Three-phase Arrangement Research Articles

Magnetic Resonance Imaging-Compatible Electromagnetic Actuator: Design and Tests

This paper presents the detailed design, construction and tests of a protype iron-free MRI-compatible electromagnetic actuator. The originality of this proposal lies in the use of the homogeneous static magnetic field B0, present in the MRI bore, to ensure the electromechanical energy conversion. The armature is composed of three rectangular coils in a three-phase arrangement, which makes the actuator very light-weight and compact. The operating principle is that of an AC synchronous motor with a rotating armature. In order to design the actuator, a 3D analytical electromagnetic model is developed to predict the magnetic field produced by the armature winding. Then, a 3D finite element (FE) computation is performed to validate the analytically calculated magnetic field. The developed analytical model is then inserted into an optimization routine based on Genetic Algorithms (GAs) to obtain the prototype dimensions to be realized. Finally, the prototype is constructed and tested inside an MRI research scanner. The results indicate that the reduction in the Signal-to-Noise Ratio (SNR) and the geometrical distortion are less than 5% when the actuator is powered with a current of 10 times the rated one and when it is located very close to the subject to be imaged.

Corner Transition Toolpath Generation Based on Velocity-Blending Algorithm for Glass Edge Grinding

Sharp corners usually are used on glass contours to meet the highly increasing demand for personalized products, but they result in a broken wheel center toolpath in edge grinding. To ensure that the whole wheel center toolpath is of G1 continuity and that the grinding depth is controllable at the corners, a transition toolpath generation method based on a velocity-blending algorithm is proposed. Taking the grinding depth into consideration, the sharp-corner grinding process is planned, and a velocity-blending algorithm is introduced. With the constraints, such as traverse displacement and grinding depth, the sharp-corner transition toolpath is generated with a three-phase motion arrangement and with confirmations of the acceleration/deceleration positions. A piece of glass with three sharp corners is ground on a three-axis numerical-control glass grinding equipment. The experimental results demonstrate that the proposed algorithm can protect the sharp corners from breakage efficiently and achieve satisfactory shape accuracy. This research proposed a toolpath generation method based on a velocity-blending algorithm for the manufacturing of personalized glass products, which generates the transition toolpath as needed around a sharp corner in real time.

Double three-phase PMSM structures for fail operational control

This paper deals with permanent magnet synchronous motors (PMSM) structures. Especially their double three-phase arrangements are analysed in detail. Comparison of three different structures is treated. Non-overlapping concentrated winding is the first analysed structure. Distributed winding arrangement with interlaced sub-systems and also distributed winding arrangement with segregated sub-systems follows.The behaviour of all motor structures during normal operation is the same but the properties during faults are different. The motor behaviour during active short circuit (ASC) is discussed. ASC of whole motor and also partial ASC tests were performed. Current waveforms in different operating points are compared. Results show differences of individual structures with respect to operation during fault.

The Three-Phase Structure of Random Butene-1/Ethylene Copolymers

Abstract The three-phase arrangement of random copolymers of butene-1 with ethylene was investigated and compared with isotactic poly(butene-1) homopolymer (iPB-1). In all the analyzed compositions, isothermal crystallization leads to a three-phase structure, made of one crystal phase and two amorphous fractions that differ in mobility: the mobile amorphous fraction (MAF), made of the polymer chains that relax at the glass transition, and a rigid amorphous fraction (RAF) made of the amorphous segments coupled with the crystal phase. Copolymerization with ethylene leads to a drop in crystal fraction and to a sizable increase of both the RAF, and of the specific RAF, i.e. of the RAF normalized to crystallinity. Analysis of crystal growth rate allowed quantifying the fold surface free energy, which increases of about 50 to 100% in the copolymers, compared to iPB-1 homopolymer. In the butene-1/ethylene random copolymers, ethylene units are mostly excluded from the crystals and accumulate at the crystal/amorphous interphase, thus affecting the rigid amorphous area. The varied composition and higher mobility of the rigid amorphous fraction of the copolymers affects also the Form II to Form I transformation of poly(butene-1) crystals, which occurs with enhanced kinetics in the copolymers, compared to iPB-1 homopolymer.

Effective property estimates for n-phase composites with from all to none co-continuous phases

Several papers from the author and co-workers have been dedicated in the last years to estimating effective properties of n-phase composite materials (∀n ≥ 2) with all phases being co-continuous. The proposed estimate started from an old literature on that point and several of the presented formal results provided new highlights for such phase architectures that are not accounted for by the classical homogenization schemes. By duality, the case when none of the n phases in such composites can be taken as an infinite matrix (all discontinuous phases, say) was also treated, with a general explicit form being given for a relevant effective property estimate. Disregarding multi-level phase arrangements, we here treat the arrangement that still has no estimate so far, in terms of effective properties from the general homogenization framework for micro-heterogeneous and macro-homogeneous media: the case with several (p) but not all (n) phases being co-continuous. This assemblage type exists from three-phase arrangements and becomes the most important in number from four assembled phases. The proposed estimate form is based on the determination of the appropriate properties to be given to a reference n+1 matrix phase with infinitesimal volume fraction for satisfying both the co-continuity of the p phases and the embedded nature of the n-p not continuous (included) ones. For more than two co-continuous phases and any number of included ones, these reference matrix properties are shown to result from solving an inverse problem. We provide, up to five co-continuous phases and for several material symmetry types of interest, an analytical solution for these reference matrix properties. We exemplify the results, holding for various (elastic- or dielectric-like, possibly coupled) properties and structure symmetries, for three continuous phases. With these results all possibilities of assembling n phases from all to none continuous ones have relevant theoretical estimates, as exemplified for n=3, including some comparisons with Finite Element calculations.

Investigation Into the High-Frequency Limits and Performance of Load Commutated Inverters for High-Speed Synchronous Motor Drives

Load commutated inverters (LCIs) are still widely used for their robustness and reliability in high-power synchronous motor drives, in either single or multiple three-phase configurations. A restriction to their use in high-speed applications is due to the criticalities of thyristor operation at high switching frequencies. The upper frequency limits of LCIs are usually addressed in the existing literature as something independent of the drive architecture. On the contrary, this paper highlights how the maximum frequency that can be safely attained closely relates to the number of LCIs that are used to supply the synchronous motor. In fact, moving from a single to multiple three-phase arrangements is proved to introduce more stringent frequency constraints due to the mutual interaction between stator windings during commutations. Frequency limits for safe operation of single- and multiple-LCI drives are derived in quantitative terms and experimentally assessed on a 2-MW synchronous motor fed by a couple of LCIs. Practical implications of such limits in the design of high-power high-speed drives are finally discussed.

New Metallographic Method for Estimation of Ordering and Lattice Parameter in Ternary Eutectic Systems

Ternary eutectics develop a rich variety of microstructures depending on the solidification conditions. This article describes a new procedure to analyze the three-phase arrangement in metallographic sections following solidification; this method provides a clear definition of both the interphase spacing and the degree of ordering. Distance and angle between the phase areas are calculated after determination of the centers of mass for each phase area. A polar plot of these data allows an easy determination of the spacing and the order. The new method is discussed with both experimental as well as simulated microstructure images. It is first tested on artificial phase arrangements, which are fully ordered, semi-ordered, or random.

Magnetic Eddy-Current and Thermal Coupled Models for the Finite-Element Behavior Analysis of Underground Power Cables

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We have modeled underground isolated power cables by using magnetic eddy-current (EC) and thermal coupled formulations solved by the finite-element method (FEM). The magnetic field equation expressed in terms of magnetic vector potential (MVP) is strongly coupled with the total current density equation, which includes the source and the EC densities for taking into account skin and proximity effects. The model uses the computed EC density of losses with electric conductivity temperature dependence introduced as a heat source in the free transient thermal equation completed by the convection heat transfer. We studied single and multicircuit three-phase arrangements at various cable spaces in order to analyze the magnetic flux density and the time-space temperature evolution. </para>

An in situ microscopic spectroelectrochemical study of a three-phase electrode where an ion transfer at the water|nitrobenzene interface is coupled to an electron transfer at the interface ITO|nitrobenzene

Coupled electron and ion transfer was studied at a three-phase arrangement where decamethylferrocene was dissolved in a droplet of nitrobenzene that was sandwiched between an optically transparent ITO electrode and a glass plate. The sandwiched droplet was surrounded by an aqueous electrolyte solution in which the auxiliary and the reference electrodes were positioned. The oxidation of decamethylferrocene was followed by in situ spectroscopy with the help of a spectrometer interfaced to an optical microscope. The fast progression of the reaction starting at the three-phase junction and advancing towards the middle of the droplet is explained on the basis of a simplified model that assumes a progressive activation of the working electrode|nitrobenzene interface due to the ingress of transferred anions and decrease of ohmic resistance inside the nitrobenzene phase.

Quantification of the chiral recognition in electrochemically driven ion transfer across the interface water/chiral liquid

The electrochemically driven transfer of the chiral anions of d- and l-tryptophan across the interface water/chiral liquid ( d- or l-menthol) is stereoselective, and it can be used to determine quantitatively the difference in Gibbs energies for the solvation of chiral ions in chiral liquids. The ion transfer can be achieved in a three-phase arrangement where a droplet of the chiral liquid containing decamethylferrocene as the electroactive redox probe is attached to a graphite electrode immersed in the aqueous solution containing the chiral ions.

Electromagnetic losses in a three-phase high temperature superconducting cable determined by calorimetric measurements

A 10 m long high temperature superconducting (HTS) cable conductor was placed in a plane three-phase arrangement. The test-bed enabled us to study the conductor losses for different separations between the phases. The superconductor was fixed symmetrically in the centre, whilst the two outer conventional phases (600 mm 2 Cu) could be moved in the plane. It was possible to vary the inter-phase distance (centre to centre distance) from 9 to 48 cm. The HTS cable conductor was placed in a stainless steel cryostat and cooled with flowing liquid nitrogen (LN2). The losses were determined using a calorimetric technique where the temperature increase in the flowing LN2 was measured with a set of thermo-couples. Results indicate that the total AC loss increases significantly when the separation between the conductors is reduced.

Reduction of iodine at the organic liquid | aqueous solution | graphite electrode three-phase arrangement

The electrochemistry of the iodine/iodide redox couple was studied at the three-phase arrangement organic liquid | aqueous solution | graphite electrode. A droplet of an organic solvent, e.g. nitrobenzene, containing dissolved iodine was attached to a graphite electrode and immersed in an aqueous electrolyte solution. The reaction mechanism has been studied in the presence of NO 3 −, Cl −, Br −, F − and ClO 4 − ions in the aqueous supporting electrolyte, and for nitrobenzene, tetrachloromethane, and paraffin oil as organic solvents for iodine. The reduction of iodine in the nitrobenzene droplet is either accompanied by a transfer of the iodide ions formed from nitrobenzene to water: (i) I 2(nb)+2e −⇄2I − (aq), or, in the case that the aqueous electrolyte is an alkali chloride or bromide, by a transfer of chloride or bromide ions from nitrobenzene to water: (ii) I 2(nb)+2X − (nb)+2e −⇄2I − (nb)+2X − (aq) (X −=Cl −, Br −, possibly in the form of I 2X −). The second reaction is possible because with chloride and bromide ions a rather fast reactive partition of the aqueous electrolyte into nitrobenzene occurs, due to the formation of I 2X − (nb) ions in nitrobenzene.

An electrochemical method for determination of the standard Gibbs energy of anion transfer between water and n-octanol

The transfer of the ions Cl −, Br −, I −, ClO 4 −, SCN −, NO 3 −, BF 4 −, and (C 6H 5) 4B − across the water| n-octanol (W|OC) liquid interface was studied and the standard Gibbs energies of ion transfer were determined. The ion transfer was achieved by oxidation of decamethylferrocene dissolved in a droplet of n-octanol that was attached to a graphite electrode immersed in the aqueous solutions of the respective alkali salts of the anions. The electrode reaction can be described by the equation: dmfc (OC)+X (W) −⇄dmfc + (OC)+X − (OC)+e −, where X − is the transferred anion. Square-wave voltammetry at this three-phase arrangement was utilised to determine the formal potential of the decamethylferrocene/decamethylferrocenium (dmfc/dmfc +) couple under the condition of ion transfer across the water| n-octanol interface. For calibration the standard Gibbs energies of ion transfer have been extrapolated to octanol from the series of known data for methanol, ethanol, n-propanol, and n-butanol. All these data are consistent and the experimental dependence of the formal potentials on the standard Gibbs energies is as predicted by theory. The validity of data is further supported by calculations of Gibbs energies of ion transfer using the Born theory. Until now it was not possible to perform electrochemical measurements at the water| n-octanol interface because in the conventional four-electrode cells this interface cannot be polarised. With the new method it is now for the first time possible to determine the Gibbs energies of transfer of ions across the water| n-octanol interface. These values are of very wide use for assessing the lipophilicity of compounds in chemistry, medicine, and pharmacology.

A multiphasic hollow fiber reactor for the whole-cell bioconversion of 2-methyl-1,3-propanediol to (r)-beta-hydroxyisobutyric acid.

This paper describes the bioconversion of 2-methyl-1,3-propanediol to (R)-beta-hydoxyisobutyric acid (HIBA) by Acetobacter ALEI in a hollow fiber membrane bioreaction system arrangement that allows the integration of three liquid phases: the aqueous bioconversion phase, the organic phase consisting of a solution of trioctyl phosphine oxide (TOPO) in isooctane, and the third phase consisting of a basic stripping solution that allows reextraction of HIBA from the organic phase. A comparison of HIBA mass transfer experiments was carried out in the membrane reactor with two and three phases for different pH and TOPO concentrations. The use of the three-phase arrangement allows the extraction of high quantities of HIBA from the aqueous medium (higher than 85%) independently of the pH, whereas in the two-phase system the percentage of HIBA extracted from the aqueous medium was lower, 42% in the best case, and strongly influenced by the pH. The percentage of the extractive agent TOPO in the organic phase influenced on the mass transfer rate in both bi- and triphasic arrangements. By simply integrating the re-extraction phase in the system it was possible to increase the extraction yield by 2-fold, reduce the amount of TOPO by 4-fold, and operate at the more favorable pH 4. A bioconversion experiment was done in these conditions (pH = 4, TOPO = 5%) to confirm the advantages of including the third stripping solution. Fed-batch operation of the triphasic membrane reactor was maintained for more than 20 h, reaching an HIBA concentration in the stripping solution of 29 g L(-)(1).

An automatic calibrator for wattmeters with harmonic analysis capability

This paper deals with a three-phase phantom-power generator, which is designed for calibrating digital wattmeters with harmonic analysis capability. The calibration of such instruments is a critical task due to the lack of suitable calibrators. Fortunately, the calibration procedure can be limited to the first harmonic components when digital wattmeters are employed to characterise electrical machines, so that also simple calibrator design can be adopted. This paper describes a three-phase calibrator arrangement which is able to generate an arbitrary spectrum up to 5 kHz and a phantom power variable up to 3 kVA per phase. The uncertainty on the power associated to the first harmonic components is of about 0.1% in nonsinusoidal conditions. The calibrator employs a Direct Digital Synthesis technique, so that a frequency change of the output signal can be obtained without modifying the sampling frequency. Such a technique also permits to generate the frequency modulated signals that are often encountered at the output of static power converters that feed electrical machines.

Current distribution in generator main connections

Heavy copper busbars are used to carry the current between turbogenerators and generator transformers in U.K. power stations. At each end of the busbars an arrangement of many flexible braided parallel interconnectors are used between the busbars, the generator and the transformer. Within such a group of parallel interconnectors, the electromagnetic interaction induces a non-uniform current distribution as a result of which uneven heating of braids may occur. The computer-oriented technique described predicts current distributions in three-phase arrangements of parallel rectangular conductors. The paper discusses theory and distributions in three-phase arrangements. Comparison of computed and experimental results, relating to two installations, is also included.