LABORATORY STUDIES OF PROPERTIES OF SOFT MAGNETIC POWDER COMPOSITE MATERIALS

Изучение эффективности использования электротехнических материалов является актуальной проблемой в области изготовления электрических машин. Одним из важнейших аспектов изготовления электрических машин является проектирование магнитной системы машины. В качестве магнитной системы используют магнитопроводы из различных магнитомягких материалов. Эти материалы отличаются магнитной проницаемостью и удельными магнитными потерями. Данные параметры материалов влияют на нагрев, размер, стоимость и эффективность электрической машины. В целях экономии экспериментальная оценка параметров магнитомягких материалов производится на заготовках различных форм и размеров, на специальных измерительных стендах, согласно международным энергетическим стандартам. В данной статье предлагается экспериментальная установка для лабораторных исследований магнитных свойств магнитомягких материалов, методом кольцевых заготовок, в соответствие со стандартом МЭК-60404-6. В составе установки используется только стандартное недорогое оборудование. Необходимый коэффициент формы магнитной индукциидостигается последовательной коррекциейнапряжения вторичной обмотки с помощью цифрового регулятора. Подход к программной реализации алгоритма последовательной коррекции напряжения вторичной обмотки изложен в статье. С помощью предлагаемой установки проведено исследование свойств образца из магнитомягкого композиционного порошкового материала Somaloy 700-3p (800 MPa) и сравнение результатов с каталожными данными производителя. По итогам работы выявлено, что с помощью предлагаемойустановки могут производитьсяизмерения свойств магнитомягких материалов, в соответствие со стандартом МЭК-60404-6 с необходимой точностью. Предлагаемая установка может быть использована как в качестве учебного стенда, так и в качестве измерительной установки для идентификации свойств магнитомягких материалов при проектировании электрических машин. The study of the efficiency of using electrical materials is of great interest in the field of manufacturing electrical machines. One of the most important aspects of the manufacture of electrical machines is the design of the magnetic cores of the machine. Magnetic cores made of various magnetically soft materials are used as a magnetic system. These materials differ in magnetic permeability and specific magnetic losses. These material parameters affect the heating, size, cost and efficiency of electric machines. In order to reduce expenses, the experimental evaluation of the parameters of soft magnetic materials is carried out on samples of various shapes and sizes, on special experimental setups, in accordance with international electrotechnical standards. This article proposes an experimental setup for laboratory studies of the magnetic properties of soft magnetic materials by the method of ring specimens, in accordance with the IEC-60404-6 standard. The setup uses only standard inexpensive equipment. The required shape factor of the magnetic flux density is achieved by sequential correction of the secondary winding voltage using a digital regulator. The approach to the software implementation of the algorithm for sequential correction of the secondary winding voltage is described in the article. The proposed experimental setup was used to study the properties of a sample made of a soft magnetic composite powder material Somaloy 700-3p (800 MPa) and compare the results with the manufacturer's catalog data. Based on the results of the work, it was revealed that the proposed setup can be used to measure the properties of soft magnetic materials in accordance with the IEC-60404-6 standard with the required accuracy. The proposed experimental setup can be used both as a training stand and as a measuring installation for identifying the properties of soft magnetic materials in the design of electrical machines.

The development of microfabricated solenoids with magnetic cores for micromagnetic neural stimulation

Electrical stimulation via invasive microelectrodes is commonly used to treat a wide range of neurological and psychiatric conditions. Despite its remarkable success, the stimulation performance is not sustainable since the electrodes become encapsulated by gliosis due to foreign body reactions. Magnetic stimulation overcomes these limitations by eliminating the need for a metal-electrode contact. Here, we demonstrate a novel microfabricated solenoid inductor (80 µm × 40 µm) with a magnetic core that can activate neuronal tissue. The characterization and proof-of-concept of the device raise the possibility that micromagnetic stimulation solenoids that are small enough to be implanted within the brain may prove to be an effective alternative to existing electrode-based stimulation devices for chronic neural interfacing applications.

Topology optimization of magnetic cores for WPT using the geometry projection method

Purpose The purpose of this study is to search for an optimal core shape that is robust against misalignment between the transmitting and receiving coils of the wireless power transfer (WPT) device. During the optimization process, the authors maximize the coupling coefficients while minimizing the leakage flux around the coils to ensure the safety of the WPT device. Design/methodology/approach In this study, a novel topology optimization method for WPT devices using the geometry projection method is proposed to optimize the magnetic core shape. This method facilitates the generation of bar-shaped magnetic cores because the material distribution is represented by a set of elementary bars. Findings It is shown that an optimized core shape, which is obtained through topology optimization, effectively increases the net magnetic flux interlinked with the receiving coil and outperforms the conventional core. Originality/value In the previous topology optimization method, the material distribution is represented by a linear combination of Gaussian functions. However, this method does not usually result in bar-shaped cores, which are widely used in WPT. In this study, the authors propose a novel topology optimization method for WPT devices using geometry projection that is used in structural optimization, such as beam and cantilever shapes.

Method for determining of the optimal thickness of sheets of magnetic cores of electrical machines by the wattmeter method

The problem of reducing magnetic losses (no-load losses) in the steel of the magnetic cores of electrical machines is investigated. The tasc of determining the optimal thickness of steel sheets of the magnetic circuit of an electric machine is considered. The criterion for optimality is the minimum power of magnetic losses in steel. Currently, this problem does not have an exact solution due to the fact that the exact ratio of the hysteresis and eddy current components of magnetic losses in steel is unknown. Analyzed the power of magnetic losses in modern electrical machines and devices, depending on the thickness of the sheets of electrical steel. A method is proposed for determining the optimal thickness of steel sheets of the magnetic circuit of an electric machine based on the wattmeter method. In the course of the experiment, two identical magnetic circuits were selected from steel sheets of different thicknesses, for which the losses in steel were measured at different frequencies of magnetization reversal and the optimal thickness of the sheets was calculated. The proposed formula for calculating the thickness of the sheets is valid for both isotropic and anisotropic steel. The proposed technique can be used for both transformers and electric motors and generators.

A Hybrid Common Mode Choke Optimization Method for Input Line EMI Filter Design

In this paper, an optimization method of toroidal core-based Hybrid common-mode chokes (HCMCs) for the design of an Electromagnetic interferences (EMI) filter is proposed. A dedicated algorithm is developed using MATLAB to characterize compact HCMCs that exhibit effective CommonMode (CM) chokes with optimized leakage inductances by systematic variations in the winding patterns and geometric dimensions of their magnetic cores. It takes into consideration the physical limitations of these components as well as the constraints related to the design of EMI filters. The proposed algorithm allows through a small computational task to propose a variety of configurations for optimal HCMCs. Finite element method (FEM) simulations are conducted on the HCMCs to extract their CM and leakage inductances. The results are compared with those calculated analytically and yield a good match. The performances of optimized HCMCs are evaluated through their implementation in the designed filter. All the cases of HCMCs including the smallest one allow the EMI filter to easily qualify a power converter to an electromagnetic compatibility (EMC) standard.

Formation of Orthogonal Components of Input Currents in Microprocessor Protections of Electrical Equipment

The methods used in the microprocessor protection of electrical equipment for forming orthogonal components of input currents ensure their reliable isolation after changing the mode followed by one or more periods of the fundamental frequency. This is due to the inertia of the functional elements, in particular, digital frequency filters, as well as the saturation of the steel magnetic cores of current transformers. To increase the speed of the selection of orthogonal components of the input currents, it is proposed to form them as equivalent ones in terms of the cosine and sine components obtained using digital Fourier filters by multiplying by the resulting coefficient. The method that has been developed for determining the specified coefficient provides compensation for the delay caused by the inertia of digital filters, as well as the saturation of the steel of magnetic cores of current transformers. The proposed method of forming orthogonal components is highly effective in the modes of strong saturation of the magnetic core with a complex input action in the presence of an aperiodic component with a large damping time constant. The evaluation of the efficiency of the proposed method was performed using a complex digital model implemented in the dynamic modeling environment MatLab-Simulink. As a result of the performed studies, it was found that in the absence of saturation of the magnetic core of current transformers, as well as in the presence of a small and medium degree of saturation, the proposed method for forming equivalent orthogonal components of input currents has dynamic properties close to the ones of those that had been previously proposed. With a strong saturation of the magnetic core of current transformers, the speed of obtaining reliable values of these components is increased by 1.5–2 times.