Magnetic Wind Research Articles

Design and Construction of a Mini Magnetic Levitation Train

This article presents the design and construction of a mini magnetic levitation train. The design of the train is based on the theory of 3-phase Linear Induction Motor (LIM). The train consists of two main sections. The first part is the linear induction motor, which is the part that drives the train to move. The second part is the magnetic field winding, which is the part that raises the body of the train to float over the rails. Such train can move forward/backward in the same principle as forward/reverse rotation control of 3-phase induction motors. For that reason, this research controls the forward/backward movement of the train with a magnetic contactor set by using the same circuit as the control of the rotation of the 3-phase induction motor. The designed train can lift 1 mm above the rails and move within a distance of 1.48 m along the length of the rails. The test results showed drive voltage, drive force, average time and drive speed of the train. From the details and results of this article can be used as a guide to create a larger magnetic levitation train, which can be used more effectively.

Effect of Frequency on Arc Motion in Multiple Parallel Contacts’ System

The air circuit breaker (ACB) is required to switch off the short current at various frequencies in the permanent magnet wind power generation system. The movable contact of ACB consists of multiple parallel contacts, and the arc will be ignited when the short-circuit current appears. This paper focuses on the effect of frequency on arc motion in multiple parallel contacts' system. A 3-D magnetohydrodynamic (MHD) model of a multiple parallel contacts' structure is built. In this model, the anode consists of five parallel contacts. The difference in voltage between the near-anode layer and the near-cathode layer is considered. The nonlinear B-H curve of the splitter plate is taken into account. The time-varying electromagnetic field induced by the current loop including electrodes and arc column is calculated. The arc evolution process and effect of frequency on arc motion in multiple parallel contacts' system are analyzed by the arc voltage and the current density distribution. This paper is expected to provide the theoretical references for the optimal design of arc quenching chamber of ACBs.

A Radio Source Coincident with the Superluminous Supernova PTF10hgi: Evidence for a Central Engine and an Analog of the Repeating FRB 121102?

Abstract We present the detection of an unresolved radio source coincident with the position of the Type I superluminous supernova (SLSN) PTF10hgi (z = 0.098) about 7.5 yr post-explosion, with a flux density of F ν (6 GHz) ≈ 47.3 μJy and a luminosity of L ν (6 GHz) ≈ 1.1 × 1028 erg s−1 Hz−1. This represents the first detection of radio emission coincident with an SLSN on any timescale. We investigate various scenarios for the origin of the radio emission: star formation activity, an active galactic nucleus, and a non-relativistic supernova blastwave. While any of these would be quite novel if confirmed, none appear likely when considered within the context of the other properties of the host galaxy, previous radio observations of SLSNe, and the general population of hydrogen-poor supernovae (SNe). Instead, the radio emission is reminiscent of the quiescent radio source associated with the repeating FRB 121102, which has been argued to be powered by a magnetar born in a SLSN or long gamma-ray burst explosion several decades ago. We show that the properties of the radio source are consistent with a magnetar wind nebula or an off-axis jet, indicating the presence of a central engine. Our directed search for fast radio bursts from the location of PTF10hgi using 40 minutes of Very Large Array phased-array data reveals no detections to a limit of 22 mJy (10σ; 10 ms duration). We outline several follow-up observations that can conclusively establish the origin of the radio emission.

Effect of plasma composition on magnetized outflows

In this paper, we study magnetized winds described by variable adiabatic index equation of state in Paczyński & Wiita pseudo-Newtonian potential. We identify the flow solutions with the parameter space of the flow. We also confirm that the physical wind solution is the one which passes through the slow, Alfvén, and fast critical points. We study the dependence of the wind solution on the Bernoulli parameter E and the total angular momentum L. The adiabatic index, which is a function of temperature and composition, was found to be variable in all the outflow solutions. For the same values of the Bernoulli parameter and the total angular momentum, a wind in strong gravity is more accelerated, compared to a wind in Newtonian gravity. We show that flow variables such as the radial and azimuthal velocity components and temperature all depend on the composition of the flow. Unlike the outflow solutions in hydrodynamic regime, the terminal speed of a magnetically driven wind also depends on the composition parameter.

The Origin of the Most Energetic Galactic Cosmic Rays: Supernova Explosions into Massive Star Plasma Winds

We propose that the high energy Cosmic Ray particles up to the upturn commonly called the ankle, from around the spectral turn-down commonly called the knee, mostly come from Blue Supergiant star explosions. At the upturn, i.e., the ankle, Cosmic Rays probably switch to another source class, most likely extragalactic sources. To show this we recently compiled a set of Radio Supernova data where we compute the magnetic field, shock speed and shock radius. This list included both Blue and Red Supergiant star explosions; both data show the same magnetic field strength for these two classes of stars despite very different wind densities and velocities. Using particle acceleration theory at shocks, those numbers can be transformed into characteristic ankle and knee energies. Without adjusting any free parameters both of these observed energies are directly indicated by the supernova data. In the next step in the argument, we use the Supernova Remnant data of the starburst galaxy M82. We apply this analysis to Blue Supergiant star explosions: The shock will race to their outer edge with a magnetic field that is observed to follow over several orders of magnitude B ( r ) × r ∼ c o n s t . , with in fact the same magnetic field strength for such stellar explosions in our Galaxy, and other galaxies including M82. The speed is observed to be ∼0.1 c out to about 10 16 cm radius in the plasma wind. The Supernova shock can run through the entire magnetic plasma wind region at full speed all the way out to the wind-shell, which is of order parsec scale in M82. We compare and identify the Cosmic Ray spectrum in other galaxies, in the starburst galaxy M82 and in our Galaxy with each other; we suggest how Blue Supergiant star explosions can provide the Cosmic Ray particles across the knee and up to the ankle energy range. The data from the ISS-CREAM (Cosmic Ray Energetics and Mass Experiment at the International Space Station) mission will test this cosmic ray concept which is reasonably well grounded in two independent radio supernova data sets. The next step in developing our understanding will be to obtain future more accurate Cosmic Ray data near to the knee, and to use unstable isotopes of Cosmic Ray nuclei at high energy to probe the “piston” driving the explosion. We plan to incorporate these data with the physics of the budding black hole which is probably forming in each of these stars.

Optimization of Ventilation Spacer for Direct-Drive Permanent Magnet Wind Generator

As the rated capacity of the Direct-Drive Permanent Magnet Wind Generator (DDPMWG) increases, the heat produced from the generator’s inner components also increases and it becomes difficult to transfer the inner heat to the ambient. The ventilation spacer has a significant influence on the heat transfer process of DDPMWG. Thus, this paper focuses on the optimization of the ventilation spacer on the thermal field of DDPMWG. Firstly, the fluid flow and heat transfer coupled numerical calculation model is established. The physical model, composed of two half-slots and one tooth of DDPMWG, is established due to the structural symmetries to save the calculations. The sources and boundary conditions for the thermal calculations are also given. Five new ventilation spacers, compared with the original one, are proposed to investigate the thermal fields. The pressure drop and temperature field are compared to find the optimized ventilation spacer for the DDPMWG. The criteria are also presented for judging the heat transfer capacity. To validate the optimized ventilation spacer, the temperature rises of the armature winding with original and optimized ventilation spacers are measured. It proves that the armature winding’s temperature rise of the optimized ventilation spacer is about 4.7 K lower than that with the original ventilation spacer.

Effect of Different Angular Momentum Transport Mechanisms on the Distribution of Water in Protoplanetary Disks

Abstract The snow line in a protoplanetary disk demarcates regions with H2O ice from regions with H2O vapor. Where a planet forms relative to this location determines how much water and other volatiles it forms with. Giant-planet formation may be triggered at the water–snow line if vapor diffuses outward and is cold-trapped beyond the snow line faster than icy particles can drift inward. In this study, we investigate the distribution of water across the snow line, considering three different radial profiles of the turbulence parameter α(r), corresponding to three different angular momentum transport mechanisms. We consider the radial transport of water vapor and icy particles by diffusion, advection, and drift. We show that even for similar values of α, the gradient of α(r) across the snow line significantly changes the snow line location, the sharpness of the volatile gradient across the snow line, and the final water/rock ratio in planetary bodies. A profile of radially decreasing α, consistent with transport by hydrodynamic instabilities plus magnetic disk winds, appears consistent with the distribution of water in the solar nebula, with monotonically increasing radial water content and a diverse population of asteroids with different water content. We argue that Σ(r) and water abundance are likely a diagnostic of α(r) and thus of the mechanism for angular momentum transport in inner disks.

Magnetic braking and damping of differential rotation in massive stars

Fragmentation of highly differentially rotating massive stars that undergo collapse has been suggested as a possible channel for binary black hole formation. Such a scenario could explain the formation of the new population of massive black holes detected by the LIGO/VIRGO gravitational wave laser interferometers. We probe that scenario by performing general relativistic magnetohydrodynamic simulations of differentially rotating massive stars supported by thermal radiation pressure plus a gas pressure perturbation. The stars are initially threaded by a dynamically weak, poloidal magnetic field confined to the stellar interior. We find that magnetic braking and turbulent viscous damping via magnetic winding and the magnetorotational instability in the bulk of the star redistribute angular momentum, damp differential rotation and induce the formation of a massive and nearly uniformly rotating inner core surrounded by a Keplerian envelope. The core + disk configuration evolves on a secular timescale and remains in quasi-stationary equilibrium until the termination of our simulations. Our results suggest that the high degree of differential rotation required for $m=2$ seed density perturbations to trigger gas fragmentation and binary black hole formation is likely to be suppressed during the normal lifetime of the star prior to evolving to the point of dynamical instability to collapse. Other cataclysmic events, such as stellar mergers leading to collapse, may therefore be necessary to reestablish sufficient differential rotation and density perturbations to drive nonaxisymmetric modes leading to binary black hole formation.

Health condition assessment of wind turbine generators based on supervisory control and data acquisition data

As the running time of a wind turbine generator unit (WTGU) increases, the ageing and wear of its components will be aggravated gradually, which leads to deterioration of its operation condition. In order to ensure the safe and stable operation of WTGU and prolong its service life, it is of great significance to know the health condition of the WTGU and reasonably arrange maintenance. Based on the structure of the WTGU and the operation principle of the wind turbine generator (WTG), the condition assessment indexes of WTG were built, and the factors influencing the assessment index were determined. The relationship function between the assessment indexes and their influencing factors was established by using the least square support vector machine, which was used to determine the dynamic limitation of condition assessment index of WTG. The dynamic weight of each assessment index was used to characterise the influence of deterioration degree of different components on WTG conditions. Then the health conditions of WTG were evaluated using a similar cloud and fuzzy comprehensive assessment method separately. Finally, the proposed methods were verified by two examples including a direct-drive permanent magnet wind generator and a doubly-fed wind generator.

The synchrotron maser emission from relativistic shocks in Fast Radio Bursts: 1D PIC simulations of cold pair plasmas

ABSTRACT The emission process of Fast Radio Bursts (FRBs) remains unknown. We investigate whether the synchrotron maser emission from relativistic shocks in a magnetar wind can explain the observed FRB properties. We perform particle-in-cell (PIC) simulations of perpendicular shocks in cold pair plasmas, checking our results for consistency among three PIC codes. We confirm that a linearly polarized X-mode wave is self-consistently generated by the shock and propagates back upstream as a precursor wave. We find that at magnetizations σ ≳ 1 (i.e. ratio of Poynting flux to particle energy flux of the pre-shock flow) the shock converts a fraction $f_\xi ^{\prime } \approx 7 \times 10^{-4}/\sigma ^2$ of the total incoming energy into the precursor wave, as measured in the shock frame. The wave spectrum is narrow-band (fractional width ≲1−3), with apparent but not dominant line-like features as many resonances concurrently contribute. The peak frequency in the pre-shock (observer) frame is $\omega ^{\prime \prime }_{\rm peak} \approx 3 \gamma _{\rm s | u} \omega _{\rm p}$, where γs|u is the shock Lorentz factor in the upstream frame and ωp the plasma frequency. At σ ≳ 1, where our estimated $\omega ^{\prime \prime }_{\rm peak}$ differs from previous works, the shock structure presents two solitons separated by a cavity, and the peak frequency corresponds to an eigenmode of the cavity. Our results provide physically grounded inputs for FRB emission models within the magnetar scenario.

A simple screening current-induced magnetic field estimation method for REBCO pancake coils

The development of NMR/MRI REBa2Cu3Oy (REBCO, RE = rare earth) magnets is happening all over the world. It has been found that screening current-induced magnetic fields (SCMFs) are a serious problem for NMR/MRI magnets wound with REBCO tapes. The reduction of SCMFs is strongly desired, and the estimation of SCMFs is also desired at the design stage of REBCO magnets. In order to evaluate a SCMF, a finite element method (FEM) or a boundary integration method is needed thus far, and a high-level simulation technique is required. In this paper, we develop an easy method to estimate a SCMF without a high-level simulation technique. In this method, the inductance of a winding turn is calculated and then a screening current is estimated according to the magnetic field penetrating into the winding turn. The SCMF is obtained from the estimated screening current. The SCMFs computed by the proposed method were compared with measurements and simulation results of the FEM. The results agreed well, but we can see a large difference. However, the SCMFs found by the proposed method are accurate enough to know they are at the design stage without the use of a high-level simulation technique.

High-Frequency <italic>LLC</italic> Resonant Converter With Magnetic Shunt Integrated Planar Transformer

Achieving high efficiency and high power density is emerging as a goal in many power electronics applications. LLC resonant converter has been proved as an excellent candidate to achieve this goal. To achieve smaller size of passive components, the resonant inductor in the LLC converter is usually integrated into the transformer by utilizing its leakage inductance. However, the leakage inductance of the transformer is usually insufficient and thus the LLC converter has to be operated in a limited frequency range (this limits the input voltage range accordingly), otherwise the power efficiency will drop dramatically. Therefore, a larger resonant inductance in the LLC converter is expected to operate in a wider input voltage range. This paper proposes a new method to create a larger resonant inductance by using a magnetic shunt integrated into planar windings. The accurate leakage inductance modeling, calculation, and optimal design guideline for LLC planar transformer, including optimal magnetic shunt selection and winding layout, are presented. A 280–380 V input and output 48 V–100 W half-bridge LLC resonant converter with 1 MHz resonant frequency is built to verify the design methodology. A comparison is made between two converters with the same parameters, one using magnetic shunt integrated transformer and the others using traditional planar transformer and external inductor. Experimental result shows the proposed converter with magnetic shunt is capable to achieve comparable high efficiency and regulation capability with the other under a wide input voltage, which verifies the optimal design methodology. Above all, this magnetics integration methodology reduces the whole converter's volume and thus increases the power density.

Modeling and Operation of a Bearingless Fixed-Pole Rotor Induction Motor

The rotor currents are induced by both suspension force winding magnetic field and torque winding magnetic field in the traditional bearingless induction motors (BIMs). Due to the currents induced by the suspension force winding, there are errors in the generation of radial suspension forces. To address such problems, a novel BIM with fixed-pole rotor, called bearingless fixed-pole rotor induction (BFPRI) motor is proposed. The structure of BFPRI motor is first analyzed and the mathematical models of radial suspension forces are deduced. Based on the finite element analysis, the induced currents and radial suspension forces are also investigated and compared with the traditional BIM. Finally, the prototype motor is built and experimental research is carried out. In this novel motor, only the torque winding magnetic field induces currents in the rotor, which makes the precision of radial suspension forces higher and thereby reduces the complexity of BIM control system. The effectiveness of the proposed BFPRI motor is validated by both simulation and experiments.

Physics of “Cold” Disk Accretion onto Black Holes Driven by Magnetized Winds

Disk accretion onto black holes is accompanied by collimated outflows (jets). In active galactic nuclei (AGN), the kinetic energy flux of the jet (jet power or kinetic luminosity) may exceed the bolometric luminosity of the disk by a few orders of magnitude. This may be explained in the framework of the so called “cold” disk accretion. In this regime of accretion, the disk is radiatively inefficient because practically all the energy released at the accretion is carried out by the magnetized wind. This wind also provides efficient loss of the angular momentum by the matter in the disk. In this review, the physics of the accretion driven by the wind is considered from first principles. It is shown that the magnetized wind can efficiently carry out angular momentum and energy of the matter of the disk. The conditions when this process dominates conventional loss of the angular momentum due to turbulent viscosity are discussed. The “cold” accretion occurs when the viscous stresses in the disk can be neglected in comparison with impact of the wind on the accretion. Two problems crucial for survival of the model of “cold” accretion are considered. The first one is existence of the magnetohydrodynamical solutions for disk accretion purely due to the angular momentum loss by the wind. Another problem is the ability of the model to reproduce observations which demonstrate existence of the sources with kinetic power of jets 2–3 orders of magnitude exceeding the bolometric luminosity of disks. The solutions of the problem in similar prescriptions and numerical solutions without such an assumption are discussed. Calculations of the “unavoidable” radiation from the “cold” disk and the ratio of the jet power of the SMBH to the bolometric luminosity of the accretion disk around a super massive black hole are given in the framework of the Shakura and Sunyaev paradigm of an optically thick α -disk. The exploration of the Fundamental Plane of Black Holes allows us to obtain semi empirical equations that determine the bolometric luminosity and the ratio of the luminosities as functions of the black hole mass and accretion rate.

Instantaneous Thrust Control of the Linear Switched Reluctance Motors with Segmental Translator

The linear switched reluctance machine (LSRM) has all advantages of rotary switched reluctance machine including simple and rugged structure, absence of magnetic material and windings on translator, high reliability and appropriate performance over a wide range of speed. Like rotary switched reluctance motor with segmental rotor, segmental translator linear switched reluctance motor (STLSRM) has capability to produce higher output power/weight in comparison to the conventional linear switched reluctance motors. Due to high advantages of the STLSRM drive, various control algorithms including current control, model predictive control, direct force control, universal control and force distribution function are investigated for the first time to control the instantaneous thrust of this motor. Applying these algorithms to a typical three-phase STLSRM, simulation results are presented and they are compared together from the force ripple reduction point of view.

Energy efficient heat supply system for electric power facilities

The aim of the work is to confirm the possibility of creating an energy-saving heat supply system for power facilities by using computer modelling, analysis of the potential use of heat losses of electromagnetic energy in magnetic circuits and windings of transformers of substations, as well as the development of schemes for heat recovery losses for heat supply of power facilities. Computer simulation of electromagnetic and thermophysical processes in the power oil-filled transformer is carried out. Energy losses in windings, hysteresis and eddy currents in the magnetic circuit, as well as temperature and heat flux fields in the longitudinal and transverse sections of the oil-filled power transformer in idle and short-circuit modes were determined. The transformer performance in terms of heat recovery losses was evaluated. The possible volumes of heat extraction for heat supply depending on the power of the transformer are determined. The automated oil-water system of heat recovery of the transformer for heating of electric power facilities is proposed. The significance of the obtained results for the construction industry is to confirm the possibility of creating an energy-saving heat supply system for electric power facilities while maintaining the operational characteristics of the transformer based on computer modelling; the significant potential of using the heat loss of power transformers of substations is shown, an automated heat supply system for electric power facilities is proposed.

Pulse Magnetization of Strap Toroidal Magnetic Core

Diffusion of the pulse magnetic field into the metal of the toroidal magnetic core wound by a transformer steel strap is considered. The 1-D numerical model has been developed, which takes into account the viscous-type dynamic losses of magnetization, as well as the eddy currents. The parameter of viscous-type dynamic losses of magnetization was measured on samples of cold-rolled anisotropic transformer steel. The processes of magnetic field propagation in the strap, when the transformer is switched to the voltage source, have been analyzed, and the iteration algorithm of calculation of magnetic field in the strap has been developed. The experimental data have confirmed the obtained calculation results. The problems of application of transformer steel in pulse transformers are considered.

Analysis and Performance Evaluation of an Efficient Power-Fed Permanent Magnet Adjustable Speed Drive

This paper proposes a novel power-fed permanent magnet adjustable speed drive (PF-PMASD) to regulate the speeds of pumps and fans for energy saving. The drive features that the slip power induced in the wound rotor of the drive can be fed to the power grid by a power electronic converter. The structure, operation principle, and control strategy of the drive are introduced and investigated. The mathematical model of the PF-PMASD is built by referring to the models of the traditional permanent magnet synchronous machine and wound rotor induction motor, based on which the power-size equation for the drive is deduced. The losses and efficiencies of the drive under different slips are also calculated and evaluated. The relationships between the slip and the duty cycle of the insulated-gate bipolar transistor in the boost chopper are revealed by the mathematical model of the control unit. The steady characteristics including electromotive forces, phase currents, and torques under different operation states are computed and analyzed comprehensively by finite-element analysis. The speed regulation characteristics, the power factor, and the energy-saving capabilities of the drive are investigated by experimental test. The analysis results indicate that the proposed PF-PMASD possesses a remarkable speed regulation capability with high efficiency.

Temperature Rise Effect of Permanent Magnet Wind Turbine in Different Field Settings

Temperature rise is an essential factor affecting the safety operation of electric machines. An appropriate solving domain is the first step to consider when calculating the temperature rise. However, the effect of solving domain setting on the calculation results of electric machine temperature rise has not been deeply discussed. In this paper, a 3MW permanent magnet wind generator is taken as an example. Based on the electrical and numerical heat transfer theories, two different solving domain models are established to compare the flow thermal characteristics of the internal and external ventilated paths. The fluid velocity changes in external ventilated path, the central section temperature rise and the velocity trace distribution of the internal ventilated path are compared in detail. Furthermore, the temperature rise of each component is analyzed. It is found that the fluid development in the generator is affected by solving domain selection. The results can provide a reference for accurate calculation of temperature rise of permanent magnet wind generator.

A Study and Design Construction of Vertical Axis Wind Turbine (VAWT) to Operate on Wind Energy

It involves about a study on wind turbine especially vertical wind turbine. The design development of vertical non contact magnetic wind turbine is under study and consideration. With the aid of plywood material a vertical wind turbine has been prepared. Instead of bearing, the contactless magnets are utilized for holding and rotation of the turbine. Such turbine under study, design, development has been taken under consideration for domestic use as well as at the divider of the link road or on the overhead bridge or in the bus or railway stations. The horizontal wind turbines are heavy and bulky in construction. So it has been worked considering the latest trend of technology about vertical wind turbine.