Showing papers on "Magnetic core published in 2022"

A Compact EMI Filter Design by Reducing the Common-Mode Inductance With Chaotic PWM Technique

Abstract: Passive electromagnetic interference filters (PEFs) are the most common way to solve electromagnetic interference (EMI) problems in power converters. However, PEFs bring additional volume, weight, and cost for power converters, especially common-mode (CM) inductors in PEFs, and it is a tricky issue for the high-power-density converters that must meet the electromagnetic compatibility specification. In order to design compact PEFs for power converters with pulsewidth modulation (PWM), a volume reduction method of CM inductors with chaotic PWM (CPWM) is proposed in this article. First, the mechanism that CPWM reduces the CM inductance by increasing the corner frequency is analyzed. Second, the relationship between the reduction of EMI spectrum magnitude by CPWM and the decrease of the CM inductance is quantitatively calculated. Third, utilization rate of the magnetic core η is defined to reasonably compare the size of the different inductors under traditional PWM and CPWM. Finally, the proposed design method of CM EMI filters is applied into a dc–dc converter and a dc–ac inverter, respectively, to verify its effectiveness and feasibility. In a dc–dc converter with the switching frequency 100 kHz, 275 W, the volume of the CM inductor and the volume of CM EMI filters are reduced by 63.5% and 48.3%, respectively, by using the proposed compact EMI filter.

A Soft-Switching Interleaved Buck–Boost LED Driver With Coupled Inductor

Abstract: In this article, a novel dc–dc light-emitting diode driver employing an interleaved converter is proposed and analyzed. The circuit topology mainly consists of two parallel buck–boost converters. A coupled inductor, which is composed of a magnetic core and two windings, is used to replace the energy storage inductors of the two buck–boost converters. This not only does not add any components, but also saves a magnetic core. The buck–boost converters are designed to operate near boundary conduction mode. Due to the characteristics of magnetic flux balance, the magnetic-excited current can be converted between the windings of the coupled inductor. By using the magnetic-excited current to release the charge stored in the parasitic capacitors of the active switches, these switches can fulfill zero-voltage switching on (ZVS) without the use of any auxiliary switches, active clamping circuits, or snubber circuits. Moreover, the freewheel diodes of both buck–boost converters can achieve zero-current switching off (ZCS). The steady-state analyses for different operation modes are provided, and the mathematical equations for designing circuit components are conducted. Finally, a 200-W prototype circuit was built and tested to verify the analytical predictions. According to the experimental results, all the semiconductor devices are operated at either ZVS or ZCS, and the circuit efficiency as high as 95.0% is measured. Satisfactory performance has verified the feasibility of the proposed converter.

A Hybrid Analytical Model for Permanent Magnet Vernier Machines Considering Saturation Effect

Abstract: This article proposes a new hybrid analytical model combining subdomain model and equivalent magnetic network for permanent magnet vernier machines, which are easy to get saturated due to the air-gap field modulation effect. The key is representing saturation effect by iterating equivalent surface current as part of interface conditions in the proposed subdomain model. First, five subdomains are divided to calculate magnetic field distribution. The equivalent surface current is utilized as the boundary constraint between subdomains and iron core. Second, the equivalent magnetic network is established based on stator structure, and the fluxes flowing into flux modulation poles are equivalent as the magnetic flux sources. Node magnetic potentials can be achieved with the application of Kirchhoff's law of current. Then, the equivalent surface current is updated for convergence by node magnetic potential to accurately predict saturated performance. Finally, a prototype is manufactured, and the effectiveness of the proposed hybrid model is verified by the finite-element analysis (FEA) and experimental results. The hybrid model combines the subdomain model and the equivalent magnetic network model to complement each other and it is demonstrated to be more efficient than the FEA model while maintaining high accuracy.

High Voltage Pulse Generator Based on a Novel Magnetic Isolated Drive Circuit

Abstract: In order to meet the requirements of high voltage, high power, and compactness for pulse generators used in the field of liquid food sterilization, an all-solid-state Marx generator based on a novel magnetic isolated drive is proposed. The drive circuit uses the magnetic core to transfer the control signal, which adopts core stacking and inverse paralleled secondary side winding. It only needs one drive signal to realize synchronous conduction of the main switch or bypass switch and the complementary conduction of both. The maximum pulse width of drive signal is not limited by the magnetic core saturation. The topology is simple, and the problem of high voltage isolated drive of Marx generator is solved. Based on the novel magnetic drive, a 31-module solid-state Marx generator is built and a prototype test is carried out. The test results show that the maximum instantaneous power of this generator is 1.3 MW (30 kV, 43 A) with a pulse width of 3–10 μs and an adjustable repetition frequency of 0–1 kHz.

Performances comparison of axial-flux permanent-magnet generators for small-scale vertical-axis wind turbine

Abstract: The use of wind energy as an alternative source of energy to generate the electricity is increasing worldwide. The application of an axial flux permanent magnet generator for small-scale wind turbine nowadays is increasing due to innovation, new material discoveries and completion in the manufacturing technology. The axial flux machines can be constructed with single-side, double-side and multi-stage topologies and can also be constructed with or without an iron core. Nine possible patterns between the single-side and double-side topologies with iron core and with surface-mounted permanent magnet method were designed in this study with the aid of the analytical method. To obtain the most qualified generator, there are six parameters used as constraints including flux density distribution, on-load terminal voltage, voltage regulation, total harmonic distortion, output power, and efficiency and analyzed with the finite element method from Maxwell-3D software. From the comparison, the generator type IX excited with rectangular poles is proven to be the most qualified generator among other generators in this case.

Parasitic Capacitance Modeling of Inductors Without Using the Floating Voltage Potential of Core

Abstract: The analytical modeling of parasitic capacitances in inductors is commonly based on the energy-conservation law. Yet, in order to calculate the equivalent capacitances of inductors, the floating voltage potential of magnetic core is required to be preknown in all previous modeling methods. This letter proposes an analytical method for calculating the parasitic capacitances of the inductors with low-resistivity cores, which does not require any prior knowledge of the floating core potential. The proposed modeling method can be extended to the transformers as well as multiterminal magnetic devices. The experimental results verify the effectiveness of the proposed method.

Designing an M-Shape Magnetic Coupler for the Wireless Charging System in Railway Applications

Abstract: The wireless power supply solution has shown great advantages in rail transit applications, such as maglev trains and trams. However, research works on designing the magnetic coupler for wireless charging system in rail applications, which is a crucial problem, are not sufficient. Considering the high power and lightweight requirements, this article selects the coaxial M-shape magnetic coupler with LCL /S compensation for railway applications, which contains the transmitting rail and the receiving coil wound on an M-shape magnetic core. First, analysis was conducted on the requirements for inductance parameters of the magnetic coupler under the circuit constraints, including transmission power, input and output voltages, and component electrical stress, etc. Then, the influence of the geometric parameters of the coil structure and misalignment on its inductance parameters is analyzed. Based on these analysis results, the design method for the M-type magnetic coupler based on the lightweight principal is proposed. The geometric parameters are designed following a certain sequence to minimize the number of iterations and FEM simulation parameter sweeps, making the design procedure suitable for engineering practice. According to the proposed method, the magnetic coupler for a 360 kW wireless charging tram is designed and implemented. Through simulations and experiments, the magnetic coupler is verified to be feasible for the system with light weight.

Influence of Magnetic State Variation on Transformer Core Vibration Characteristics and Its Measurement

Abstract: The variation of magnetic state of transformer often causes the violent vibration of the transformer various parts, especially the core. The most obvious magnetic state change of the transformer is usually caused by the dc component. In this article, one kind of magnetic compensation method is adopted to suppress the dc bias, and the core vibration caused by the transformer magnetic state change is studied in detail. At first, on the basis of measuring the magnetostriction and calculating the vibration displacement of transformer core, the research on the vibration increment created by the dc bias is carried out. Second, the transformer core vibration before and after the dc bias suppression is simulated, and the difference of the transformer with a magnetic compensation capacity is analyzed. Finally, based on the VIBXPERT1II FFT data acquisition and signal analyzer, the vibration of measuring points under the different magnetic state and the different measuring point under the same magnetic state are collected. The vibration tendency of each measuring point is given with the variation of the magnetic state. Thus, the vulnerable spot of the core vibration and the basic law of the transformer vibration are obtained, which could provide a basic method for the reducing vibration.1Registered Trademark.

Solid Rotor Core vs. Lamination Rotor Core in Fractional-Slot PMSM Motor with High Power Density

Abstract: Fractional-slot PMSM motors allow for obtaining high values of power density factors, but at the same time, they are characterized by high values of rotor losses—in the rotor core and permanent magnets. The main causes of rotor losses in this type of motor are subharmonics and a high content of higher harmonics in the distribution of the magnetomotive force MMF. The use of a solid rotor core simplifies the construction and technology of the rotor but eddy current losses in the core account for a significant percentage of the total rotor losses. It is well known that a laminated core reduces eddy currents, while for motors with an outer rotor, it complicates the construction and increases weight. Thus, the question arises about the necessity to use a laminated core in a high power density motor and the real benefits of this. The article presents a comparison of the motors with a solid rotor core and a laminated rotor core, considering the value of rotor losses, power density factor, efficiency and the range of rotational speed and range of current load. The analysis was carried out for various types of sheets for laminated core and solid steel and SMC (Soft Magnetic Composite) material for solid rotor core. FEM models were used in the analysis, and the results were partially verified with the results of laboratory tests of motor models. The object of the analysis is a fractional-slot PMSM motor with an external rotor with surface permanent magnets (SPM). Motor weight is about 10 kg, and the maximum power is 50 kW at 4800 rpm.

Analysis of Flux Density and Iron Loss Distributions in Segmented Magnetic Circuits Made With Mixed Electrical Steel Grades

Abstract: This article presents the potential contribution of segmented stator magnetic circuits of rotating permanent magnet electrical machines with concentric winding. Two magnetic materials are mixed: FeSi non-oriented electrical steel and FeSi grain-oriented electrical steel (GOES). The choice of using GOES is based on the high performance it offers in terms of permeability and iron losses compared to conventional non-oriented grain electrical steel (NOES), particularly when GOES is magnetized in the rolling direction (RD). The goal is to analyze the contribution of the mixed magnetic circuit on the losses and electromagnetic torque but also the drawbacks due to the cut process and the assembly. The behavior of the magnetic field at the junction between the segments is studied by comparing different geometrical connection shapes and compared to a reference magnetic circuit fully made with NOES sheets. This comparison is experimentally made with a model representative of the existing phenomena in an electrical machine. In addition, numerical calculations using finite elements software are carried out by considering both the magnetic anisotropy and the saturation of the GOES.

Internal Characterization of Magnetic Cores, Comparison to Finite Element Simulations: A Route for Dimensioning and Condition Monitoring

Abstract: Magnetic cores are typically used in every stage of an electrical energy production and distribution chain. Local defects, including edge burrs and interlaminar faults (ILFs), are detrimental to system performance and should be detected swiftly to ensure high reliability and durability. Real-time magnetic core condition monitoring (MCCM) is a promising solution for rapid fault detection. However, similar to dimensioning or performance evaluation, this monitoring has always been performed through averaged magnetic properties, which limits efficiency. In this domain, significant progress is forecast by achieving precise local measurements. In this study, an innovative solution is proposed to measure local magnetic properties, which is adapted to real-time monitoring and magnetic circuit evaluation. The proposed sensor is a one-piece device that is flat enough to be placed noninvasively between the laminations at distinct positions in the magnetic core. It measures the magnetic excitation and induction fields in two dimensions, which can be used as local inputs for real-time condition monitoring. In this article, the proposed sensor was first detailed, experimental results were provided, and finite-element simulations were performed. The sensor capability was validated both experimentally and through simulation. The results of this study contribute to the development of an intelligent magnetic core that includes an effective real-time monitoring system. The study provides a local validation of the most advanced high-fidelity simulation method, which could be used to predict the responses of magnetic cores and electromagnetic converters to defects of various natures, as well as geometrical and property changes.

Measurement Methods for High-Frequency Characterizations of Permeability, Permittivity, and Core Loss of Mn-Zn Ferrite Cores

Abstract: Manganese–zinc (Mn-Zn) ferrites are the primary choice for high-frequency and high-power magnetic components. Optimum material selection is essential for high-performance magnetic component design. However, the manufacturers’ material specifications usually do not provide sufficient information to optimize the design. Complex permeability and permittivity, as well as specific power loss, are typically provided as one value, regardless of the core shape and size. Magnetic component design based on these incomplete specifications can result in a poorly optimized component. This article proposes methods to determine the properties of Mn-Zn ferrite at high frequencies, with tests up to 20 MHz. This article also presents experimental complex permeability and permittivity frequency characteristics for four ferrite materials: 3E10, 3F36, 3E65, and 3C95. The resulting fitted parameters for the equivalent-circuit model can be used in any design algorithm or simulation tool. The impacts of physical size, temperature and force on complex permeability and permittivity are also considered.

At what frequencies should air-core magnetics be used?

Abstract: Magnetic components for power conversion (inductors & transformers) are often designed with magnetic cores, which add core loss but reduce the required number of turns, copper loss, and usually total loss. At very high frequencies, poor core materials make this tradeoff less advantageous and air-core magnetic components are often preferred. The boundary between the magnetic-core and air-core regimes has not yet been theoretically identified, and intermediate frequency ranges (i.e. 5 to 30 MHz) see both cored and air-core examples. In this work, we calculate an expression that suggests that, based on the properties of currently available magnetic materials, cored inductors can outperform their air-core counterparts up to 60 MHz, well into the VHF range. We experimentally demonstrate this boundary frequency by comparing the quality factors of optimized cored and air-core toroidal inductors. Formally demonstrating the advantage of cored over air-core inductors even at tens of MHz suggests more advantageous designs for applications at ISM bands (6.78, 13.56, 27.12 MHz) and other RF applications.

In-Situ Measurement and Investigation of Winding Loss in High-Frequency Cored Transformers Under Large-Signal Condition

Abstract: This paper presents an in-situ measurement method to accurately characterize the winding loss in high-frequency (HF) transformers, which is challenging to quantify in power electronics applications. This approach adapts the reactive voltage cancellation concept to measure the complete winding loss in HF transformers with the presence of the magnetic core and the load on the secondary side, while this concept was originally brought up for core loss measurement. As an in-situ method, the proposed testing method can factor in the non-linear winding loss elements impacted by the magnetic field interaction between the windings and the core under the large-signal operation, which are not properly assessed in existing approaches. The presented method significantly reduces the sensitivity of the measurement errors linked to the probe phase discrepancy, since the resistive winding loss is well separated out from the core loss. The acquired experimental results are compared and verified with other common empirical measurement methods and three-dimensional (3D) finite element analysis (FEA). As the finding, the measured winding AC resistance is found to be correlated with the load level. Furthermore, treating the complex winding loss and core loss as a black-box problem, this paper proposes a “total loss map” as an engineering solution to practically distribute the measured loss data of magnetic components to the end-users to enable quick and accurate loss estimation/modelling.

Demonstration of Substrate Embedded Ni-Zn Ferrite Core Solenoid Inductors Using a Photosensitive Glass Substrate

Abstract: In this work, we propose a Ni-Zn ferrite core embedding process in a photosensitive glass substrate and demonstrate the design and fabrication of substrate embedded inductors and integrated voltage regulators (IVRs) using the substrate embedded ferrite cores. We developed a ferrite core embedding process inside a vertical cavity of a photosensitive glass substrate, so that ferrite core solenoid inductors can be embedded in the substrate. The measured inductance, DC resistance and Q-factor of a 1600μm × 1500μm ferrite core inductor were 209nH, 240mOhm, 15.8 at 18.2Mhz respectively. And a 920μm × 1050μm inductor has inductance of 252nH, DC resistance of 663mOhm, and Q-factor of 16.6 at 20Mhz. The power conversion efficiency of an integrated voltage regulator module was measured up to 85.2%.

Field-Oriented Control of the Induction Motor as Part of the Shunting Locomotive Powertrain Considering Core Losses and Magnetic Saturation

Abstract: The analysis of the magnetic saturation and core losses effects influence on a field-oriented controlled induction motor current and torque control quality is given. The magnetization circuit active resistance makes it possible to take core losses into account in induction motor electromagnetic processes equations. The rotor flux linkage vector magnitude and rotation angle estimation unit synthesis based on the rotor circuit equations is made considering core losses. The mutual inductance and the core losses circuit resistance estimating technique in a no-load motor mode are presented.

Opportunities in magnetic materials for high-frequency power conversion

Abstract: Power converters are increasingly being operated at switching frequencies beyond 1 MHz to reduce energy storage requirements and passive component size. To achieve this miniaturization, designers of inductors and transformers need magnetic materials with good properties in the MHz regime. In this paper, we argue that available materials are not optimized for MHz power conversion applications—even those that are marketed as such—and that further development of magnetic materials is needed. In particular, we review how magnetic components are used in power converters and demonstrate that reducing core loss should be the main target of future material development, as existing permeabilities and saturation flux densities are substantially higher than necessary. The progress of power conversion technology will depend in part on how well new magnetic materials can be optimized—properly—for the MHz regime. Graphical abstract

Dynamic Hysteresis Modeling Taking Skin Effect Into Account for Magnetic Circuit Analysis and Validation for Various Core Materials

Abstract: This article presents a novel magnetic circuit model which can represent the dynamic hysteresis characteristics considering the skin effect. The proposed model is mathematically equivalent to the previously proposed magnetic circuit model incorporating the play model and Cauer circuit. However, the previous one has a problem in practical use that the magnetic circuit analysis must be performed by coupling with the external electric equivalent circuit to take the skin effect into account. Thus, it is difficult to apply the previous method to the analyses of devices with complicated shapes such as electric motors due to model complexity and convergence deterioration. On the contrary, the proposed model is more practical since it is composed of only the magnetic circuit elements. The calculation accuracy of the proposed model and its versatility for various kinds of core materials are experimentally proved by using ring cores made of grain-oriented (GO) and non-oriented (NO) silicon steels, an amorphous alloy, and a soft magnetic composite (SMC).

Development of Yokeless Axial Flux Machine Using 3D-Printed Shape-Profiled Core

Abstract: Today, Additive manufacturing (AM) offers more feasible solutions to the manufacturing and assembly of electrical machines with complex 3D designs such as axial flux motors. With particular focus on 3D printing of magnetic materials, this paper discusses the development of AM stator core for yokeless and segmented armature (YASA) axial flux machine. Aiming at high frequency core loss reduction, an AM shape-profiled core segment is proposed for a 10 kW YASA machine. Unlike the conventionally-stacked core, the proposed AM core has a better magnetic flux density distribution over its cross section, and consequently lower core losses. Using 3D printing technology, this design combines the manufacturing simplicity and high electromagnetic performance merits, allowing for higher-power density axial flux machines.

Fluorescent Single-Core and Multi-Core Nanoprobes as Cell Trackers and Magnetic Nanoheaters

Abstract: Iron oxide magnetic nanoparticles (MNPs) have been widely studied due to their versatility for diagnosis, tracking (magnetic resonance imaging (MRI)) and therapeutic (magnetic hyperthermia and drug delivery) applications. In this work, iron oxide MNPs with different single-core (8–40 nm) and multi-core (140–200 nm) structures were synthesized and functionalized by organic and inorganic coating materials, highlighting their ability as magnetic nanotools to boost cell biotechnological procedures. Single core Fe3O4@PDA, Fe3O4@SiO2-FITC-SiO2 and Fe3O4@SiO2-RITC-SiO2 MNPs were functionalized with fluorescent components with emission at different wavelengths, 424 nm (polydopamine), 515 (fluorescein) and 583 nm (rhodamine), and their ability as transfection and imaging agents was explored with HeLa cells. Moreover, different multi-core iron oxide MNPs (Fe3O4@CS, Fe3O4@SiO2 and Fe3O4@Citrate) coated with organic (citrate and chitosan, CS) and inorganic (silica, SiO2) shells were tested as efficient nanoheaters for magnetic hyperthermia applications for mild thermal heating procedures as an alternative to simple structures based on single-core MNPs. This work highlights the multiple abilities offered by the synergy of the use of external magnetic fields applied on MNPs and their application in different biomedical approaches.

Integrated Grid Inductor-Transformer Structure with Reduced Core Loss and Volume for E-Capless Single-Stage EV Charger

Abstract: This paper presents the design and optimization of an integrated magnetic structure that combines the grid inductors and transformer in the single-stage EV -charger. The proposed integration technique reduces the number of magnetic bodies, hence reducing the cost and total magnetic core loss while increasing the power density. By utilizing the fixed 50% duty cycle operation of the converter, a further reduction in core loss can be achieved resulting in improved light-load efficiency. This paper also presents an analysis of the optimal PCB winding arrangements for the proposed structure to achieve low winding AC loss and stray capacitance. To validate the proposed integrated magnetic structure, a 3.7 kW single-stage AC-DC converter prototype with four different cases of magnetic structures is built. Experimental comparison of these four cases shows that the proposed integrated magnetic structure has higher efficiency and power density compared to the non-integrated ones. U sing the proposed integrated magnetic structure, the core loss that dominates at light-load is improved resulting in an increase of efficiency by 0.9%. At the same time, the proposed integration technique reduces the number of magnetic cores as well as total core volume, reducing the cost and improving the converter power density by up to 11.1 %.