Number Of Windings Research Articles

Analytic models of magnetically enclosed spherical and solenoidal coils

We provide analytic solutions of the net magnetic field generated by spherical and solenoidal coils enclosed in highly-permeable, coaxial magnetic shields. We consider both spherical and cylindrical shields in the case of the spherical coil and only cylindrical shields for the solenoidal coil. Comparisons of field homogeneity are made and we find that the solenoidal coil produces the more homogeneous field for a given number of windings. The models are useful as theoretical and conceptual guides for coil design, as well as for benchmarking finite-element analysis. We also demonstrate how the models can be generalized to explore field inhomogeneities related to winding misplacement.

SQUID microscopy for mapping vector magnetic fields

We mounted a vector-scanning superconducting quantum interference device (SQUID) sensor on a commercial SQUID microscope and successfully improved the sensitivity and spatial resolution of the sensor. Our proposed vector 3D SQUID sensor used multilayered niobium (Nb)-based technology; we realized three SQUID sensors in the structure of a vector pickup coil system on a single chip. The vector pickup coil system was built with three pickup coils that were orthogonal to one another to obtain the X, Y, and Z components of a magnetic field vector. To improve both sensitivity and spatial resolution, we attempted to reduce the inner diameter by increasing the number of windings of the pickup coils using the multilayered Nb process. The design value for the dc SQUID sensors was either the critical current density Jc = 320 A cm−2 for two Josephson junctions (JJs) or the critical current Ic = 12.8 μA for the 2 μm × 2 μm JJs. To measure the current–voltage (I–V) and voltage–flux (V–Φ) characteristics of a sensor, we constructed a homemade measurement system. The fundamental characteristics of our SQUID sensors were in good agreement with the design parameters. We mounted our vector SQUID sensor on a commercial scanning SQUID microscope (SQM2000, Seiko Instrument Inc.) with a single flux-locked loop channel to test one of the three channels. We repeated the measurements three times to obtain the X, Y, and Z componential images of the magnetic field from a single vortex, and we synthesized the 3D mapping of the magnetic field vectors from a single vortex. We proved that our sensor mounted on a SQUID microscope was suitable for measuring the X, Y, and Z components of a vector magnetic field.

Analytical model for the equivalent impedances of the domestic induction heating system with rectangular cross‐sectional windings

This study proposes an analytical model to evaluate the equivalent impedances of domestic induction heating systems. The method of separation of variables is employed to determine the vector potential produced by a filamentary coil under a semi-infinite conductor. Then, based on the superposition principle of linear problems, the total vector potential of the coaxial, coplanar, connected-in-series rectangular cross-sectional multi-windings with same thicknesses, which are made of enamelled Litz wire, is derived by integrating the vector potential of filaments. Finally, the total voltage on the windings and the equivalent impedance of the induction heating system are obtained. The proposed analytical method is flexible to be used for calculating the equivalent impedance of multi-windings with any number of windings in an induction heating system with any mixture of windings with different lengths in the radial direction, and any distance between two adjacent windings in the radial direction. The proposed generally analytical method is successfully verified by comparison with the finite element method and shows improvement with respect to the conventional analytical method.

THE LOW ROTATION 1 PHASE AC GENERATOR USING MULTIPLE STATOR AND ROTOR METHOD IN THE FLOATING-HYDRO POWER PLANT

Abstract — Electrical energy is the most vital necessity in daily human’s life. The need of electrical energy has been continuously increasing along with the industry and society development. Indonesia is a tropical country with loads of energy sources which one of them is the new renewable energy sources. There are still many unexploited river flows that possess potentials as energy sources. The Floating-Hydro power plant is one of portable power plants harnessing the river flows as the energy source. In this study, the Low Rotation 1 Phase AC Generator Using Multiple Stator and Rotor Method in the Floating-Hydro Power Plant was designed. This generator consisted of several stators and rotors. The stator was strung together using the enamel wire. As in accordance to the design outcome, the number of stator windings was 364 per coil, the space between windings was 4cm, and the stator diameter was 25cm. Meanwhile, the rotor consisted of Neodymium (NdFeB) type permanent magnet which was going to be induced into the stator. Every rotor consisted of 10 pieces of permanent magnet with a space between magnets was 2cm. The experiment result, which was performed on the 1 phase axial generator using 2 stators and 3 rotors with loads in the form of 3 pieces of 35W 12VAC lamps, generated voltages of 2,1 VAC with currents of 0,03A at the low speed of 100rpm. Meanwhile, at the speed of 1200rpm, it generated voltages of 10,68VAC with currents of 0,23A. DOI : https://doi.org/10.26905/jeemecs.v2i2.3205

A Series-Connected Multilevel Converter: Topology, Modeling, and Control

Cascaded H-bridge (CHB) is a promising topology for medium-voltage high-power applications. CHB consists of low-power H-bridge modules in each phase, and these modules are connected in a cascade manner to achieve multilevel operation. However, CHB requires a phase-shifting transformer with multiple secondary windings to generate an isolated dc source for each module, and this requirement increases the overall system cost. In this paper, a series connection of low-power modules is employed to realize a new power converter called a series-connected multilevel converter. Each phase of the proposed topology requires a single isolated dc source. Hence, the required number of secondary windings is considerably reduced. This approach also minimizes the complexity and cost of the overall system. The operation of the proposed topology is presented by using three-level neutral point clamped modules in each phase. Model predictive control (MPC) is employed to control the dc-bus capacitor voltage and output currents of the proposed topology. A discrete-time mathematical model of the proposed topology is also developed to predict the future behavior of control variables. The performance of the proposed topology with MPC is verified through MATLAB simulations and a scaled-down laboratory prototype.

Anomalous Slowdown of Polymer Detachment Dynamics on Carbon Nanotubes.

The "wrapping" of polymer chains on the surface of carbon nanotubes allows one to obtain multifunctional hybrid materials with unique properties for a wide range of applications in biomedicine, electronics, nanocomposites, biosensors, and solar cell technologies. We study by means of molecular dynamics simulations the force-assisted desorption kinetics of a polymer from the surface of a carbon nanotube. We find that, due to the geometric coupling between the adsorbing surface and the conformation of the macromolecule, the process of desorption slows down dramatically upon increasing the windings around the nanotube. This behavior can be rationalized in terms of an overdamped dynamics with a frictional force that increases exponentially with the number of windings of the macromolecule, resembling the Euler-Eytelwein mechanism that describes the interplay between applied tension and frictional forces on a rope wrapped around a curved surface. The results highlight the fundamental role played by the geometry to control the dynamics and mechanical stability of hybrid materials in order to tailor properties and maximize performance.

A Lithium-Ion Battery Balancing Circuit Based on Synchronous Rectification

In this paper, a battery balancing circuit is proposed for the series-connected lithium-ion battery cells based on the principle of synchronous rectification. The proposed balancing circuit, also referred to as an equalizer, mainly includes a buck–boost converter (BBC), a multiport half-bridge converter (MHBC), and a driving circuit. The MHBC is coupled with a multiwinding transformer. Compared with the conventional congeneric methods, the number of transformer windings is almost reduced by half, leading to a more compact size and lower cost. Moreover, the secondary <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s of the MHBC are synchronously driven by the primary half-bridge converter (HBC) without the need of additional isolated <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> gate drivers and power supplies, dramatically reducing the circuit cost and complexity. In addition, the proposed equalizer can realize the module-to-multi-cell (M2MC) equalization under severe imbalance conditions to improve the balancing speed, and work at the any-cell-to-any-cell (AC2AC) self-balancing mode under slight imbalance conditions to improve the balancing efficiency and effectiveness, which achieves a good trade-off between balancing speed and effectiveness. The expressions of the equalization current and efficiency are derived and verified by experimental results. The proposed equalizer is experimentally evaluated for a string with 12 series-connected lithium-ion cells.

The performance of the modified pump motor as a generator on the Pump as Turbine (PAT) power plant

There are many types of the hydropower plant. Pump as Turbine (PAT) is one of the simple, practical and low-cost hydropower plants. In PAT technology, a commercial pump available in the market can be modified to become a PAT power plant. This paper is a technical note that describes the guideline to modify the induction pump motor into a generator and analyze the performance of the generator. There are two aspects that must be considered in modifying the motor, namely the motor construction and the output power. In modifying the motor pump, the magnet must be inserted in the rotor. Meanwhile, the wire diameter and the number of winding in the stator are modified to increase the voltage working range. The experimental tests were performed with a laboratory scale PAT power plant to identify the generator performance. The analysis showed that a modified pump motor generated 32.5 VAC and 0.33 Ampere of electrical power (10.725 Watt), only with 2.5 m of water head. The electrical power generated could be improved with a higher water head.

Optimasi Permanen Magnet Synchronous Machine Berbasis Firefly Algorithm

Magnets always have two poles namely the north pole (north / N) and the south pole (south / S). Just as the magnetic charge of the same magnetic pole repels - rejects and the different magnetic poles pull together. Magnets force magnetic materials such as iron due to the magnetic field. A permanent magnet generator is one of the electric machines that utilize mechanical forces to produce electricity where the generator utilizes a permanent magnet as its rotor. To obtain greater output power can be by changing the number and size of windings, varying neodymium permanent magnets of a certain size and reducing the rotor distance with the stator, so that greater power can be achieved. In this study comparing the design without control, with the PID controller, and with the PID controller detuning with Firefly Algorithm. From the simulation results it was found that the best controller in this study was PID-FA with the best current profile and the best voltage profile with a value of 698.3 rpm at t = 0.0055 seconds and steady state voltage at 700.3 rpm at t = 0.04 seconds.

Compact bulk-machined electromagnets for quantum gas experiments

We present an electromagnet combining a large number of windings in a constrained volume with efficient cooling. It is based on bulk copper where a small pitch spiral is cut out and impregnated with epoxy, forming an ensemble which is then machined at will to maximize the use of the available volume. Water cooling is achieved in parallel by direct contact between coolant and the copper windings. A pair of such coils produces magnetic fields suitable for exploiting the broad Feshbach resonance of ^66Li at 832.2\,832.2G. It offers a compact and cost-effective alternative solution for quantum gas experiments.

Induction voltages square and triangle solenoid as alternatives electrical energy resources

Solenoids have been made with square and triangular cross-sections. Both kinds of solenoids are made with an iron core and without an iron core. The solenoids specification were 12 cm long and 3.5 cm wide with 220 windings and 900 windings. The iron core specification was 12.5 cm long and 8 mm diameter. The induction voltages both of solenoids have calculated with experiments method in the laboratory. Calculation of induction voltages with the experiment method used the motor as the magnetic drive, full-wave rectifier circuit, neodym magnet, and led lamp. Induction voltage and electric current obtained of each solenoid for range from two cm until ten cm. The closest distance between the solenoid with the motor as magnetic drive and the greater the number of solenoid windings produced the greater the induction voltages. Triangular-sided solenoids with 220 windings produced faster induction voltages than the square-sided solenoid for the same number of windings. While an iron core solenoids produced faster induction voltages than solenoid without an iron core.

Enhanced Bandwidth Nonlinear Resonance Electromagnetic Human Motion Energy Harvester Using Magnetic Springs and Ferrofluid

An enhanced bandwidth nonlinear resonant electromagnetic energy harvester has been designed to harness low frequency energy from basic human motions. The inertial mass of the proposed harvester is formed by four stacked ring permanent magnets (PMs), which is suspended axially by two magnetic springs and circumferentially by ferrofluid within a carbon fiber tube. The magnetic springs are made up of two button PMs adhered, respectively, to the end cap at each end of the carbon fiber tube to provide varying repulsive forces to the PM stack, resulting in enhanced resonance frequency band and higher efficiency in energy harvesting. The ferrofluid that self-assembles around the edges of the PM stack acts as its bearing system to minimize frictional losses during its movement. Copper wire is wrapped outside the tube to form the armature winding. The stiffness characteristic of the magnetic springs and the optimum equilibrium position and number of windings have been determined by finite element method analysis. As a proof of concept, a portable prototype of the proposed energy harvester that weighs 110 g and with a volume of only 37.7 cm $^3$ is fabricated. A series of experiments is carried out and the results show that the frequency band of the harvester becomes wider as the external vibration intensity increases. In addition, the effectiveness of ferrofluid in reducing friction is demonstrated under walking and running conditions. Without ferrofluid, the maximum average outputs are 10.15 and 32.53 mW, respectively, for walking and running. With ferrofluid, the maximum outputs are 17.72 and 54.61 mW, representing an increase of $74.58\%$ and $67.88\%$ , respectively. Furthermore, the prototype exhibits an average power density of 1.45 mW/cm $^3$ during running motions, which compares favorably with existing harvesters used in low power wearable devices.

Design, modelling, and implementation of a modified double‐switch flyback‐forward converter for low power applications

This study proposes a modified double-switch flyback-forward (DSFF) converter for low-power applications with a reduced number of windings in its transformer. This circuit has resulted from the combination of the two-switch flyback and two-switch forward converters. It includes a simple transformer with one set of secondary side windings, and it is not necessary to design two separate sets of windings for the desired output voltage which is the main problem of other flyback-forward converters. An auxiliary winding has been designed for self-biasing, and consequently, it improves the overall efficiency in the no-load condition. Due to the modifications on the previously presented two-switch flyback-forward converter, the circuit model has changed. This study, first, analyses the operation of the proposed converter in detail, then it explains a method to design this converter in continuous inductor current mode. Also, a start-up voltage regulator circuit and a modified bootstrap gate driver will be investigated, and the DC and AC model of the converter will be presented. Experimental results validate the proposed DSFF converter. The tested circuit includes a DSFF converter, a pulse generator circuit, a start-up voltage regulator, and a modified bootstrap gate driver.

Comparative Study between Sliding Mode Control and the Vectorial Control of a Brushless doubly fed induction generator

Brushless doubly fed induction generators (BDFIG) show commercial promise forwind-power generation due to their lower capital and operational costs and higher reliability ascompared with doubly fed induction generators. This paper proposes a robust sliding mode control of grid-connected brushless doubly fed induction generator (BDFIG). The developed algorithm is based on the decoupling control by using oriented grid flux vector control strategy. The decoupling of the active and the reactive stator powers insures an optimal performance of the BDFIG at the sub-synchronous region. The stator of this machine incorporates two sets of three phase windings with different number of poles, power winding (PW) and control winding (CW). The proposed method is tested with the Matlab/Simulink software. Simulation results illustrate the performances and the feasibility of the designed control.

Electromagnetic Forming Analysis of the Al 99.0 Sheet with Tools of Different Configurations

Electromagnetic forming is an advanced manufacturing procedure, characterized by the fact that the tool carrying the deformation force does not touch the workpiece. This paper presents research regarding the electromagnetic forming of Al 99.0 (EN AW-1200) sheet with coils, having different configurations. The purpose of the research was to find the flat spiral coil configuration that ensures maximum deformation of the workpiece. Flat spiral coils with different gaps between the coil and the workpiece, and coils with different number of windings were tested. The influence of these parameters was monitored on the maximum strain of the free bulged parts. The analysis of the results obtained for different configurations of the flat spiral coils allowed the selection of the significant parameters that influenced the electromagnetic forming process of the Al 99.0 flat workpiece, which aimed to elaborate the mathematical model and to optimize the investigated process.

Influence of Adjacent Teeth Magnet Polarities on the Performance of Flux Reversal Permanent Magnet Machine

This paper provides a comprehensive analysis of performance difference among various kinds of flux reversal permanent magnet (FRPM) machines having different permanent magnet (PM) arrangements. Four PM arrangement types are, first, identified by the number and relative polarities of PMs on the stator teeth, and their influence on the equivalent pole-pair number of the armature winding and working harmonics of the air-gap field is revealed. Then, the torque variation against the rotor pole number of each PM arrangement is analyzed. The electromagnetic performance of four PM arrangements with a 14-pole rotor is compared in detail. It shows that the FRPM machine, in which four PM pieces are mounted on each stator tooth and two adjacent magnets on different stator teeth are of opposite polarities, offers the highest torque density and the highest efficiency, which make it promising in low-speed high-torque applications. In addition, four prototype machines are manufactured and tested to validate the findings.

Nonlinear Numerical Modeling of the Wire‐Ring Net for Flexible Barriers

To investigate the nonlinear mechanical behavior of the wire‐ring net, this paper presents a new numerical model that can collectively consider equivalence between numerical and actual wire rings. Quasi‐static tests, including tensile tests on steel wires and one‐ring specimens, and puncturing tests on net specimens were conducted. Based on the test results, the axial constitutive curves of steel wires were obtained. The linear correlation equations for the breaking loads of the one‐ring specimens and the puncturing strength of wire‐ring nets were established, both of which were related to the number of windings. The wire rings were modeled via an equivalent structure with a single winding and a circular cross section. Equivalence between the numerical and actual wire rings in terms of bending and tensile strength, total mass, contact with sliding friction, and rupture behavior were also derived and presented. In particular, the emphasis was on simulating the flattening effect, a phenomenon rarely accounted for in conventional numerical models. All dominant factors were reflected in a model with the material law by the input of material parameters. The proposed mechanical model was calibrated and verified by the data from the tests of the wire‐ring net. The calibrated mechanical model is also shown to successfully simulate a full‐scale test of a flexible rockfall protection barrier according to the ETAG027 standard.

Analysis and Optimization of Multi-Winding Toroidal Inductors for Use in Multilayered Technologies

The aim of this paper is to compare the performance of planar toroidal inductors and circular spiral inductors in multilayered technologies, in terms of achievable inductance density. New multi-winding toroidal inductor geometry is proposed to cover as much of the integration area as possible with the component footprint. The optimization of planar multi-winding toroidal inductors in multilayered substrates is investigated theoretically, and closed formulae are derived for their inductances as a function of geometrical parameters for any given value of the number of windings in the coil. The model obtained is validated experimentally and through electromagnetic simulation. Comparing the inductance of multi-winding toroidal inductors and compact spiral inductors allows us to update previously reported selection rules for the most suitable topology that leads to the most compact design.

Undressing confining flux tubes with TT¯

Lattice QCD simulations provide crucial information about the worldsheet dynamics of confining strings (flux tubes). An accurate extraction of the worldsheet $S$-matrix from lattice spectra requires accounting for polarization effects. Approximate integrability of the low energy worldsheet theory makes it possible to apply the Thermodynamic Bethe Ansatz to incorporate polarization effects at all orders in the number of windings and at the leading order in the derivative expansion. However, a systematic application of this technique in the presence of non-integrable effects and for multiparticle states becomes increasingly challenging. We point out that a recently understood equivalence between gravitational dressing and $T\bar{T}$ deformation provides a fully systematic and straightforward recipe to incorporate the leading polarization effects in the presence of an arbitrary inelasticity and for any number of particles. We illustrate this technique with several examples.

Failure analysis on over-temperature combustion of transformers in 4 MW offshore wind turbines

Abstract Wind power is one of the prevailing types of renewable energy, but the reliability of its components is always challenged by the severe service environment, especially on the offshore. Hence, case studies on failed components deserve to be publicly reported for experience sharing and failure prevention. In this event, severe degradations like combustion and abnormal electrical resistance rise were frequently detected on a large number of windings and lead bars within the transformers in 4 MW offshore wind turbines. To solve this problem, a series of characterization methods were utilized to investigate the assembly structure, matrix materials and macro/microscopic morphologies of the failed transformers. Temperature simulation experiment was also carried out to evaluate the normal operating conditions. The analysis results showed that risky factors induced from inappropriate installation, unreasonable design, unqualified fabrication and improper maintenance were the root causes for the failure. Finally, relevant mechanisms were discussed in detail and specific countermeasures were put forward.