Electrodynamic Forces Research Articles

MATHEMATICAL MODEL TO CALCULATE THE TRAJECTORIES OF ELECTROMAGNETIC MILL OPERATING ELEMENTS

The purpose of the research under consideration is to develop a mathematical model to calculate the trajectories of the ferromagnetic operating elements (millstones) of an electromagnetic mill, moving in a rotating magnetic field under electrodynamic and hydrodynamic resistance forces being limited by the space of the mill’s working chamber. The millstone motion is described through the equations of plane motion of arbitrary-shaped two-dimensional body. The driving forces of this motion are determined on the basis of the approximation of the tabulated functions connecting the module and the orientation of the equivalent force applied to the millstone, with its position in the working chamber and composite MMF phase of mill inductor winding. These tabulated functions are derived from the estimation of the magnetic field inside a working chamber with millstones, in two-dimensional quasi-stationary approximation, using FEM analysis. The publication contains the approximation algorithm for these tabulated vector functions of a vector argument, mathematical statement of millstones trajectories calculating, and analysis of mathematical experiments results that make it possible to evaluate the adequacy of the model. The developed tool enables conducting quantitative analysis of grinding/mixing process and will help to establish relationships between the electromagnetic mill design parameters and its performance. References 21, figures 6.

Solar activity dependence of medium-scale traveling ionospheric disturbances using GPS receivers in Japan

In order to reveal solar activity dependence of the medium-scale traveling ionospheric disturbances (MSTIDs) at midlatitudes, total electron content (TEC) data obtained from a Global Positioning System (GPS) receiver network in Japan during 22 years from 1998 to 2019 were analyzed. We have calculated the detrended TEC by subtracting the 1-h running average from the original TEC data for each satellite and receiver pair, and made two-dimensional TEC maps of the detrended TEC with a spatial resolution of 0.15° × 0.15° in longitude and latitude. We have investigated MSTID activity, defined as delta I/overline{I}, where delta I and overline{I} are standard deviation of the detrended TEC and the average vertical TEC within the area of 133.0°–137.0° E and 33.0°–37.0° N for 1 h, respectively. From each 2-h time series of the detrended TEC data within the same area as the MSTID activity, auto-correlation functions (ACFs) of the detrended TEC were calculated to estimate the horizontal propagation velocity and direction of the MSTIDs. Statistical results of the MSTID activity and propagation direction of MSTIDs were consistent with previous studies and support the idea that daytime MSTIDs could be caused by atmospheric gravity waves, and that nighttime MSTIDs were caused by electro-dynamical forces, such as the Perkins instability. From the current long-term observations, we have found that the nighttime MSTID activity and occurrence rate increased with decreasing solar activity. For the daytime MSTID, the occurrence rate increased with decreasing solar activity, whereas the MSTID activity did not show distinct solar activity dependence. These results suggest that the secondary gravity waves generated by dissipation of the primary gravity waves propagating from below increase under low solar activity conditions. The mean horizontal phase velocity of the MSTIDs during nighttime did not show a distinct solar activity dependence, whereas that during daytime showed an anticorrelation with solar activity. The horizontal phase velocity of the daytime MSTIDs was widely distributed from 40 to 180 m/s under high solar activity conditions, whereas it ranged between 80 and 200 m/s, with a maximum occurrence at 130 m/s under low solar activity conditions, suggesting that gravity waves with low phase velocity could be dissipated by high viscosity in the thermosphere under low solar activity conditions.

Dynamic Analysis and Libration Control of Electrodynamic Tether for Reboost Applications

Electrodynamic tethers can be employed as an immensely promising propulsion system for boosting the altitude of spacecraft, cite instance space stations, satellites, and the like, which ameliorates the expenditure of fuel and minimizes detrimental spacecraft impacts. This paper analyzes the libration dynamics and stability of reboost spacecraft with insulation electrodynamic tethers. A key aspect of spacecraft reboost with an electrodynamic tether is how to keep the tether aligned with the local vertical and stabilized in the context of external disturbances. It has been shown in the current research that the librational instability results in the tether slackness and swings in long-term motion without effective control. Moreover, electrodynamic force (Ampere force) is regarded as a distributed load acting on the tether causing tether deformations which may be detrimental if severe. Aiming at the problem, an optimal control method and PID are given to stabilize the libration motion by modulating the tether current. The dynamical model of the electrodynamic tether system is established using Lagrange equations of the second kind under considering tether deformation and control laws are proposed based on the model. The effectiveness of libration stability control is validated through numerical results in which a current regulation law with appropriate control parameters is used for the libration motion of electrodynamic tether system.

Магнитное поле и силы в гибридной системе левитации высокоскоростного транспорта

A hybrid system designed to provide levitation for a high-speed on-ground vehicle at low traveling speeds is considered. The levitation is obtained due to the simultaneous use of electrodynamic repulsion forces and electromagnetic attraction forces. Structurally, this is implemented by using two longitudinal tracks. One of them, which is electrically conducting and nonmagnetic, is located under the vehicle excitation solenoid, and the second one, which is ferromagnetic, is arranged above the vehicle excitation solenoid only on the acceleration, braking and station sections. To ensure the equality of the resulting levitation force to the vehicle weight on all of these motion sections, the ferromagnetic track is made so that its area that participates in producing the attraction force varies depending on the vehicle motion speed. To avoid the negative effect of eddy currents induced in the ferromagnetic track, the latter is made of plates electrically insulated from each other. In performing the design calculations, the tracks were represented as plates of infinite size. An analytical solution for the magnetic field and levitation forces is obtained. It is shown that in particular cases, the results obtained from these solutions coincide with the results obtained previously by other authors for the conventional repulsion levitation system. The possibility of levitation at low speeds and stops is confirmed, and it is pointed out that a somewhat growth in the braking force does not has an essential influence on the traction linear motor power output

Gravitational Dispersion Forces and Gravity Quantization

The parallel development of the theories of electrodynamical and gravitational dispersion forces reveals important differences. The former arose earlier than the formulation of quantum electrodynamics so that expressions for the unretarded, van der Waals forces were obtained by treating the field as classical. Even after the derivation of quantum electrodynamics, semiclassical considerations continued to play a critical role in the interpretation of the full results, including in the retarded regime. On the other hand, recent predictions about the existence of gravitational dispersion forces were obtained without any consideration that the gravitational field might be fundamentally classical. This is an interesting contrast, as several semiclassical theories of electrodynamical dispersion forces exist although the electromagnetic field is well known to be quantized, whereas no semiclassical theory of gravitational dispersion forces was ever developed although a full quantum theory of gravity is lacking. In the first part of this paper, we explore this evolutionary process from a historical point of view, stressing that the existence of a Casimir effect is insufficient to demonstrate that a field is quantized. In the second part of the paper, we show that the recently published results about gravitational dispersion forces can be obtained without quantizing the gravitational field. This is done first in the unretarded regime by means of Margenau’s treatment of multipole dispersion forces, also obtaining mixed potentials. These results are extended to the retarded regime by generalizing to the gravitational field the approach originally proposed by McLachlan. The paper closes with a discussion of experimental challenges and philosophical implications connected to gravitational dispersion forces.

Electrodynamic Force, Casimir Effect, and Stiction Mitigation in Silicon Carbide Nanoelectromechanical Switches.

Logic switches enabled by nanoelectromechanical systems (NEMS) offer abrupt on/off-state transition with zero off-state leakage and minimal subthreshold swing, making them uniquely suited for enhancing mainstream electronics in a range of applications, such as power gating, high-temperature and high-voltage logic, and ultralow-power circuits requiring zero standby leakage. As NEMS switches are scaled with genuinely nanoscale gaps and contacts, quantum mechanical electrodynamic force (EDF) takes an important role and may be the ultimate cause of the plaguing problem of stiction. Here, combined with experiments on three-terminal silicon carbide (SiC) NEMS switches, a theoretical investigation is performed to elucidate the origin of EDF and Casimir effect leading to stiction, and to develop a stiction-mitigation design. The EDF calculation with full Lifshitz formula using the actual material and device parameters is provided. Finite element modeling and analytical calculations demonstrate that EDF becomes dominant over elastic restoring force in such SiC NEMS when the switching gap shrinks to a few nanometers, leading to irreversible stiction at contact. Artificially corrugated contact surfaces are designed to reduce the contact area and the EDF, thus evading stiction. This rational surface engineering reduces the EDF down to 4% compared with the case of unengineered, flat contact surfaces.

(Keynote) Biosensor and Bioreactor Performance of a Chemically Modified Electrodynamic Microfluidic Channel

Numerous biological sensing devices have been developed for medical and health care purposes, to date. However, many cases demand a simple, inexpensive, and efficient device, concurrently performing the reaction, separation, and detection. Hence, we have established the separation detection method of molecules and nanoparticles using a symmetrical AC electric field applied electrochemical microfluidic device fabricated with a screen printing technique (EMC). The separation principle was also evaluated with the lateral movement of targets perpendicularly against the channel walls under the AC field, which was analyzed by simulation using the mathematically derived equation from Newtonian fluid mechanics.[1] The device can be used for various reactions and detections of complex biological species in the channel. Here, some applications will be introduced; 1) separation detection of cancer cells, 2) simultaneous analysis of glycated hemoglobin family, and 3) aptamer generation, separation, and biosensor fabrication.The circulating tumor cells (CTCs) are dare rare, and account for as low as one cell per 109 hematologic cells in the blood of metastatic cancer patients, and they are very similar in size as compared to some of the WBCs, hence, their separation is a tremendous challenge. To date, CellSearch® is the only FDA approved method for sorting CTCs from blood samples, where only cells of epithelial origin can be separated. Thus, a new robust method is demanded to separate and analyze the CTCs for the early-stage diagnosis of cancers. Here, the primary criterion for their separation is electrodynamic force to differentiate cells in size (or mass) and surface charge. To additionally enhance the performance, the channel wall inside was modified with a positively charged lipid to interact the cell surface. The separated cells in the channel were detected amperometrically at the channel end. Here, the electrochemically inactive cancer cells have been selectively detected in blood using electrochemically active drugs. The device was able to separate a single cell with 92.0 ± 0.5 % efficiency. 37 patient blood samples from different origins were separated and detected with the detection rate of 91%.[2]Glycated hemoglobin (HbA1c) is clinically important, since its concentration is directly or indirectly linked with various diseases including diabetes, nephropathy, retinopathy, atherosclerosis, and other perivascular diseases. Hence, the simultaneous detection of hemoglobin (Hb) and glycated hemoglobin fractions (HbA1c, HbAld1+2, HbAle, HbAld3a, HbAla+b, HbA2, and HbAld3b) is crucial. They were separated and detected using the EMC with a catalytic redox mediators-modified sensor. The different types of redox mediators were evaluated to achieve the efficient detection. Under optimized conditions, linear dynamic ranges for Hb and HbA1c among their fractions were obtained between 1.0×10−9 to 3.5 x 10-6 M and 3.0×10−9 to 0.6 x 10-6 M with the detection limit of 8.1×10−10 ± 3.0×10−11and 9.2×10−10 ± 5×10−11 M, respectively.In addition, we have demonstrated the device for the aptamer generation and isolation, where the generated them were applied for a model protein, PvLDH for malaria diagnosis. Here, the target protein bound on the EMC channel walls induced the specific binding of DNA library molecules. In case of 60 min inducing, the partitioning efficiency between target protein and the library was attained to be 1.67 x 107 with the background of 5.56 × 10-6, which was confirmed by the qPCR. The in situ method has successfully generated and separated five aptamers in different sequences by one round generation. The dissociation constants (Kd) of selected aptamers were determined employing both electrochemical impedance spectroscopy (EIS) and fluorescence method. The sensing performances of five aptamers were evaluated for the PvLDH detection after individual immobilization on the screen-printed array electrodes. The most sensitive one revealed the detection limit of 7.8 ± 0.4 fM. The reliability of the sensor was demonstrated by comparing with the other malaria sensors.Conclusively, the screen-printed electrochemical microfluidic channel with low potential AC electric field has been successfully demonstrated for the simultaneous detection of complex biological samples. It is respected to be applied in various research fields, such as bioreactor and biosensor, chemical reactor and sensor, medical device, separation science, etc.References M. M. Hossain, N G Gurudatt, K.D Seo, D.S. Park, H. Hong, E.S. Yeom, J. H. Shim, and Y.B. Shim, Anal. Chem. 91 (2019) 14109−14116.N.G. Gurudatt, S.Chung, J.M. Kim, M.H. Kim, D.K.Jung, J.Y. Han, Y.B. Shim, Biosensors and Bioelectronics 146 (2019) 111746.M.M. Hossain, J.M. Moon, N.G. Gurudatt, D.S. Park, C. S. Choi, Y.B. Shim, Biosensors and Bioelectronics 142 (2019) 111515.

Quaternionic electrodynamics

We develop a quaternionic electrodynamics and show that it naturally supports the existence of magnetic monopoles. We obtained the field equations, the continuity equation, the electrodynamic force law, the Poynting vector, the energy conservation, and the stress-energy tensor. The formalism also enabled us to generalize the Dirac monopole and the charge quantization rule.

Calculations of Electrodynamic Forces in Three-Phase Asymmetric Busbar System with the Use of FEM

Proper busbar selection based on analytical calculations is of great importance in terms of power grid functioning and its safe usage. Experimental tests concerning busbars are very expensive and difficult to be executed. Therefore, the great advantage for setting the valid parameters for busbar systems components are analytical calculations supported by FEM (finite element method) modelling and analysis. Determining electrodynamic forces in busbar systems tends to be crucial with regard to subsidiary, dependent parameters. In this paper analytical calculations of asymmetric three-phase busbar system were carried out. Key parameters, like maximal electrodynamic forces value, mechanical strength value, busbar natural frequency, etc., were calculated. Calculations were conducted with an ANSYS model of a parallel asymmetric busbar system, which confirmed the obtained results. Moreover, showing that a model based on finite elements tends to be very helpful in the selection of unusually-shaped busbars in various electrotechnical applications, like switchgear.

Reduction of auto seismic oscillations of the ballistic laser gravimeter on account of the excitation of the induction-dynamic catapult by a pulse packet

In order to reduce auto seismic oscillations in the ballistic laser gravimeters (BLG) with a symmetric method of measuring the gravitational acceleration (GA), an induction-dynamic catapult (IDC) is used, which is excited by a pulse packet from a capacitive energy storage unit (CES). With such excitation, a decrease in the amplitude of auto seismic oscillations is achieved by reducing the amplitude and increasing the duration of action of the electrodynamic force that occurs in the IDC when pushing the test body (TB).A mathematical model of the IDC of the ballistic laser gravimeter with a symmetric method of measuring the GA is developed and the modeling of its electromechanical characteristics is carried out. Various methods of generating a packet of excitation pulses of the IDC inductor are considered and the characteristics of electrodynamic force pulses that accelerate the armature of the catapult with TB are investigated for them. The effect of IDC excitation by a pulse packet on the auto seismic component of the GA measurement is investigated. It is shown that on account of the excitation of the IDC by a ten-pulse packet, the auto seismic component of the uncertainty of the GA measurement by ballistic gravimeters can be reduced several (3–5) times in comparison with the excitation of the catapult by a single pulse.

Effect of Pulse Current on Residual Stresses in AMg6 Aluminum Alloy in Electrodynamic Treatment

The development of energy-efficient methods of controlling the stress state of metallic materials and welded joints is topical for modern production. One of such methods is electrodynamic treatment (EDT). It is based on the passage of electric current pulses (ECP) through the metal, time-synchronized with an impact load initiated by electrodynamic forces. In this case, an electrodynamic deformation process and a process of formation of elastic strain waves occur simultaneously in the material being treated; they are defined as “electrodynamic impact”, the result of which is a local stress relaxation in the metal. The developed mathematical model of the formation of stress and strain fields during EDT, which is based on the motion of an elastoplastic medium, does not take into account the effect of ECPs on dynamic relaxation processes. A computational and experimental assessment of the effect of ECPs, which is based on the experimental assessment of the stress state and microindentation of AMg6 aluminum alloy plates after EDT without and with the passage of ECPs through the metal being treated, has been performed by the mathematical modeling of the EDT process taking into account microindentation results. The passage of ECPs contributes to an increase in tensile plastic strains and hence to an increase in residual compressive stresses (provided that the specimens to be treated are rigidly fixed). The reliability of the procedure has been confirmed by the results of evaluating the distribution of residual welding stresses in AMg6 alloy butt joints after EDT.

EXCITATION WITH A SERIES OF PULSES OF A LINEAR PULSE ELECTRODYNAMIC TYPE CONVERTER OPERATING IN POWER AND HIGH-SPEED MODES

Purpose. The aim of the article is to increase the efficiency of linear pulse electrodynamic type converter (LPEC) when operating in high-speed and force modes by reducing the amplitude of the recoil force by exciting its windings with a series of pulses from the capacitive energy storage (CES). Methodology. Using the LPEC mathematical model, in which the equations describing the interconnected electrical, magnetic, mechanical and thermal processes are presented in a recursive form, the electrodynamic and electromechanical characteristics of LPEC are simulated by excitation by a single and a series of pulses from CES sections. Results. It was found that when a single pulse is excited by an LPEC operating in a high-speed mode, in which the armature accelerates the actuator, compared with the force mode in which the armature is inhibited, the current amplitude in the windings decreases by 7.5 %, and the amplitudes of electrodynamic force (EDF) – by 21.8 %, impulse values of EDF – by 27.1 %. In this case, the armature winding with the actuating element accelerates to a speed of 7.1 m/s. When excited by a series of pulses from the same sections of the CES during LPEC operation in the force mode, the amplitudes of the current pulses and the EDF are practically unchanged, and when operating in high-speed mode, the amplitudes of the currents and the EDF gradually decrease. Both in power and in high-speed operating modes, an increase in the number of excitation pulses while conserving the energy of the CES leads to a decrease in the main indicators of LPEC. But by reducing the amplitude of the EDF, which manifests itself as a recoil force, the efficiency of LPEC increases. Originality. It is shown that the excitation of LPEC by a series of pulses increases the efficiency of LPEC when operating in high-speed and power modes, providing a minimum amplitude of the EDF, which determines the recoil force acting on the inductor winding. Practical value. For LPEC operating in high-speed mode, it is proposed to reduce the maximum current amplitudes and EDF due to the sequential increase in capacitances of sections of the CES, forming a series of excitation pulses. For LPEC, operating in force mode, it is advisable to use the same capacities of all sections of the CES.

Improved detachable electrodynamic cleaning system for dust removal from soiled photovoltaic panels

A detachable cleaning device that utilizes electrodynamic force has been improved to clean hardly adhered dust particles owing to the moisture absorption from the surface of photovoltaic (PV) panels. The device comprises parallel screen electrodes attached in a plastic frame. When a high ac voltage is applied to the parallel screen electrodes (whose lower part is set on a soiled PV panel), the generated electrodynamic force acts on the particles under the lower electrode. A flip-flop motion of the particles arises between the electrodes owing to the electrodynamic force as well as some particles that pass through the openings of the upper screen electrode and fall downward along the inclined panel owing to gravitational force. Hence, the dust deposited on the panel is cleaned. Previously, it has been demonstrated that dust is removed efficiently from the surface of an inclined panel by applying a low-frequency high-voltage. However, the performance is low for particles that are strongly fixed on the panel. Three countermeasures are proposed herein to improve the cleaning of dust particles: by adjusting the operational scheme, improving the electrode configuration, and utilizing airflow. This improved technology is expected to realize the efficient operation of large-scale PV power generation plants constructed in deserts.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ КОНТРОЛЯ СОСТОЯНИЯ ОБМОТОК ВЫСОКОВОЛЬТНЫХ ТРАНСФОРМАТОРОВ НА ОСНОВЕ КОММУТАЦИОННЫХ ИМПУЛЬСОВ

Актуальность исследования. На всех этапах технологической цепи добычи, транспортировки и последующего использования геологических ресурсов применяется широкий спектр высоковольтного оборудования, существенную часть которого составляют высоковольтные трансформаторы различных типов, назначений и классов напряжения. Поэтому общая энергетическая эффективность и надежность производства геологических ресурсов существенно зависит от состояния высоковольтного трансформаторного оборудования. Дефектное состояние одной трансформаторной единицы часто является причиной внезапной аварийной остановки всей технологической цепи комплексного производственного процесса. Результатом подобного инцидента является пожар, сопровождаемый взрывом высоковольтного ввода, разлив масла, загрязнение окружающей среды и материальный ущерб, исчисляемый многомиллионными суммами. К возникновению дефектного и, как следствие, аварийного состояния приводит ряд электрофизических и эксплуатационных факторов, воздействующих на изоляцию и активную часть трансформаторов. В свою очередь наиболее проблемным элементом активной части трансформатора оказываются обмотки как высокого, так и низкого напряжения, в которых появляются механические смещения как результат воздействия пондеромоторных сил токов короткого замыкания. Подобные дефекты могут развиваться длительное время, и трансформатор может находиться в работе в номинальном режиме. На некотором этапе развития дефект становится критическим, повреждения изоляции обмотки при очередном коротком замыкании ведут к возгоранию с последующей аварией. Для предупреждения подобных ситуаций необходима эффективная технология контроля состояния обмоток. Стандартные методы являются малоэффективными для выявления дефектов обмотки на ранних стадиях развития. Среди новых и рекомендованных международными экспертными институтами МЭК и СИГРЭ являются модификации импульсного метода, прежде всего метод частотного анализа. Однако, не смотря на признание как наиболее достоверного и перспективного, указанный метод далеко не всегда позволяет обнаружить дефекты обмоток, особенно на ранних этапах развития. Кроме того, обязательным условием применения технологии метода частотного анализа является полное снятие напряжения, расшиновка трансформатора и использование специальной аппаратуры контроля. При этом для получения достоверных результатов диагностики необходимо наличие специальных эталонных сигналов – нормограмм, которые отсутствуют практически для всего парка трансформаторов, используемых в технологических процессах добычи и переработки геологических ресурсов. Эти факторы снижают общую эффективность технологии метода частотного анализа. Поэтому в настоящее время вопрос по исследованию и разработке технологии контроля состояния обмоток под рабочим напряжением является в полной мере актуальным. Цель: экспериментальное исследование принципиальной возможности контроля состояния обмоток трансформатора на основе процессов коммутации в высоковольтной сети. Методы: метод моделирования на реальном физическом объекте. В трансформаторе НТМИ-6 на одной фазе созданы дефекты механического смещения обмоток. Две другие фазы имеют исправное состояние. При помощи специальной схемы трансформатор включался в сеть. С помощью электронного осциллографа Tektronix типа TDS-2012 осуществлялась регистрация напряжения на первичной обмотке и сигнала отклика с одноименной фазы вторичной обмотки. Измерения повторялись для двух других фаз по такой же схеме. Результаты. На реальном трансформаторе типа НТМИ-6 экспериментально исследована и установлена принципиальная возможность осуществления контроля механического состояния его обмоток при использовании отклика напряжения на вторичной обмотке трансформатора при включении трансформатора в сеть. Таким образом, показано, что при включении трансформатора в сеть подключаемое напряжение может служить диагностическим импульсом, пригодным для зондирования механического состояния обмоток трансформатора по методу низковольтных импульсов.

MODELING AND MONITORING OF THERMODYNAMIC PROCESSES IN SYNCHRONOUS ELECTRIC MOTORS

Methods are given for the mathematical description of thermodynamic processes in the insulation of drive motors of alternating current megawatt class. The paper presents the requirements for equipping monitoring systems of the main technological equipment and electric machines, in particular, which regulate the monitoring of working capacity, reliability and safety of equipment using reliable technical and software tools. The most appropriate when choosing a monitoring model for synchronous motors is a functional diagnostic model, when using which the input actions of elementary checks are determined in advance by the working algorithm of the object, and only the composition of the controlled parameters of the diagnostic object is subject to selection. For a predictive analysis of the temperature of the windings of a synchronous machine, a three-stage heating theory is used, in which the motor is divided into a stator winding, a steel structure of the stator and a rotor. In addition, the models take into account the mechanical loads acting on the insulation of the stator windings in various modes during operation: electrodynamic, vibrational and thermomechanical. The results of the analysis of the dynamics of thermodynamic processes in the stator windings of machines with refinements related to the effects of cooling methods, the finning of the external surface of the machine, the heat sink through the frame and bearing shields, as well as the influence of a significant amount of air inside the thermal circuits of synchronous motors. For engineering calculations, algorithms for determining electrodynamic forces are recommended, taking into account simplifying assumptions that do not affect the accuracy of the practical assessment of the forces acting on the isolation of powerful machines. The determination of only some of the main components of the effects, which include the forces caused by the interaction of currents of one phase and acting on the extreme rod of the phase group in the involute part of the rod along the corresponding curves, is also justified.

Influence of the shape of the excitation pulse on the power and speed indicators of linear shock electromechanical converters of induction and electrodynamic types

Purpose. To study the effect of vibrational-damping, half-wave and aperiodic excitation pulses on the power and speed parameters of a linear shock electromechanical transducer (LSET) of induction and electrodynamic types when operating in idle, load and braking modes. Methodology. To account for the interconnected electrical, magnetic, mechanical and thermal processes, as well as a number of nonlinear dependencies, a mathematical chain model with lumped element parameters is used. This model allows you to quickly carry out the calculation of indicators and characteristics of the LSET with varying the shape of the excitation pulse and the operating mode. Results. The electrical and mechanical characteristics, power and speed parameters of the induction and electrodynamic type LSETs are obtained upon excitation of a vibrationally damped, half-wave and aperiodic excitation pulse when operating in idle, load and braking modes. Originality. It is shown that the highest speed indicators occur in idle mode, when the armature winding accelerates without an actuator, and the highest power indicators - in braking mode, in which the armature is stationary. Practical value. It has been established that the highest speed (18.95 m/s) is developed by an electrodynamic type LSET excited by single-half and vibrationally-damped pulses in the idle mode. The highest efficiency (29.2%) is developed by an electrodynamic type LSET upon excitation by a half-wave pulse in idle mode. The largest magnitude of the pulse of electrodynamic forces (19.2 N∙s) is developed by an induction-type LSET in braking mode. The largest excess of the temperature of the inductor winding (1.7 K) occurs in the LSET of the induction type in idle mode, and the largest excess of the temperature of the armature of the armature (0.7 K) is in the LSET of the electrodynamic type in braking mode.

Shape optimization of soft magnetic composite inserts for electromagnetic stirrer with traveling magnetic field

Purpose The purpose of this paper is to search optimal shape of soft magnetic composite-based inserts used to compensate the working gap between the liquid metal and the induction stirrer in metallurgical installations. Design/methodology/approach The study was based on numerical simulation of electromagnetic processes in frequency domain. To optimize inserts shape, the Nelder–Mead method was used. The maximum of integral electrodynamic force along x-axis was chosen as the objective function. All simulations were performed in finite element software package Comsol Multiphysics. Findings Optimal inserts shape was determined, at which the value of integral electrodynamic force along x-axis increased by 20% from 692 to 792 N. Originality/value Magnetic concentrators based on soft magnetic composite materials have long been used in high-frequency systems; at the same time, their use in low-frequency systems has not been previously considered in detail. The study of the shape effect of concentrators on the effectiveness of electromagnetic field in a liquid metal in a three-dimensional formulation was carried out for the first time.

Casimir force

Casimir force in quantum electrodynamics is the representation of zero point energy of vacuum. Depending on the type of fluctuation medium, generalized Casimir force covers a wide spectrum of topics in physics, such as, quantum, critical, Goldstone mode, and non-equilibrium Casimir force. In general, long range correlated fluctuations and constraints are two conditions for generating the Casimir force. In this paper, through a survey of the development of Casimir physics, we discuss several types of Casimir forces and several regularization methods. We end the paper with an outlook for the further development of Casimir physics in the future.

Электродинамические силы, действующие на контур с током в поле соленоида при его перемещении вдоль оси

The advisability of using expressions for the mutual inductance coefficients and electrodynamic forces of interaction in a system of circular solenoids and loops with a common axis that were obtained previously from an analytical study is shown on particular examples. The numerical results obtained from the expressions representing the mutual inductance coefficients in the form of written series are compared with the other known recommendations involving the use of tables or graphs. An expression for theelectrodynamic force of interaction between the loop and a solenoid with current is presented, and dependences for them constructed for different positions of the loop along the solenoid axis are given.

Research on simulation calculation on short-circuit electrodynamics force of power transformer winding

The safety and reliable operation of power grid is directly related to the ability of power transformer to withstand short-circuit, therefore, it is a problem to be solved to improve the ability of large power transformer windings to withstand short-circuit. Taking a three-phase five-limb power transformer as an example, the transient electromagnetic field, short-circuit electrodynamics force of windings and mechanical strength of coils are analyzed in depth. Firstly, the three-dimensional finite element model of the prototype is established, and the magnetic flux density distribution of the three-dimensional transient electromagnetic field of transformer under short-circuit operation and the axial and radial static force magnitude of the winding are calculated by using the field-circuit coupling method, and the distribution law can be obtained. At the same time, the mechanical strength of power transformer winding in its height direction is discussed, and the modal vibration mathematical model of transformer low-voltage winding in Z-axis direction is established. The displacement change and resonance frequency of the winding wire cake in the axial direction caused by short-circuit are calculated, and the short-circuit electrodynamics force of the winding is also checked. The research in this paper provides a theoretical basis for strengthening the design of short-circuit withstanding capacity of windings, and has a certain theoretical and engineering application value.