Magnetic measurements, carried out by means of the Epstein frame, have shown that most typical dynamo steel sheets have certain anisotropic properties. In numerical analysis, anisotropic properties are taken into account with the use of the special function of the grain distribution in the given dynamo sheet. For engineering purposes, it is desirable to assess the influence of these properties on the changes of the magnetic flux density in typical dynamo steel sheets, especially during the rotational magnetization. For this purpose, measurements of the flux density changes and field strength changes in the circular-shaped samples of two selected typical dynamo sheets were performed. These measurements were carried out for several values of the current flowing in windings which generated the axial or rotational magnetic field in the test dynamo sheet. The influence of the magnetic anisotropy on the magnetization process was briefly discussed for both types of the magnetization processes.
In this study, BaFe12-2xCoxTixO19 (X : 0 to 2.0, 0.2) powders were synthesized by sol-gel process. TG-DTA, XRD, SEM, VSM, and Network analyzer were measured in order to influence easy magnetization axis change on the wave absorption frequency range change. The easy magnetization axis change of the annealed powder at 900°C and 1200°C was confirmed by the coercive force decreased 4,800 and 3,870 Oe to 260 and 269 Oe, respectively, at the substitution ratio of 0.8 and 1.0. And it was confirmed that the change of the easy magnetization axis affected the change of the wave absorption frequency. The wave absorption frequency of substituted Barium Ferrite was less than 10 GHz range after the easy magnetization axis of Barium ferrite changed to a-b plan direction. It was confirmed the BaFe12-2xCoxTixO19(x = 0.8 to 1.6) was synthesized by the sol-gel process and it was annealed at 900°C and 1200°C, which could be used as a wave absorber in the X-band region of 10 GHz less.
Group of steel balls with different chemical composition, diameters and nitriding treatment parameters were investigated with using magnetic resonance and magnetization methods. Emerging nitrided regions consists of diffusion and surface layer of iron nitrides. The thickness of the individual layers depends on the type of steel and process parameters. Resonance signal shape and position were successfully described in the ferromagnetic resonance regime expected for dense iron magnetic system. Influence of the sample size, thermal treatment and carbon content on the absorption signal has been analyzed. Significant magnetic anisotropy has been revealed, as well as non-usual increasing of the magnetization as a function of temperature. It suggests, that overall antiferromagnetic ordering, destroyed by thermal movement, lead to increasing of the ferromagnetic region.
Accurate demagnetization modelling is mandatory for a reliable design of rare-earth permanent magnet applications, such as e.g. synchronous machines. The magnetization of rare-earth permanent magnets requires high magnetizing fields. For technical reasons, it is not always possible to completely and homogeneously achieve the required field strength during a pulse magnetization, due to stray fields or eddy currents. Not sufficiently magnetized magnets lose remanence as well as coercivity and the demagnetization characteristic becomes strongly nonlinear. It is state of the art to treat demagnetization curves as linear. This paper presents an approach to model the nonlinear demagnetization in dependence on the magnetization field strength. Measurements of magnetization dependent demagnetization characteristics of rare-earth permanent magnets are compared to an analytical model description. The physical meaning of the model parameters and the influence on them by incomplete magnetization are discussed for different rare-earth permanent magnet materials. Basically, the analytic function is able to map the occurring magnetization dependent demagnetization behavior. However, if the magnetization is incomplete, the model parameters have a strong nonlinear behavior and can only be partially attributed to physical effects. As a benefit the model can represent nonlinear demagnetization using a few parameters only. The original analytical model is from literature but has been adapted for the incomplete magnetization. The discussed effect is not sufficiently accurate modelled in literature. The sparse data in literature has been supplemented with additional pulsed-field magnetometer measurements.
In this paper, the properties of AE signals originating from phenomena occurring during magnetization of ferromagnetic materials which are used to construct power transformer cores are presented. The AE signals in a selected power oil transformer were recorded and analyzed. The analysis included, i.e., time, frequency, and time-frequency analyses, calculations of amplitude distributions of the signals and defined AE descriptors, determination of the descriptor map on the side walls of transformers, as well as a detailed analysis of selected part of the signals.
The maps of descriptors were analyzed in the frequency bands of 20–70 kHz, 70–100 kHz, and 100–200 kHz. The analysis of the properties of the signals was performed in time and frequency domains. Based on the analysis, there were identified the AE signals originating from the phenomena occurring during the core magnetization of a power oil transformer. To identify those phenomena, the maps of the ADC descriptor calculated in the band of 20–70 kHz when selecting the measurement points in which there were no AE sources from partial discharges were used.
An analysis of magnetoacoustic emission signals in the bands of 70–100 kHz and 100–200 kHz was also performed. The analysis of the signal properties in such an extended frequency range allowed determining the properties of the magnetoacoustic signals coming from core sheets of power oil transformers.
The Goss texture is a characteristic feature of grain-oriented transformer steel sheets. Generator sheets, which are produced as non-oriented steel sheets, should have isotropic features. However, measurement results of generator sheets, confirmed by crystallographic studies, indicate that these sheets are characterized by certain, quite significant anisotropy. The first purpose of this paper is to present the influence of textures of generator and transformer steel sheets on their magnetization characteristics. The second aim is to propose a method which takes into account the sheet textures in the calculations of magnetization curves. In calculations of magnetization processes in electrical steel sheets, models in which the plane of a sheet sample is divided into an assumed number of specified directions are used. To each direction a certain hysteresis loop, the so-called direction hysteresis, is assigned. The parameters of these direction hystereses depend, among other things, on the texture type in these steel sheets. This paper discusses the method which calculates the parameters of these direction hystereses taking into account the given sheet texture. The proposed method gives a possibility of determining the magnetization characteristics for any direction of the field intensity changes.
The paper presents a construction of magnetic observatory "Arctowski" on King George Island. The parameters of magnetic instruments and mean values of D, H, Z and F(T) of magnetic field are presented. Examples of registration of changes of the magnetic field are noted.
The accurate prediction of iron losses has become a prominent problem in electromagnetic machine design. The basis of all iron loss models is found in the spatial field-locus of the magnetic flux density (B) and magnetic field (H). In this paper the behavior of the measured BH-field-loci is considered in FEM simulation. For this purpose, a vector hysteresis model is parameterized based on the global measurements, which then can be used to reproduce the measurement system and obtain more detailed insights on the device and its local field distribution. The IEM has designed a rotary loss tester for electrical steel, which can apply arbitrary BH-field-loci occurring during electrical machine operation. Despite its simplicity, the proposed pragmatic analytical model for vector hysteresis provides very promising results.
The article presents the results of tests of the application of magnetic fuel activators, which improve the efficiency of metallurgical furnaces and positively affect the ecological aspects of their work. Energy indicators for metallurgical furnaces during operation before and after installation of magnetic fuel activators as well as the results of composition and concentration of emitted pollutants are included in the paper. The magnetic activation of liquid and gaseous fuels modifies their structure. As a result of the activation, the fuel mixture is selectively saturated with oxygen in the zone of free fuel flow. The combustion conditions were close to optimal, which is confirmed by the reduction of pollutants in the exhaust gases. Fuel saving in the combustion process is also a measurable economic effect. The tests included ovens of several types: pusher furnace, one and two chamber furnaces and a furnace with a rotary shaft. Several-month measurement cycles were carried out on each of them. The experiments consisted in the analysis of gas and heat consumption per month in individual furnaces before and after the use of magnetic fuel activators. The effectiveness of using activators was determined on the basis of the results of the tests carried out. As a result of a twelve-month test cycle on the pusher type furnace, a 36% reduction in gas consumption and a 22% reduction in heat consumption were achieved. After a seventeen-month measurement cycle on chamber furnaces, a 35% reduction in gas consumption and 6% in heat consumption were achieved. The tests on furnaces with a rotary shaft lasted fourteen months and showed a reduction in gas consumption by 8%. An improvement in the composition of fumes in the furnace atmosphere was achieved in all units with magnetic activators installed, as well as a reduction in the emission of harmful pollutants into the atmosphere from the installation.
This paper describes the method of prospective magnetic research under natural conditions of strong interference by the external variable magnetic field. This method of synchronized measurements, when some given assumptions are satisfied, permits magnetic survey of the accuracy 1-2 nT to be carried out. It was used in detailed investigations of weak anomalous fields.
The results and method of measurements of D, H and T carried out at Hornsund in the summer of 1979 are presented. The relative and absolute values of these elements are given in reduction to the Polish magnetic station at Hornsund. An initial evaluation of changes in the magnetic field from 1957 to 1979 is carried out.
The paper presents the method and results of measurements carried out at four secular points: P, — Wilczekodden, P2 — Hyttevika, P3 — Gashamna and P4 — Treskelodden. No essential changes were found in the distribution of the anomalous field ΔT with respect to the results of observations made in 1979.
This paper presents the results of magnetic mapping carried out in the area of the metamorphic series of Ariekammen and Skoddefjellet. On the basis of qualitative interpretation of measurements a number of anomalous zones were distinguished, whose position can be correlated with local changes in mineralitation and polymetallic ore content in the Fuglebergsletta area. The SE-NW orientation, skew to the almost meridional run of the layers of slates and marbles making up the metamorphic complex, dominates in the course of the anomalous zones.
The work discusses numerical and experimental researches, which are focused on developing a coherent model of magnetic interactions causing the levitation of the starting trolley of the unmanned aerial vehicle (UAV) catapult. The starting trolley is levitating over the catapult’s tracks, which generate the magnetic field. The levitation is made possible by the diamagnetic properties of high-temperature superconductors, placed in supports of the starting trolley. The introduction of the article briefly analyzes the catapult structure. Next, it explains the nature of associated with the Meissner and flux pinning effect magnetic interactions which causes the levitation phenomenon. The paper presents the results of numerical analysis of the magnetic field, generated by the catapult’s tracks arranged in two configurations: a “chessboard” and a “gutter” pattern. The numerical model was solved, using the finite element method. Parameterization of the numerical model was made based on the measurements of the magnetic field, generated by a single magnet.
This paper presents a review of the electromagnetic field and a performance analysis of a radial flux interior permanent magnet (IPM) machine designed to achieve 80 kW and 125 Nmfor an electric and hybrid traction vehicle. The motor consists of a 12-slot stator with a three-phase concentrated winding as well as an 8-pole rotor with V-shaped magnets. Selected motor parameters obtained from an IPM prototype were compared with the design requirements. Based on the electromagnetic field analysis, the authors have indicated the parts of the motor that should be redesigned, including the structure of the rotor core, aimed at enhancing the motor’s performance and adjusting segmentation for magnet eddy current loss reduction. In addition, iron and PM eddy current losses were investigated. Moreover, transient analysis of current peak value showed that the current may increase significantly compared to steady-state values.Amap of transient peak current load vs. torque load plotted against rotor speed was provided. Based on the numeric and analytical results of physical machine parameters, the authors indicate that collapse load during the motor’s operation may significantly increase the risk of permanent magnet (PM) demagnetization. It was also found that collapse load increases the transient torque, which may reduce the lifetime of windings.