Grenoble Electrical Engineering Lab (G2Elab); CNRS / UGA
New Investigations in Loss Surface model: Towards a universal, precise and robust scalar hysteresis model
The LS model is a scalar hysteresis model including all dynamic effects. The presentation will describe the significant improvements achieved in recent years. The new model is extended to high B and dB/dt based on analytical formulas requiring very few identification data. Its generality, robustness and accuracy are confirmed by extensive experimental validation and analysis on many types of materials and under various severe excitation conditions. The presentation will also address characterization issues and describe the measurement bench used for the identification and verification of the LS model.
Ferromagnetic Damping and Spin-Transport Across Interfaces in Thin-Film Spintronic Systems
Ferromagnetic damping is fundamental to the dynamics of all magnetisation processes and can be critical in magnetic material choices for applications. Until recently, such fundamental behaviour was determined directly by the intrinsic nature of the magnetic materials. However, with thin-film production methods novel “synthetic materials” can now be developed by combining ultrathin-film layers of magnetic and non-magnetic materials to control and enhanced functional performance beyond that of the basic ferromagnetic material. In the case of ferromagnetic resonance behaviour, the magnetic damping can be artificially enhanced by controlled layering of ferromagnetic thin-films with non-magnetic metals. This effect on damping and other interfacial effects can be significant for applications. These interfacial effects are introduced and their potential in applications, such a RF absorption, will be described.
Carlo Stefano Ragusa
Politecnico di Torino
High-frequency losses of soft magnetic materials: measurements and modeling approaches
Present-day soft magnetic materials are required to cover a broadening range of applications, under the increasing demand for efficient cores upon a wide range of operating frequencies and their fitting to the evolving needs imposed by the diversification of the electrical energy sources and the evolution of the related distribution technologies. The widespread use of power converters and their development based on fast semiconductors, such as SiC and GaN, requires, for example, soft magnetic cores with low losses at high frequencies. A case in point is that of soft ferrites and amorphous/nanocrystalline alloys, which can display high permeability values from quasi-static excitation up to the MHz range. But, also the conventional GO and NO steels sheets are required to improve their high-frequency performances, to meet the pressure of novel applications, like transformer cores operating in the kHz range and at high flux densities and the high-speed rotating machines. This presentation will discuss the measuring methods developed for the characterization of different soft magnetic materials over a broad range of frequencies. In soft ferrites and nanocrystalline cores, the range DC- 1 GHz will be covered, and the challenges posed to the theoretical assessment of the magnetic losses will be discussed. The loss behavior of GO laminations and bulk powder cores up to 10 kHz, where the theory again is challenged by the rise of the skin effect in the sheets and by the heterogeneous character of the bonded cores, will also be considered. The modeling approaches developed in recent times regarding the phenomenology of losses in all these cases will be synthetically discussed, highlighting the role of loss decomposition and its generalization to a variety of materials and exciting conditions.
Fernando J.G. Landgraf
Universidade de São Paulo
Grain Size and Losses: Estimating Average Grain Size, and Impact on Hysteresis Loss Slope x Inverse Grain Size
As e-mobility traction motors press for higher frequency excitation, thinner sheets are being proposed to lower total magnetic losses of electrical steels. The presentation will address how thickness affects the effect of grain size on hysteresis loss of silicon steels at maximum induction of 1.0 tesla.
Measurement methods for characterisation of magnetic properties of stator cores
In the design process of electric motors and generators the power losses of stator cores are calculated based on the material supplier’s data from standard magnetic measurements performed under sinusoidal magnetization and with no-external stress exerted on the tested samples. This type of data is insufficient for accurate prediction of machine performance as it does not include the additional loss in the real motor operating conditions from the non-sinusoidal excitation nor the detrimental influence of mechanical and thermal stresses during production of the motor components, such as stator and rotor cores. Furthermore, in the manufacturing of electrical machines a considerable attention is given to the measurements of mechanical dimensions of magnetic cores, whereas verification of their magnetic properties is typically neglected. This in return, leads to inconsistent efficiency of assembled machines as the differences between the actual and initial magnetic properties of the materials and components are significant. In this presentation the experimental data obtained with Brockhaus measurement systems which emphasized the requirement for advanced characterization of stator cores at various design and production stages will be discussed.
3D Magnetic Field Measurements and Advanced Analysis of Permanent Magnets with a Magnetic Field Camera Solution
Magcam presents state-of-the-art high resolution 3D magnetic field mapping on permanent magnets of the (Bx, By, Bz) magnetic field vector components in 3D space, resulting in measurement data with 6 degrees of freedom. These measurements are performed using a high speed 3D magnetic field camera, featuring an integrated 2D Hall sensor array, mounted on a 3-axis mechanical scan stage. Volume 3D magnetic field distribution measurements of sensor magnets can be analyzed using a powerful and versatile data analysis software, which allows virtually unlimited possibilities for the data analysis and quality control of permanent magnets. Measuring the spatial distribution of the full vector magnetic field (Bx,By,Bz) opens a new dimension of possibilities in the inspection of permanent magnets. From the Cartesian components, a range of derived magnetic field quantities are readily derived, such as B (full field), Bxy (field in the XY plane), the azimuth angle (angle of the field vector in the XY plane) and polar angle (angle of the field vector out of the XY plane). These derived quantities are often exactly the important magnet characteristics that determine the performance of the magnet in the end application. With Magcam’s MagScope software, we can analyze a number of important characteristics of permanent magnets: Fast and accurate quality inspection of permanent magnets is increasingly important in development, production and quality control of ever more accurate and reliable sensors as widely used in automotive applications, more efficient electric drives for e.g. electric vehicles, new medical devices, consumer electronics and many other magnet applications. Furthermore, in many high-end applications a 100% magnet quality control is desired, but not feasible with classical magnetic measurement equipment. Also in sensor R&D there is a need for fast and advanced magnet characterization tools for developing next-generation magnetic sensor concepts and assemblies.
Advanced Steel Research Centre, Warwick University
Electromagnetic Sensors for In-Situ Monitoring of Steel Microstructure During Annealing and Tempering
Interstitial-free (IF) steels are widely used in the automotive industry due to their excellent formability. During IF steel processing, knowing when the recrystallisation occurs and is completed would significantly benefit the continuous annealing lines to run efficiently. In this study, a high-temperature cylindrical EM sensor capable of operating at high temperatures inside a furnace has been developed. In-situ EM sensor measurements during annealing heat treatments at a range of temperatures from 365 – 700°C for IF steel grade is reported. The predicted relative permeability values have been correlated with microstructural parameter changes.
Extended Capability for the Characterisation of Soft Magnetic Materials in Response to Industry Requirements
Traditionally National Measurement Institutes (NMI’s) have maintained and disseminated a range of measurement standards, with traceability to SI units, with most common magnetic parameters generally measured in accordance with the IEC 60404 series of standards. These standards outline methodologies and good practice but can be limited, in that they generally don’t cover operational conditions encountered in many industrial applications. Increasingly, NMI’s such as NPL, are being asked to provide materials characterisation beyond the limits of existing standards, but crucially, are underpinned by a robust methodology, have traceability to national standards and detailed uncertainty evaluation to improve the quality of the results. This presentation will outline the current research and development of NPL’s capabilities to characterise soft magnetic materials at higher frequencies, elevated temperature, under stress and at the materials ‘end-of-life’.
State Key Laboratory of EERI
Vector hysteresis modeling and core loss calculation of the magnetic materials
Considering that the procession trajectory of the magnetic moment under the excitation of the external field presents a strong nonlinear characteristic, the catastrophe theory is introduced to model the magnetization process of materials in this paper. Firstly, the free energy equation is obtained according to the physical properties of the material. And it is transformed into the potential function equation and the catastrophe manifold of the potential function is obtained by using the catastrophe theory. Then the hysteresis operator is determined by the branch curve and force field line, which are found in the abrupt manifold. At last, the interaction between operators and the distribution function of operators are introduced to determine the global vector model. It is proved that this modeling method has clear physical significance and practicability by the analysis of the abrupt change of the system under different free energy and the experimental verification of vector model. Under the condition that the permeability and dielectric coefficient are second-order tensors, a formula for calculating the loss caused by the anisotropy of materials is derived from the formula of the flow density of electromagnetic energy. The Poynting vector formula for the core loss calculation is divided into five parts:1. the electromagnetic energy flow, 2. the eddy-current loss, 3. the effect of material anisotropy on eddy current loss, 4. the effect of magnetic anisotropy for electromagnetic energy flow, 5. the magnetic anisotropic loss. As a result, the precision of the core loss calculation will be improved.
Cardiff University, MAGMA Centre
Measurement methods for characterisation of magnetic properties of stator cores
The importance of being able to characterise soft magnetic materials under different magnetisation conditions is becoming increasingly important. Applications that require electrical steels are experiencing a much more complex set of conditions than before, from distortions caused from PWM inverters, filters and even enviromental factors such as geomagnetically induced quasi-DC currents. This talk discusses ways to repeatabily measure the key characteristics of these materials.
Paragraf Ltd, Oxford Instruments
Graphene-based Hall Effect Magnetic Field Sensors
Graphene-based Hall Effect sensors hold the promise of revolutionising magnetic field measurement, by combining extremely high sensitivity with the simplicity and versatility of Hall sensor operation. The unique properties of graphene also make measurements possible at ultra-low temperatures, allowing in-situ field measurements in experimental environments which were previously inaccessible. Measurements in a wide magnetic field range are possible, with high measurement resolution and low noise performance. In this poster, we show results of tests on graphene Hall sensors made by Paragraf, at a wide range of temperatures, and in magnetic fields up to 8 T. A magnetic field resolution better than 5 micro-T is achievable. The sensors were operated at currents as low as 1 micro-A, implying a heat dissipation of just 50 nW, enabling operation in ultra-low temperature environments.