the convective boundary. We find that fully convective M2.5V (and later subtypes) stars have greatly enhanced nanoflare rates compared with their pre-dynamo mode-transition counterparts. Specifically, we derive a flaring power-law index in the region of 3.00 ± 0.20, alongside a decay timescale of 200 ± 100 s for M2.5V and M3V stars, matching those seen in prior observations of similar stellar subtypes. Interestingly, M4V stars exhibit longer decay timescales of 450 ± 50 s, along with an increased power-law index of 3.10 ± 0.18, suggesting an interplay between the rate of nanoflare occurrence and the intrinsic plasma parameters, e.g., the underlying Lundquist number. In contrast, partially convective (i.e., earlier subtypes from M0V to M2V) M-dwarf stars exhibit very weak nanoflare activity, which is not easily identifiable using statistical or Fourier techniques. This suggests that fully convective stellar atmospheres favor small-scale magnetic reconnection, leading to implications for the flare-energy budgets of these stars. Understanding why small-scale reconnection is enhanced in fully convective atmospheres may help solve questions relating to the dynamo behavior of these stellar sources. [ABSTRACT FROM AUTHOR]

The main objective of the paper is to demonstrate the functionality and reliability of a hydrokinetic turbine system -- a submersible electric generator, suitable for very low watercourses. To achieve this goal, it is necessary to design and build a prototype of a hydrokinetic turbine, coupled with an electric generator with excitation made with permanent magnets. This paper presents an analytical model and a finite element numerical model for estimating the electrical parameters of the generator (voltage, current, power, etc.). The two models were compared, and the results were extrapolated, in the analytical model, for several speed values. [ABSTRACT FROM AUTHOR]

Examines the installation of an integrated turbine-generator control system for a British Columbian pulp mill. Background of Northwood Pulp Mill of Canadian Forest Product Ltd.; Project objectives; Project implementation; Conclusion.

Maintaining stability in modern power systems is challenging due to complex structures, rising power demand, and load disturbances. The integration of renewable energy sources further threatens stability by causing imbalances between generation and demand. Conventional load frequency stabilization methods fall short in such scenarios. This paper proposes an optimal fractional‐order proportional‐integral‐derivative‐acceleration (FOPIDA) controller, enhanced by a robust adaptive neuro‐fuzzy inference system (ANFIS), to improve load frequency control and reliability in power systems with wind and solar generators. First, the dynamical model of a multi‐area interconnected power system, including a thermal power plant, wind turbine, and solar photovoltaic generators, is developed. A decentralized ANFIS‐FOPIDA controller is then designed for load frequency control objectives. The gains of this controller are optimized using the whale optimization algorithm (WOA), focusing on frequency deviation and tie‐line power exchange. Simulations on a New England IEEE 10‐generator 39‐bus power system demonstrate the approach's effectiveness under various disturbances, including random load‐generation disturbances and nonlinear generation behaviors. Comparisons with other strategies, such as fractional order (FO) beetle swarm optimization algorithm (FOBSOA)‐FOPIDA, WOA‐PIDA, and WOA‐ANFIS‐PIDA, and recent control approaches highlight the superior performance of the WOA‐ANFIS‐FOPIDA method in enhancing power system stability. [ABSTRACT FROM AUTHOR]

Because of the large number of parameters that interact in amplifier functions, determining dynamic regime parameters as well as the mode of function of amplifier stages is an extremely complex problem. This paper describes a LabVIEW application for studying the functioning of an amplifier in various connections. The user selects the generator's parameters, the type of connection and its parameters, as well as the load circuit characteristics. The application can determine both the stage characteristics and the Bode characteristics. The amplifier's stability zone, as well as its gain and phase, are determined based on these characteristics. An important advantage of this application is that the design of the amplifier stage can be created starting from some parameters that the amplifier can establish, from which the values of components can be determined. In order to validate the simulation results from the LabVIEW application, the specialized program Multisim was used, as well as experimental measurements using the Electronics Explorer Board. Both Multisim and Electronics Explorer Board can determine Bode characteristics. In both simulations and experimental amplifiers, the same schemes with the same transistor were used. The application can be used for educational purposes as well as to design an amplifier's stage to achieve specific parameters. [ABSTRACT FROM AUTHOR]

At present, HTS magnets cannot operate in the real closed-loop persistent current mode due to the existence of joint resistance, flux creep, and AC loss of the HTS tape. Instead of using a current source, HTS flux pumps are capable of injecting flux into closed HTS magnets without electrical contact. This paper presents a practical superconducting DC dynamo for charging a conduction-cooled HTS magnet system based on a flux-pumping technique. To minimize heat losses, the rotor is driven by a servo motor mounted outside the vacuum dewar by utilizing magnetic fluid dynamic sealing. Different parameters, such as air gap and rotating speed, have been tested to investigate the best pumping effect, and finally, it successfully powers a 27.3 mH HTS non-insulated double-pancake coil to the current of 54.2 A within 76 min. As a low-cost and compact substitute for the traditional current source, the realization of a contactless DC power supply can significantly improve the flexibility and mobility of the HTS magnet system and could be of great significance for the technological innovation of future HTS magnets used in offshore wind turbines, biomedical, aerospace, etc. [ABSTRACT FROM AUTHOR]

Wind turbine generators in a windfarm are connected by underground cables. Lightning sometimes strikes a nacelle or a blade. Lightning overvoltages due to a direct lightning strike to the system cause damages in the underground cable. Many parameters should be investigated to establish a rational lightning protection design for wind power generation system. Numerical simulation is a useful method to discuss the influence of the parameters on the lightning overvoltages. This paper uses an Electro-Magnetic Transients Program for the lightning surge analysis. This paper discusses the influence of grounding method of metallic sheath of the cable and grounding resistance on the lightning overvoltages for the direct lightning strike to the generation system. [ABSTRACT FROM AUTHOR]

Considering the negative resistance effect of power electronic equipment, unstable resonance problems may occur between wind farms and converter stations. This paper focuses on the resonance stability problem of a wind power base coupling with a multi-level converter−high-voltage direct-current transmission (MMC–HVDC) system. Firstly, the s-domain impedance models of the doubly-fed induction wind generator, the permanent magnet synchronous wind generator, and the modular MMC are built, through the theoretical derivation and simulation test. Secondly, based on the s-domain nodal admittance matrix method, the resonance structure of the wind power base coupling with an MMC–HVDC system is analysed, including the resonance mode frequencies, the resonance mode damping factors, the nodal participation factors, and the nodal voltage mode shapes. Thirdly, the main factors influencing the resonance structure are studied, including the topology of the wind power base, the capacity of the wind turbines, and the operation mode of the MMC station. Finally, a brief conclusion ends the paper. [ABSTRACT FROM AUTHOR]

The efficiency of hybrid electric vehicles may be substantially increased if the energy of exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered using a properly designed turbo-generator and employed for vehicle propulsion. Previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% employing a 20 kW turbine on a 100 HP-rated power thermal unit. The innovative thermal unit proposed here is composed of a supercharged engine endowed with a properly designed turbo-generator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In this two-part work, the realistic efficiency of the innovative thermal unit for hybrid vehicles is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors presented a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, thanks to some assumptions and approximations, allows fast determination of the right turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine here considered is quite different from the ones commonly employed for turbocharging applications; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In this paper, Part 2, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantages that could be achieved by the implementation of the turbo-generator on a hybrid propulsion system are evaluated through the performance prediction model under different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbo-compound system could gain vehicle efficiency improvement between 3.1% and 17.9%, according to the output power delivered, with an average efficiency increment of 10.9% evaluated on the whole operating range. [ABSTRACT FROM AUTHOR]

High Temperature Superconducting (HTS) dynamo flux pumps are a promising alternative to metal current leads for energization and the persistent current mode operation of high current DC superconducting magnet systems for applications in rotating machines, such as Magnetic Resonance Imaging (MRI) or fusion systems. The viability of the flux pump concept has been widely proven by laboratory experiments and research is now in progress for the design and optimization of flux pump devices for practical applications. It has been widely established that the dependence of the critical current density (Jc) on the temperature (T), the magnetic field magnitude (B), and the orientation (θ), has a substantial impact on the overall DC voltage obtained at the terminals, as well as on the current limit and the loss of the flux pump. Since HTS tapes produced by different manufacturers, they show different dependencies of Jc with the amplitude and the orientation of the magnetic field. They also give rise to different outputs when employed in flux pumps. In this paper, we evaluate and compare the performance of several commercial HTS tapes used for flux pumping purposes through numerical simulation. We also investigate the dependence of the flux pump 's performance on the operating temperatures. A 2D finite element numerical model is first developed and validated against experimental data at 77 K. Afterward, the same HTS dynamo apparatus used for validation is exploited for the comparison. The Jc(B,θ,T) and n (B,θ,T) relations, which characterize each different tape in the model, are reconstructed via artificial intelligence techniques based on the open-access database of the Robinson Research Institute. It is shown in the paper that certain tapes are more suitable than others for flux pump applications and that the best overall operating temperature is in the vicinity of 77 K. [ABSTRACT FROM AUTHOR]

In this paper, we extend Shaposhnikov et al.'s parity violating the Einstein–Cartan–Holst action by adding to Holst term H, a Proca photon–torsion coupling χpt = 10−24 as computed by De Sabbata, Garcia de Andrade, and Sivaram. The strength of Holst term is obtained, in the case of early universe torsion as, T ∼ 1 MeV. The gravity part is the Planck mass product with the Holst term. The photon mass in this case yields m2γH ∼ 10−69 GeV4. Therefore, in this case, the photon interacts very weakly with spin-torsion matter in Einstein–Cartan (EC) gravity and the strength of the Maxwell–Proca–Holst interaction is much weaker than in the pure gravity sector. For dark photons, this situation changes drastically since a dark photon mass reaches 1.5 GeV, and from this mass and T = 10−3 GeV, one obtains a Maxwell–Proca–Holst strength of 10−6 GeV4, which is now comparable with the gravity sector. Dynamo mechanism competes with the chirality and dissipation by the handness of the magnetic field with respect to the torsion trace vector to regenerate the magnetic field decay. Bombacigno and Mantovani recently found a sign of the Immirzi parameter in the Holst–Nieh–Yan extension of EC gravity. Here, we also find torsion waves for the Immirzi inverse parameter in the sense that this divergence of torsion trace is porportional to the Immirzi field. [ABSTRACT FROM AUTHOR]

Multi-layer metamodeling is a metamodeling method that provides great flexibility for domain prototyping, while it also ensures rigid validation of domain rules. Visualization of multi-layer models would be essential in order to promote this new modeling technique in industrial setups; however, the traditional way of representing model entities is not sufficient here. Dynamic Multi-Layer Algebra is a multi-layer metamodeling approach that addressed the challenges of multi-layer modeling, but uses a text-based language to create models. This paper presents Dynamo, a visual notation for Dynamic Multi-Layer Algebra, which is also applicable to other multi-layer metamodeling approaches. The paper elaborates the graphical syntax and the design decisions. [ABSTRACT FROM AUTHOR]

The flywheel-type dual-stator permanent magnet starter generator combines engine flywheel and starter generator rotor into a single unit, which has the advantages of high efficiency, high power density, and compact structure. This paper proposes a new type of dual-stator permanent magnet starter generator topology in which the two stators are concentric and share the same permanent magnet rotor. Equivalent magnetic circuit modeling of the inner stator's magnetic field, outer stator's magnetic field, and synthetic magnetic field using the equivalent magnetic circuit method list the system of flux equations and solve the main magnetic flux, leakage flux, and leakage coefficient, and the results show that the equivalent magnetic circuit method has smaller error and higher accuracy than the finite element method. The harmonic electric potential of the starter generator is modeled and analyzed. The permanent magnet rotor and inner and outer stator structures are optimized to obtain the optimal parameters, and the prototype is manufactured and tested. The optimized starter generator no-load induced electromotive force fundamental amplitude is improved. The induced electromotive force harmonic distortion rate is reduced, and the output performance of the whole generator is significantly improved. [ABSTRACT FROM AUTHOR]

After long-term operation of a generator, the stator winding will gradually experience aging or electrical corrosion, and scientific experimental analysis methods are needed to diagnose the health status of equipment. By analyzing the leakage current data of stator winding DC withstand voltage tests of multiple large tubular generators, this paper proposed an insulation performance evaluation method and measures to prevent winding breakdown; according to the electrical corrosion and high operating temperature of stator winding of wall mounted structure, we studied a series of innovative designs and processes for stator renovation, and conducted finite element simulation calculation of stator temperature field. The temperature rise test data shows that the operating temperature of the generator after stator modification is effectively reduced, and there is significant reduction in temperature deviation at each measuring point. The research results are close to the simulation calculation values, proving that the new process adopted for stator transformation is effective and feasible. [ABSTRACT FROM AUTHOR]

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This paper provides a proof of concept for a linear electric generator that can be used to harvest energy from various sources of linear motion, such as vibrations, free-piston engines and wave energy. The generator can be used to power small electronic devices, such as sensors, or charge household batteries. The literature was reviewed to develop an understanding about the applications, control methods, excitation methods and mechanics of rotating and linear electric machines. A bidirectional, two-sided linear machine was designed with two stator cores and a single mover core. The stator windings and mover winding can be independently excited, allowing for three modes: no mover excitation, a DC excited mover, and an AC excited mover. Simulation results showed that the magnetic flux generated by DC excited stator cores were concentrated in the centre of the mover core. The use of two stator cores eliminates lateral flux in the mover core when it is not excited, minimising attraction and repulsion forces. Parametric analysis showed that flux cutting occurred in all operation modes, verifying that the generator will produce power when operating. Hardware tests produced an output current when the machine was electrically and mechanically excited, verifying the proposed design. [ABSTRACT FROM AUTHOR]

The rise of the renewable energy sources (RES) in microgrids has increased the impact of damping and low inertia on network stability. This gives rise to several issues in the power systems, including power fluctuations from variable RES, degradation of the frequency regulation, voltage surges, and oversupply from grid‐connected distributed generators. This paper presents a cascaded hybrid load‐frequency controller for an airport microgrid that addresses frequency fluctuations caused by load changes. It is combining a self‐adaptive fuzzy controller (SAF) and a classical two‐degree‐of‐freedom proportional integral derivative (PID) controller (2DOFPID) called CSAF‐2DOFPID. It is applied to the control section of a diesel generator, an electric aircraft energy storage system, and a demand response program. The controller parameters are optimized using a suggested hybrid differential artificial hummingbird algorithm (D‐AHA) to minimize frequency deviation. The proposed control framework is simulated on an airport microgrid comprising various components, and the impact of time delay on the controller's signals, system uncertainty is also examined. The simulation results demonstrate that the proposed self‐adaptive cascaded fuzzy controller outperforms other controllers such as PID, CF‐PID, and CF‐2DOFPID in reducing frequency fluctuations, and the D‐AHA algorithm achieves favourable results compared to other algorithms in the optimal tuning controller parameters. [ABSTRACT FROM AUTHOR]

The Covid-19 pandemic has resulted in a permanent shift in individuals' daily routines and driving behaviours, leading to an increase in remote work. There has also been an independent and parallel rise in the adoption of solar photovoltaic (PV) panels, electrical storage systems, and electric vehicles (EVs). With remote work, EVs are spending longer periods at home. This offers a chance to reduce EV charging demands on the grid by directly charging EV batteries with solar energy during daylight. Additionally, if bidirectional charging is supported, EVs can serve as a backup energy source day and night. Such an approach fundamentally alters domestic load profiles and boosts the profitability of residential power systems. However, the lack of publicly available post-Covid EV usage datasets has made it difficult to study the impact of recent commuting patterns shifts on EV charging. This paper, therefore, presents SPAGHETTI (Synthetic Patterns & Activity Generator for Home-Energy & Tomorrow's Transportation Investigation), a tool that can be used for the synthetic generation of realistic EV drive cycles. It takes as input EV user commuting patterns, allowing for personalised modeling of EV usage. It is based on a thorough literature survey on post-Covid work-from-home (WFH) patterns. SPAGHETTI can be used by the scientific community to conduct further research on the large-scale adoption of EVs and their integration into domestic microgrids. As an example of its utility, we study the dependence of EV charge state and EV charging distributions on the degree of working from home and find that there is, indeed, a significant impact of WFH patterns on these critical parameters. [ABSTRACT FROM AUTHOR]

Significant changes have occurred in the protection and grounding of generators in the past 15 years that impact generators at petroleum refineries and chemical plants. This paper updates the author's earlier paper on the subject of generator protection upgrades and highlights areas of protection that are still not addressed by some generator owners, as well as new protection areas not previously addressed. New generator protection changes are reflected in recent IEEE guides such as C37.102-2006. This paper discusses these changes as they apply to industrial generators and the risks of ignoring them. This paper outlines the risks in several functional areas where old generator electromechanical relay protection is inadequate. In addition, this paper discusses hybrid grounding of the generator stator windings, which substantially reduces stator ground fault damage—avoiding lengthy generator outages to repair. This type of grounding is a relatively new concept in generator grounding introduced in a series of IEEE Industry Applications Society (IAS) Working Group papers publicized in 2002. This grounding scheme has been installed on a number of generators but must be coupled with proper relaying and transient overvoltage protection. This paper also highlights the major new protection requirements for gas turbine starting with a load commutating inverter and protection advances made possible by the use of digital technology, which have fostered new methods not possible with older technologies. [ABSTRACT FROM AUTHOR]

In this paper, dual-rotor counter-rotating (CR) configurations of vertical axis wind turbines (VAWTs) are briefly inspected and divided into three types. This investigation was focused on one of these types—the CR-VAWT with co-axial rotors, in which two equal rotors are placed on the same shaft, displaced from each other along it and rotated in opposite directions. For this CR-VAWT with three-blade H-Darrieus rotors, the properties of the design in terms of aerodynamics, mechanical transmission and electric generator, as well as control system, are analyzed. A new direct-driven dual-rotor permanent magnet synchronous generator was proposed, in which two built-in low-power PM electric machines have been added. They perform two functions—starting-up and overclocking of the rotors to the angular velocity at which the lifting force of the blades is generated, and stabilizing the CR-VAWT work as wind gusts act on the two rotors. Detailed in this paper is the evaluation of the aerodynamic performance of the CR-VAWT via 3D computational fluid dynamics simulations. The evaluation was conducted using the CONVERGE CFD software with the inclusion of the actuator line model for the rotor aerodynamics, which significantly reduces the computational effort. Obtained results show that both rotors, while they rotate in opposite directions, had a positive impact on each other. At the optimal distance between the rotors of 0.3 from a rotor height, the power coefficients of the upper and lower rotors in the CR-VAWT increased, respectively, by 5.5% and 13.3% simultaneously with some increase in their optimal tip-speed ratio compared to the single-rotor VAWT. [ABSTRACT FROM AUTHOR]

Renewable energy sources, which use natural sources to generate energy, are currently replacing conventional energy sources to fulfil the world's expanding energy demands. However, photovoltaic and wind energy, which are among these types of energy sources, are not steady and not available for 24 hours in a day. As an alternative, it is possible to extract and use hot water from the earth all the time. Therefore, this study proposes a thermoelectric generator that uses hot water from the hot spring area to generate free electricity as a new renewable energy source in a microgrid application. In this system, the microgrid is standalone without a battery storage system because the thermoelectric generator is in operation for 24 hours in a day (day and night). In this way, the cost of the battery is eliminated by removing it from the system. In this paper, a novel generation method is proposed in microgrid applications as a renewable energy source. In addition, load management system was implemented to control three types of residence loads. The main advantage of this study is to generate electricity from renewable sources like photovoltaic and thermoelectric to demand without much wasting energy by controlled loads according to the proposed load management algorithm. In this study, the microgrid and energy management control is modeled with MATLAB/Simulink. The results showed that the essential load is always active through thermos electric generator besides the absence of battery storage system. [ABSTRACT FROM AUTHOR]

As the main insulation of high-voltage motors, the poor mechanical and thermal conductivities of mica paper restrict the motor's technological advances. This paper prepared multilayer toughening mica composites with a highly ordered "brick-mud" stacking structure by mimicking the natural conch nacre structure. We investigated the mechanical, thermal, and breakdown properties by combined study of tensile strength, stiffness, thermal conductivity, and breakdown strength at varying mica and nanocellulose contents. The results show that thermal conductivity of the mica/chitosan composites were gradually enhanced with the increase in mica content and the composite shows the optimal synthetic performance at 50 wt% mica content. Further addition of the nanocellulose can extremely enhance the thermal conductivities of mica/chitosan composites. The composite with 5 wt% nanocellulose obtained the maximal thermal conductivity of 0.71 W/(m·K), which was about 1.7 times that of the mica/chitosan composite (0.42 W/(m·K)) and much higher than normal mica tape (0.20 W/(m·K)). Meanwhile, the breakdown strength and tensile strength of mica/chitosan/nanocellulose composite also demonstrated substantial improvement. The application of the mica/chitosan/nanocellulose composite is expected to essentially enhance the stator power density and heat dissipation ability of large-capacity generators and HV electric motors. [ABSTRACT FROM AUTHOR]

The nature and causes of corrosive sulfur induced failures are examined in oil-filled transformers and shunt reactors. Copper sulfide, which is formed when the corrosive sulfur in a mineral oil reacts with the copper conductors, is likely to diffuse into the paper tapes insulating the conductors. Since copper sulfide is partially conducting, the dielectric losses of the contaminated oil-impregnated-paper tapes are markedly increased; paper tapes in close proximity to the copper conductors are found to attain tan 5 values > 1.0 even at room temperature. It is highly likely that thermal instabilities develop at those sites at operating temperatures, leading to increased loss currents and, ultimately, short circuits between the turns. This sequence of events is substantiated by evidence from the field, which indicates large areas of thermally degraded insulations and charred breakdown regions along the coils, the extent of which becomes more pronounced at higher operating temperatures (toward the top of the windings). [ABSTRACT FROM AUTHOR]

This article provides a comprehensive overview of the performance evaluation of looped tube thermoacoustic power generators using numerical and experimental analysis. The study focuses on small-scale generators operating at atmospheric pressure and utilizing low-cost linear alternators. The analysis considers factors such as temperature variation, pressure fluctuation, volume flow rate, and acoustic power distribution. The results show that the generators produce maximum acoustic power at a frequency of 78 Hz, with an overall thermal to electric efficiency of approximately 8.3%. The article also includes references to other research papers and articles that cover various aspects of thermoacoustic engines and generators, providing valuable insights into the field. [Extracted from the article]

A study on the possibility of integrating a micro-turbogenerator system into a multi-rotor UAV platform was performed along with a performance evaluation of the result. This paper presents the design and development of a micro-turbogenerator system constructed from commercially available components and the associated test bench that was needed to validate the system. The goal of the micro-turbogenerator system was to replace the electrical power source (the batteries) of an experimental UAV. Substituting the electrical power source with a hybrid propulsion system has the potential to enhance the UAV's endurance and functionality, rendering it more versatile and efficient. The hybrid propulsion system involves the use of a commercially available micro-gas turbine that propels an electric generator, supplying the required electrical power for the UAV's electric propulsion system. Integrating this micro-turbogenerator system ensures a substantial increase in UAV endurance. The test bench was used to assess the performance of the micro-turbogenerator system and formulate a control law necessary for maintaining a balance between the power generated by the system and the power consumed by the UAV. The developed test bench yielded crucial data, including electric power, generated voltage, generator speed, and power consumption (simulating the UAV in this case). During the testing campaign, the variation in the main physical quantities involved in the command and control of the hybrid propulsion system was registered and analyzed. A total power of 700 W was obtained during the tests, which is the maximum that can be registered for maintaining a power of 25 V. [ABSTRACT FROM AUTHOR]

Linear permanent magnet vernier generators offer a high capability of force density, making them appealing configurations for wave energy harvesting systems. In absolute terms, the performance of these machines is significantly influenced by the selection of slot/pole combinations based on the magnetic gearing effect. For the first time, this paper aims to investigate the impact of different gear ratios on a wide array of linear primary permanent magnet vernier machines (LPPMVMs) with different slot/pole combinations based on fair criteria to offer a more comprehensive understanding of gear ratio selection. To find the optimal number of slots and poles, the response surface methodology is adopted to obtain a robust design and make a fair comparison among LPPMVMs with optimum design characteristics using a cost‐effective approach for the fast and reliable optimisation process. The higher gear ratios result in higher thrust force capability. This will help establishing a new route toward faster develpment of advanced LPPMVMs. The power loss models of LPPMVMs are studied to predict their steady‐state and transient thermal behaviours, verifying their stability and safety, while a simple external forced convection method can be utilised. To verify the model, finite element analysis is exploited to confirm the electromagnetic and thermal analysis results and provide a more exhaustive investigation. [ABSTRACT FROM AUTHOR]

The nonlinear modeling and analyzing of wound-rotor synchronous starter/generators (WRSSGs) plays a vital role in the analysis and monitoring of aircraft power systems. Moreover, they are of great significance with regard to the establishment of a future aircraft smart grid. However, owing to its nonlinear, high-dimensional, and strong coupling characteristics, this modeling has always remained in the frequency domain stage and the progress of more intuitive time domain modeling has been slow. This paper presents a nonlinear model of a WRSSG in a generating state. When the WRSSG is in power generation mode, most cases indicate that the aircraft is in flight mode. The establishment of the nonlinear model of the system in the power generation state is of great significance for the research of the health management and state monitoring of the aircraft power system and can improve the safety and reliability of the aircraft during flight. The model uses FE analysis and neural network to solve the nonlinear problem of the motor in the system and uses the improved variable parameter average model to solve the nonlinear problem of the rotating rectifier. According to the principle of signal transmission, a time domain model for the whole system is developed. Finally, the model is compiled by the RT-LAB real-time simulator. The nonlinear model performs well when compared with FE analysis results and tested against the MIL-STD-704F standard. The proposed nonlinear model and analysis results can be used for the condition monitoring and fault diagnosis of aircraft power systems. The hardware-in-the-loop test platform based on an accurate nonlinear model is a feasible means to study the failure of expensive equipment, and it can aid the study of irreversible failures of equipment at a low cost. [ABSTRACT FROM AUTHOR]

The increasing demand for electricity and the need for environmentally friendly transportation systems has resulted in the proliferation of solar photovoltaic (PV) generators and electric vehicle (EV) charging within the low voltage (LV) distribution network. This high penetration of PV and EV charging can cause power quality challenges, hence the need for hosting capacity (HC) studies to estimate the maximum allowable connections. Although studies and reviews are abundant on the HC of PV and EV charging available in the literature, there is a lack of reviews on HC studies that cover both PV and EVs together. This paper fills this research gap by providing a detailed review of five commonly used methods for quantifying HC including deterministic, time series, stochastic, optimization, and streamlined methods. This paper comprehensively reviews the HC concept, methods, and tools, covering both PV and EV charging based on a survey of state-of-the-art literature published within the last five years (2017–2022). Voltage magnitude, thermal limit, and loading of lines, cables, and transformers are the main performance indices considered in most HC studies. [ABSTRACT FROM AUTHOR]

Vault modelling in HBIM poses a significant challenge due to the geometrical complexity and lack of standardization of those elements. Starting from the definition of an ontology able to describe and manage different typologies of Italian Renaissance vaults, this paper presents two methods for their representation in the context of Ducal Palace of Urbino HBIM implementation. The first method is a simplified semi-automated scan-to-BIM procedure relying on Revit adaptive families; the second is a more complex parametric scripting in Dynamo VPL. The paper proposes a library of suitable vault families for the parametric modelling of Renaissance architecture and offers a comparison between the models generated and their respective surveyed point-clouds, with the aim of assessing the procedure. Revit adaptive families appeared to be the easiest to implement and the most efficient solution, while Dynamo allowed for greatest complexity thought showing limitations and implementation difficulties. [ABSTRACT FROM AUTHOR]

The present paper is part of a larger project whose purpose is to develop a new hydrokinetic turbine-generator assembly, suitable for very low head water courses. It presents the experimental results of a turbine--generator physical model, installed on the tailrace of Mihailesti Hydropower Plant. In order to carry out the measurements, a floating structure and an anchoring system was installed on the power plant tailrace. This system also allowed the translation of the assembly between the two shores. A first set of measurements followed the water velocity and depth in the channel at various load values of the hydropower plant units, in order to determine the proper conditions for testing the model. The turbine gives the possibility of blades adjustment at three different angles, 0, 9 and 14 degrees respectively. Therefore, a set of measurements has been performed for each position of the blades. The measured parameters were the electric parameters of the generator such as voltage, current and the power variation with rotation speed. For the blades adjustment of 9 degrees and 1.76 m/s water velocity, the generator reached its maximum power of 500 W. The results retrieved will be used for the optimization and design of a new enlarged scale turbine--generator assembly. They will also be used as input data for the numerical modeling of the generator. Also, the exact knowledge of the channel geometry and flow parameters is valuable in studies preceding testing a prototype in the site. [ABSTRACT FROM AUTHOR]

Multichannel digital sinewave generators play a key role in digital automated impedance bridges. Along with the technological progress in the development of commercial data acquisition (DAQ) boards, which brings with it improvements in their metrological and functional properties, it is possible to realize the DAQ-based high-precision multichannel generators. This paper describes the evaluation of properties of three commercial DAQs, available in the form of PCI eXtensions for Instrumentation modules and working as two-channel generators supervised by software developed by the authors. Due to the fact that the main application area of these generators is digital impedance bridges, this paper presents research results the most relevant for the impedance bridges, i.e., the stability of amplitude ratio and phase difference as well as total harmonic distortion and spurious-free dynamic range. The results and conclusion presented in this paper may be useful when choosing DAQs intended to be used in the multichannel generators. [ABSTRACT FROM AUTHOR]

This paper proposes a control-oriented energy function (COEF) based on passivity for transient stability control (TSC) of power systems and investigates the feasibility of an iterative process using the COEF for determining generation shedding (GS) requirements for real-time TSC, in particular, for severe cases when autoreclosing fails due to permanent faults. The COEF for TSC set up in this paper gives directly the GS requirement without calculations of stability region and Critical Clearing Time, and exempts all modeling assumptions except for nonnegative damping the generator models. The simulation with the full planning model of Western Electricity Coordinating Council system shows that the passivity-based COEF for TSC offers a concise, practical, and effective index for GS determination for transient stability control of power systems, which is particularly suitable for the Remedial Action Schemes that BC Hydro has been using. [ABSTRACT FROM AUTHOR]

This paper presents the results of the experiment with an overmassed wire-array $Z$ -pinch load that is powered by a current pulse (amplitude ~4.3 MA and rise time $\sim 0.9~\mu \text{s}$) from a multidisk magnetocumulative generator. Interesting feature of the experimentally recorded soft X-ray (SXR) pulse is short (~10 ns) duration at a microsecond current rise time with total energy of several hundreds of kilojoules. Obtained results are the evidence of high-quality implosion of the current-carrying plasma. The 2-D magnetohydrodynamic code FLUX-rz was used for the numerical simulation and analysis of the obtained results. The calculations indicated that only ~30% of the initial load mass took part in the SXR generation. The main peculiarities of the overmassed $Z$ -pinch implosion are discussed in this paper. [ABSTRACT FROM AUTHOR]

Astrophysical jets are launched from strongly magnetized systems that host an accretion disk surrounding a central object. Here we address the question of how accretion-disk magnetization and the field structure required for jet launching are generated. We continue our work from Mattia & Fendt (Paper I) by considering a nonscalar accretion-disk mean-field α2Ω dynamo in the context of large-scale disk-jet simulations. We now investigate a disk dynamo that follows analytical solutions of the mean-field dynamo theory, essentially based only on a single parameter, the Coriolis number. We thereby confirm the anisotropy of the dynamo tensor acting in accretion disks, allowing both the resistivity and mean-field dynamo to be related to the disk turbulence. Our new model recovers previous simulations by applying a purely radial initial field while allowing for a more stable evolution for seed fields with a vertical component. We also present correlations between the strength of the disk dynamo coefficients and the dynamical parameters of the jet that is launched, and discuss their implications for observed jet quantities. [ABSTRACT FROM AUTHOR]

Topology optimization techniques are very promising methods, because they allow one to obtain an initial conceptual structure starting with minimal information on the design object. This paper proposes a novel topology optimization method that takes into account an asymmetrical rotor structure. The phase angle of stator current is not considered in the topology optimization process, thanks to an asymmetrical rotor. This paper designs the rotor topology of a permanent magnet synchronous generator. The obtained rotors have several topologies by considering permanent magnets with different magnetized directions, and have a better performance than that of Prius generator. [ABSTRACT FROM AUTHOR]

The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the energy of the exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered by means of a properly designed turbogenerator and employed for vehicle propulsion; previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% by employing a 20 kW turbine on a 100 HP rated power thermal unit. The innovative thermal unit here proposed is composed of a supercharged engine endowed with a properly designed turbogenerator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In these two parts, the realistic efficiency of the innovative thermal unit for hybrid vehicle is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors present a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, owing to some assumptions and approximations, allows a fast determination of the proper turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine considered is quite different from the ones commonly employed for turbocharging application; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In the Part 2 paper, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantage that could be achieved by the implementation of the turbogenerator on a hybrid propulsion system is evaluated through the performance prediction model under the different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbocompound system could gain vehicle efficiency improvement between 3.1% and 17.9%, depending on the output power level, while an average efficiency increment of 10.9% was determined for the whole operating range. [ABSTRACT FROM AUTHOR]

This paper addresses the measurement and calculation of unbalanced magnetic pull (UMP) in a wound rotor induction machine. A new rig for measuring UMP is presented. To our knowledge, this type of rig has not been tested before. This paper details the force calculation method and a method for splitting the UMP and torque. Wound rotor induction machines are now popular as generators in wind turbines. It is important to maintain good operation and low bearing wear, and the UMP in these machines is higher than that of the cage-rotor equivalent because the cage damps the UMP. There is little literature on the UMP in a wound rotor machine. [ABSTRACT FROM AUTHOR]