Method for the Analysis of Three-Phase Networks Containing Nonlinear Circuit Elements in View of an Efficient Power Flow Computation

The present paper is devoted to applying the Hănțilă method for solving nonlinear three-phase circuits characterized by different reactance values on the three sequences (positive, negative and zero). Nonlinear elements, which are components of the circuit, are substituted by real voltage or current sources, whose values are an iteratively corrected function of the voltage across or the current through them, respectively. The analysis is carried out in the frequency domain and facilitates an easy evaluation of the power transfer on each harmonic. The paper presents numerical implementations of the method for two case studies. For validation, the results are compared against those obtained using the software LTspice in the time domain. Finally, the power flow on the harmonics and the overall power balance are analyzed

Correlation between Magnetic Properties and Chemical Composition of Non-Oriented Electrical Steels Cut through Different Technologies

Due to worldwide regulations on electric motor manufacturing, the energy efficiency of these devices has to be constantly improved. A solution may reside in the fact that high quality materials and adequate cutting technologies should be carefully chosen. The magnetic properties of non-oriented electrical steels are affected by the cutting methods, through induced plastic, and thermal stresses. There is also an important correlation between chemical composition and different magnetic properties. In this paper, we analyze different industrial grades of non-oriented electrical steels, used in electrical machines’ core manufacturing as M800-65A, M800-50A, M400-65A, M400-50A, M300-35A, and NO20. The influence of the cutting methods on the normal magnetization curve, total energy loss and its components, and relative magnetic permeability is investigated in alternating currents using a laboratory single sheet tester. The chemical composition and grain size influence are analyzed and correlated with the magnetic properties. Special attention is devoted to the influence of the increased cutting perimeter on the energy losses and to the way it relates to each chemical alloy constituent. The final decision in what concerns the choice of the proper magnetic material and the specific cutting technology for the motor magnetic cores is imposed by the desired efficiency class and the specific industrial applications

Influence of mechanical and water-jet cutting on the dynamic magnetic properties of NO Fe-Si steels

Magnetization curve and energy losses have been analyzed in non-oriented (NO) Fe-Si alloys with variable thickness (0.20 mm–0.35 mm), cut at widths ranging between 5 mm and 60 mm, in order to assess the impact of cutting, either done by punching or water-jet techniques. Measurements were performed by means of a digitally controlled single strip tester, from dc up to 1.5 kHz, at peak polarization values Jp = 1.0 T and 1.5 T. The evolution of the magnetization curve and the structure-dependent hysteresis Wh and excess Wexc loss components have been assessed as a function of the strip width using a simple phenomenological model, by which the extension of the damaged area at the edges of the cut sheets is estimated. Such a model assumes a hyperbolic dependence of the measured polarization on the cut strip width

Effect of mechanical cutting on the energy loss of laser-scribed grain-oriented alloys

We investigate the effect of mechanical cutting on the magnetic properties of high permeability grain-oriented (HGO) laser-scribed Fe-Si sheets. Measurements have been performed on strips of different widths (5 to 60 mm) cut from 0.27 mm thick sheets. Normal magnetization curve and energy loss have been determined by means of a digitally controlled single strip tester from 1 Hz to 1 kHz at peak magnetic polarization values Jp = 1000 mT and 1700 mT. The results fit into a simple phenomenological model regarding the dependence of magnetization curve and energy loss on the strip width, in substantial continuity with the approach originally developed for non-oriented electrical steels. The hysteresis Wh and excess Wexc loss components are shown to depend on the strip width according to a hyperbolic law, with a limiting fully hardened strip predicted to occur for widths around 3.5 mm. It is then consistently observed that the mechanical cutting of standard 30 mm wide HGO Epstein strips is conducive to an increase of the energy loss at 50 Hz and 1.7 T of the order of 13 %

Self-Organizing Equilibrium Patterns of Multiple Permanent Magnets Floating Freely under the Action of a Central Attractive Magnetic Force

The present communication revisits the almost century-and-a-half-old problem of some identical small magnets floating freely on the water’s surface under the action of a superimposing magnetic field created by a stronger magnet placed above them. Originally introduced and performed by Alfred Marshall Mayer and reported in a series of articles starting from 1878 onward, the proposed experiments were intended to provide a model (theoretical and educational) for the building block of matter that, at a microscopic level, is the atom. The self-organizing patterns formed by the repelling small magnets under the influence of a single attractive central force are presented in a slightly different reenactment of the original experiments. Although the set-up is characterized by an axially symmetric magnetostatic structure, and the floated magnets are all identical, the resulting equilibrium patterns are not necessarily symmetrical, as one would expect. To the authors’ best knowledge, the present communication proposes for the first time a quantitative approach to that extremely complex conceptual problem by providing a methodology for computing the equilibrium point coordinates in the case of n = 1…20 floating magnets, as proposed by the original A.M. Mayer experiments. A good agreement between the experiments and computed data was demonstrated for n = 2…15 (1st variant), but it was less accurate while still preserving the experimental set-up configurations for n = 15 (2nd variant)…20. Finally, this study draws the conclusions from the performed experiments and their corresponding computer simulations, identifies some open issues, and outlines possible solutions to address them, as well as future developments concerning the subject in general

Additive Manufactured Magnesium-Based Scaffolds for Tissue Engineering

Additive manufacturing (AM) is an important technology that led to a high evolution in the manufacture of personalized implants adapted to the anatomical requirements of patients. Due to a worldwide graft shortage, synthetic scaffolds must be developed. Regarding this aspect, biodegradable materials such as magnesium and its alloys are a possible solution because the second surgery for implant removal is eliminated. Magnesium (Mg) exhibits mechanical properties, which are similar to human bone, biodegradability in human fluids, high biocompatibility, and increased ability to stimulate new bone formation. A current research trend consists of Mg-based scaffold design and manufacture using AM technologies. This review presents the importance of biodegradable implants in treating bone defects, the most used AM methods to produce Mg scaffolds based on powder metallurgy, AM-manufactured implants properties, and in vitro and in vivo analysis. Scaffold properties such as biodegradation, densification, mechanical properties, microstructure, and biocompatibility are presented with examples extracted from the recent literature. The challenges for AM-produced Mg implants by taking into account the available literature are also discussed