Electrodynamic Forces Research Articles

Determination of Electrodynamic Forces between Coaxial Coil Turns with Current of Various Configuration

Determination of electrodynamic forces, as may be required for various practical purposes, is based on known calculation recommendations for mutual inductance coefficients, including the calculation methods with special functions, like complete elliptic integrals of the 1st and the 2nd kind, as well as spherical Legendre functions of the 2nd kind with half-integer index [1–5]. Some examples of practical tasks requiring these calculations are the assessments of mutual inductances in non-contact chargers, as well as the assessments of electrodynamic interactions in the windings of transformers, inductors, various solenoid-based loading devices, electric drives, etc. These applications are discussed in numerous publications and guides, e.g. [6–9].

Experimental Verification of Passive Axial Electrodynamic Suspension in a Bearingless Motor

This article investigates a bearingless motor with passive electrodynamic axial suspension. The axial suspension force is generated by a specific coil configuration called a figure-eight coil. Radial directions and tilting angles are stabilized by passive permanent magnet bearings. Since axial electrodynamic force increases with rotational speed, it must overcome a certain minimum threshold speed to compensate for the rotor weight and the unstable axial force caused by the permanent magnet bearing. Theoretical equations are derived for the braking torque caused by the suspension current and for the steady-state axial equilibrium position at constant rotational speed. A method based on the braking torque equation is proposed for correcting the mismatch between the magnetic center of the bearingless motor and the middle point of the axial clearance. This method sets the middle point between upper and lower touchdown positions in the same place where the motor current is minimum during passive axial suspension. Axial suspension is confirmed in the experiment with a noncontact laser sensor.

Анализ возникновения бросков магнитного потока и намагничивающего тока при включении трансформатора на холостом ходу

This article discusses the transients that occur in power transformers when they are turned on at idle. The main negative consequences arising from magnetizing current surges and their impact on the quality of electrical equipment, in particular, false alarms of relay protection devices and deformation of transformer structural elements by electrodynamic forces, are given. The mathematical derivation of physical quantities determining the process of occurrence of magnetic flux and magnetizing current surges is presented on the example of switching on a power single-phase transformer in idle mode. As a result of mathematical analysis, the main factors affecting the flow of the transient process when the power transformer is switched on in idle mode were identified. A mathematical expression was obtained that allows determining the phase of the mains voltage for a favorable moment of switching on a single-phase transformer, depending on the magnitude of the residual magnetic flux in the steel core of the transformer. Based on the analysis of transients that occur when transformers are switched on at idle, methods or algorithms for switching on power transformers can be developed that allow for a smooth start of the transformer and avoid or minimize negative consequences.

Characteristic Analysis of Coreless-Type Linear Synchronous Motor With the Racetrack Coils as Secondary for EDS Maglev Train

The characteristics of coreless-type linear synchronous motor, which is applied in the propulsion system of electrodynamic suspension maglev train are calculated and analyzed by the more accurate analytical model. First, the magnetomotive force distribution model of the vehicle coils is proposed according to their racetrack shape. Then, on the basis of the space harmonic method, the characteristic analysis formula of coreless-type linear synchronous motor with single-layer and double-layer armature winding are presented. Second, the air-gap flux density, back electrodynamic force, and thrust of the coreless-type linear synchronous motor are analyzed by the three-dimensional finite element simulation method and the analytical methods. Then, the relationship of efficiency, power factor, and power angle with the number of feeder units is obtained. Finally, the accuracy of the analytical model and numerical result are experimentally validated by comparing with the transient operation data on Yamanashi and Miyazaki test line.

РОЗРАХУНКОВА ОЦІНКА ВІБРОПЕРЕМІЩЕНЬ І МЕХАНІЧНИХ НАПРУЖЕНЬ ІЗОЛЯЦІЇ ЛОБОВОЇ ЧАСТИНИ ОБМОТКИ СТАТОРА ПОТУЖНОГО ТУРБОГЕНЕРАТОРА

Presented are the results of numerical studies of the distribution of vibration displacements and mechanical stresses in the insulation of the frontal part of the stator winding of a powerful turbogenerator under the influence of electrody-namics forces for different constructive solutions of the groove fastening of the winding rods in the end zone of the gen-erator stator core. Modeling of mechanical processes is carried out using the finite element numerical method (FEM) in a two-dimensional setting. The possibility of improving the design with the aim of reducing the amplitude of oscillations of the front parts of the stator winding was considered. Ref. 16, fig. 7.

Foundations of Electromagnetism: A Review of Wilhelm Weber’s Electrodynamic Force Law

This article reviews the electrodynamic force law of Wilhelm Weber and its importance in electromagnetic theory. An introduction is given to Weber’s force and it is shown how it has been utilised in the literature to explain electromagnetism as well as phenomena in other disciplines of physics, where the force law has connections to the nuclear force, gravity, cosmology, inertia and quantum mechanics. Further, criticism of Weber’s force is reviewed and common misconceptions addressed and rectified. It is found that, while the theory is not without criticism and has much room for improvement, within the limitations of its validity, it is equally as successful as Maxwell’s theory in predicting certain phenomena. Moreover, it is discussed how Weber offers a valid alternative explanation of electromagnetic phenomena which can enrich and complement the field perspective of electromagnetism through a particle based approach.

Электродинамические силы между соосными плоскими катушками круговой формы

Object and purpose of research. Non-contact power transfer to various marine facilities. Subject matter and methods. The study relied on the methods of theoretical electric engineering. Main results. This paper gives analytical estimates for electrodynamic forces acting on inductively-coupled coaxial flat coils of circular shape. Conclusion. The study yielded the expressions for the electrodynamic forces in inductively coupled circular coils interfaced so as to perform non-contact power transfer.

The complex Maxwell stress tensor theorem: The imaginary stress tensor and the reactive strength of orbital momentum. A novel scenery underlying electromagnetic optical forces

We uncover the existence of a universal phenomenon concerning the electromagnetic optical force exerted by light or other electromagnetic waves on a distribution of charges and currents in general, and of particles in particular. This conveys the appearence of underlying reactive quantities that hinder radiation pressure and currently observed time-averaged forces. This constitutes a novel paradigm of the mechanical efficiency of light on matter, and completes the landscape of the optical, and generally electromagnetic, force in photonics and classical electrodynamics; widening our understanding in the design of both illumination and particles in optical manipulation without the need of increasing the illuminating power, and thus lowering dissipation and heating. We show that this may be accomplished through the minimization of what we establish as the reactive strength of orbital (or canonical) momentum, which plays against the optical force a role analogous to that of the reactive power versus the radiation efficiency of an antenna. This long time overlooked quantity, important for current progress of optical manipulation, and that stems from the complex Maxwell theorem of conservation of complex momentum that we put forward, as well as its alternating flow associated to the imaginary part of the complex Maxwell stress tensor, conform the imaginary Lorentz force that we introduce in this work, and that like the reactive strength of orbital momentum, is antagonistic to the well-known time-averaged force; thus making this reactive Lorentz force indirectly observable near wavelengths at which the time-averaged force is lowered. The Minkowski and Abraham momenta are also addressed.

An active metamaterial cell concept for nonreciprocal vibroacoustic transmission

The challenge of inducing stable and robust nonreciprocal transmission of sound is seen as an important milestone on the path towards developing active acoustic metamaterials. Structures that can transmit sound or vibration in a nonreciprocal manner may be considered analogous to an electrical diode and could be useful in many applications, such as noise control and the development of invisible acoustic sensors and acoustic cloaking. This paper focuses on conceptual development and experimental validation of an active metamaterial cell that does not obey the reciprocity principle. The structural cell considered, when activated, significantly attenuates vibration transmission through it in one direction and increases it in the opposite direction. The effect is present in a broad frequency band. The loss of reciprocity is induced by using two concurrent velocity feedback loops with non-collocated sensor-actuator pairs. Inertial accelerometers with time-integrated outputs are used in conjunction with miniature electrodynamic force actuators. The study is first carried out theoretically, using an electromechanically fully coupled lumped parameter model of an otherwise flexible active structure. The derived model is used to conduct analysis of the control system stability and performance. Given that a non-collocated transducer arrangement is considered, special attention is paid to the selection of parameters of the passive system which ensure satisfactory gain margins when the system is made active. In fact, criteria for unconditional stability are derived analytically, in terms of two simple inequalities for the system with idealised sensor-actuator pairs. For realistic transducers, however, unconditional stability is not possible. Nevertheless, if the two inequalities are respected, useful gain margins of the active system can be expected. This is validated experimentally using a dedicated 3D-printed measurement test rig. A substantial reduction of vibration transmission in the desired direction, accompanied by an increase in the opposite one, is recorded experimentally. These results suggest that the control scheme proposed could be used to design an active acoustic metamaterial, which would enable the significantly different transmission of sound depending on the direction it enters such a system.

A Trolley Wire De-Icing System

This paper presents a dedicated system for de-icing trolley wires. The proposed issue is appropriately under the protection of intellectual property for solving as described in patent no.B1 230665 PL in the Patent Office of the Republic of Poland. In the solution presented herein, de-icing is achieved mainly by electrodynamic force excitation and secondarily as a result of heating. Because ice is removed primarily through vibrations, it avoids a large consumption of electricity associated with the high specific heat of water. More importantly, operation is nearly simultaneously applied to the total distance of the trolley power grid between two substations. For this reason, it requires less electricity consumption and less time to apply than in heating, mechanical, or chemical methods.

Turbogenerator Electromagnetic Analysis with Changing Reactive Load

Comparative numerical analysis of electromagnetic processes in the end zone of powerful turbogenerators has been carried out at changes in reactive load from rated duty to underexcitation, as well as performance parameters of static overload that determine the stability of synchronous operation of turbogenerators in the power system. It was demonstrated that the representation of magnetic field sources and calculation results in the form of rotating waves allows simplifying and speeding up the solution of threedimensional electromagnetic problems in the turbogenerator end zone. Using a previously developed calculation method, the electromagnetic fields and processes in over- and underexcitation modes, in particular, peculiarities of shielding in turbogenerators are studied. It was established that the added losses and electrodynamic forces in underexcitation modes acting on the outermost core packages, pressure plate, and stator shield increased by 1.5–3.0 times, resulting in accelerated aging of the turbogenerator end zone. An appropriate margin shall be provided in the cooling system and the structural design of the turbogenerator end zone. Static overload capacity in nominal conditions is determined by the ratio of maximum power to rated power. An analytical functional relationship between static overload capacity and load conditions was established. It was demonstrated that when switching to the underexcitation mode while maintaining the active load due to a decrease in the excitation current and maximum power, the static overload factor decreases to unity, that there is virtually no static stability margin of the turbogenerator in this mode. Calculations were made for turbogenerators with a capacity of 200–1111 MVA. It is recommended to limit the operation of turbogenerators in underexcitation modes and to use specialized compensators more extensively.

Determination of Radial Forces Acting Between Coaxial Coils Located in the Same Plane

The electrodynamic forces acting between coaxial turns with current are estimated for the case when the turns belong to different layers in a multilayer coil, which are arranged in the same way. Expressions for the radial components of electrodynamic forces acting on a concentric outer turn are given. The suggested expressions are verified for consistency with the result obtained for the mutual inductance gradient in the radial direction, known from [1]. The expressions for tensile forces in the case of thin-layer disk coils based on their determination in terms of the inductance derivative with respect to the average radius are compared in two versions: with reference to Wheeler's approximating formulas for inductance, one of which is written in [2], and the other in [3]. The article may be useful for specialists dealing with evaluation of inductances and electrodynamic forces in the live parts of electrical systems.

Строгие и приближенные выражения для коэффициентов взаимной индукции и электродинамических сил соосных витков и плоских (дисковых) катушек с током

Object and purpose of research. The paper is concerned with the mutual inductance coefficients of co-axial circuits in a planar coil system. Known modifications for mutual inductance and electrodynamic forces in a system of co-axial circuits are written, and relations for their calculation are compared. Materials and methods. For this purpose the methods of mathematical physics and theoretic electric engineering are used. Main results. Alternative expressions are given for mutual inductance coefficients of co-axial coils and electrodynamic forces between the live coils. Curves of mutual inductance are plotted for planar coils with the distance between planes equal to 2 cm and the distance between coil turns Р equal to 1 сm and the distance between coil turns N equal to 0.5 сm, 0.4 сm & 0.3 сm. Conclusion. Relations have been derived for calculation of mutual inductance coefficients and electrodynamic forces at current passage in planar co-axial coils, which are very important for wireless transfer of power.

Experimental evidence for long-distance electrodynamic intermolecular forces - Supplementary Materials

Experimental evidence for long-distance electrodynamic intermolecular forces - Supplementary Materials

DYNAMIC PROCESSES ANALYSIS IN HIGH-SPEED SPINDLE ASSEMBLIES OF MACHINES TOOL WITH ACCOUNT DIFFERENT TYPES NONLINEARITY

The productivity and accuracy machine parts often depend on the dynamic processes during machine and cutting operation. The increase requirements for machining operation and quality machine parts leads to the need to evaluate and take into account all the capabilities of the technological processing system (TS) to ensure the stability of the cutting process and increase speed. One of the features emergence and existence of self-oscillating processes, the least studied and dangerous in terms of the effect on sustainability ТS is the nonlinearity parameters elastic system of the machine tool and the processes occurring during cutting operation. Therefore, to assess the conditions for implementation of the cutting process with a steady limited amplitude of oscillations, it is necessary to analyze and take into account the main nonlinearities dynamics of the TS. The article considers dynamic processes in high-speed processing systems on the example of high-precision spindle assemblies, with analysis and following review of their different types nonlinearity. The machine tool spindle unit for the case of high-speed processing according to the working conditions approaches the scheme of the rotor system which self-oscillations can be caused by the action of non-conservative circulation-type forces that are not associated with external periodic loads or any resonant relationships: internal friction forces, hydrodynamic forces in sliding bearings and seals, electrodynamic and electromagnetic forces in the electrical components of motor-spindles. It is shown that if the nonlinearity is associated only with internal external friction and coefficients of friction forces do not depend on frequency, the amplitude and frequency of self-oscillations (unlike linear system) will depend only on relationship of friction forces.

Experimental evidence for long-distance electrodynamic intermolecular forces.

Both classical and quantum electrodynamics predict the existence of dipole-dipole long-range electrodynamic intermolecular forces; however, these have never been hitherto experimentally observed. The discovery of completely new and unanticipated forces acting between biomolecules could have considerable impact on our understanding of the dynamics and functioning of the molecular machines at work in living organisms. Here, using two independent experiments, on the basis of different physical effects detected by fluorescence correlation spectroscopy and terahertz spectroscopy, respectively, we demonstrate experimentally the activation of resonant electrodynamic intermolecular forces. This is an unprecedented experimental proof of principle of a physical phenomenon that, having been observed for biomacromolecules and with long-range action (up to 1000 Å), could be of importance for biology. In addition to thermal fluctuations that drive molecular motion randomly, these resonant (and thus selective) electrodynamic forces may contribute to molecular encounters in the crowded cellular space.

Agent-based models for detecting the driving forces of biomolecular interactions

Agent-based modelling and simulation have been effectively applied to the study of complex biological systems, especially when composed of many interacting entities. Representing biomolecules as autonomous agents allows this approach to bring out the global behaviour of biochemical processes as resulting from local molecular interactions. In this paper, we leverage the capabilities of the agent paradigm to construct an in silico replica of the glycolytic pathway; the aim is to detect the role that long-range electrodynamic forces might have on the rate of glucose oxidation. Experimental evidences have shown that random encounters and short-range potentials might not be sufficient to explain the high efficiency of biochemical reactions in living cells. However, while the latest in vitro studies are limited by present-day technology, agent-based simulations provide an in silico support to the outcomes hitherto obtained and shed light on behaviours not yet well understood. Our results grasp properties hard to uncover through other computational methods, such as the effect of electromagnetic potentials on glycolytic oscillations.

Electrodynamic compensator for high-current contact devices

Compensators of electrodynamic repulsion forces of closed electrical contacts are designed to increase the stability of the operation of switching electrical devices when short-circuit currents flow. The possibilities of increasing the efficiency of electrodynamic compensators (one-loop and two-loop) in their traditional design are very limited. The paper analyzes an electrodynamic compensator for high-current contacts, in which the free end of the inactive contact included in the design of the compensator with contact pads is bent 180 degrees towards the axis of rotation of the inactive contact. As a result of this, the shoulder, on which the electrodynamic force of repulsion of the contacts acts, decreases. In such a design, the moment of repulsion of the contacts will also be less and the fulfillment of the condition for its full compensation is facilitated. Formulas are given for calculating the additional electrodynamic force of the considered compensator and its contour coefficient. Calculations of the additional electrodynamic effort of the breaker compensator for a rated current of 630A with a short-time withstand current of 40kA have been performed. With the length of the bent part of the inactive contact equal to 25% of the total length of the current loop, the resulting electrodynamic force of the compensator increases by 4.69%. In this case, a 25% reduction in the torque that is repulsive to the contacts occurs.

RESEARCH OF THE PERFORMANCE INDICATOR OF AN ELECTROMAGNETIC MILL

The paper is devoted to the development of a way for quantitative evaluation of the performance of an electromagnetic mill, i.e. a device that converts electrical energy into energy of mechanical interaction of operating elements (millstones) with the substance being ground/mixed. The proposed way is based on processing the results of calculating the trajectories of ferromagnetic millstones of an electromagnetic mill moving in a rotating magnetic field under the action of electrodynamic forces and hydrodynamic resistance forces and limited by the space of the working chamber. The average values of the number of blows, the momentum of the force of these blows, the linear velocity of the millstones and the value of the jerk are calculated. The proposed expression for calculating the integrated non-dimensional performance indicator is calculated on the basis of the above values and allows to link the performance of the grinding process with the design indicators of the mill inductor, the size of its working chamber, quantity, shape, dimensions of millstones, etc. The results of mathematical experiments to determine this performance indicator for an electromagnetic mill with a working volume of 2090 cm3 and an average value of magnetic induction in the working chamber ≈ 0.12 T are specified. This way needs an experimental confirmation. References 11, figures 5, table 1.

Robust electrical contacts integrating a liquid metal bridge for mechanical switches

Intrinsic roughness of solid surfaces causes a series of inevitable shortcomings in the use of mechanical electrical contacts, among which one of the most fatal is the repulsive electrodynamic force arising from high currents. A large contact force coming from a heavy holding mechanism helps to suppress the repulsive effect whereas the mechanism consumes energy and remains to be challenging for a compact switching device. Here, a liquid metal (LM) bridge is introduced to wet solid electrodes to eliminate contact issues. Four instability patterns induced by the electromagnetic pinch effect are identified to characterize LM bridge’s response to high currents. Simulation results reveal that an inner vortex caused by uneven distributions of current density and electrodynamic volume force leads to the rupture of a necked LM bridge. With a uniform structure, a cylindrical LM bridge is proved to be robust with respect to an impulse current higher than 10 kA, exceeding a commercial compact relay by a factor of more than 10 in terms of current withstand performance. Our research facilitates compact and energy-saving switch equipment and has a potential to realize arbitrary desired levels of high current withstand without the use of a holding mechanism. This paper also offers deep insights into the high current applications of LM from the perspective of fluid related physical mechanisms.