Optimizing Galvanic Isolation for DC-DC Push-Pull Converters: Insights into Transformer Design, Core Materials, and Wire Shapes

An investigation of nominal loss in 3%SiFe and amorphous of the transformer core materials will evaluate in this paper. The investigation involves the variation of power loss, flux leakage, and total harmonic distortion. The nominal loss has been measured using Epstein test frame with three layers of lamination. The loss in the amorphous transformer core material is 57.46% better than the transformer core with 3% SiFe material at flux density of 1.2T, 50 Hz. The flux leakage at corner in the 3% SiFe transformer core material is the lowest than the two of transformer core material, over the whole flux density range. Total harmonic distortion flux is the largest in the amorphous of transformer core materials and the smallest in the 3% SiFe of transformer core material. Using the amorphous material in transformer core is more efficient than the two of transformer core materials.

An investigation of nominal loss in 3%SiFe and amorphous of the transformer core materials will evaluate in this paper. The investigation involves the variation of power loss, flux leakage, and total harmonic distortion. The nominal loss has been measured using Epstein test frame with three layers of lamination. The loss in the amorphous transformer core material is 57.46% better than the transformer core with 3% SiFe material at flux density of 1.2T, 50 Hz. The flux leakage at corner in the 3% SiFe transformer core material is the lowest than the two of transformer core material, over the whole flux density range. Total harmonic distortion flux is the largest in the amorphous of transformer core materials and the smallest in the 3% SiFe of transformer core material. Using the amorphous material in transformer core is more efficient than the two of transformer core materials.

The article presents implementation of a computer application for current transformer design, based on classical methods, into the design of specific transformer. The transformer is produced with toroidal magnetic core, based on magnetic material with Flat hysteresis loop and provides galvanic separation in power electronic converters between the power and the control unit. In the previous works the basic requirements to soft magnetic materials for the toroidal magnetic core, design parameters as well the estimation of the current transformer errors are discussed. Also the computer aided design was described and illustrated with a part of the user interface. The new approach in the article is to incorporate a computer application for particular application - design of transformer that operates in current mode.

High-frequency transformer core materials are used in power converter applications due to high efficiency performance. Their volume and weight can be reduced when higher operating frequencies are used but at the expense of an increase in core material losses. Some studies analyzed transformer core material performance by using finite element method (FEM) analysis, while others used an experimental model. This study proposes an experimental approach to compare the high-frequency transformer efficiency performance of different core material types. In this way, newly produced core material performance can be rapidly analyzed by comparing it against a known core material type, thereby resulting in the fast identification of improved core material design. This empirical approach makes use of a standard half-bridge inverter topology to enable an analysis of high-frequency transformer core material efficiency performance. Actual voltage and current measurements are used to determine the efficiency and output power performance throughout a specified constant current load range at different switching frequencies. Initially commercial standard polycrystalline or ferrite E-core materials were used to validate the characterization jig performance measured curve trends. The usefulness of the jig is then demonstrated by comparatively analyzing and then verifying the expected performance difference between polycrystalline and nanocrystalline toroidal core materials.

Transformer in the Electrical network is the vital link between Generation, Transmission and Distribution. The magnetic circuit present forms the strategic link between primary and secondary. This link is due to the Electrical steel present in the Magnetic circuit, which is responsible for the flux linkage between the windings in the Transformers. The magnetic material used and its properties affects the efficiency of the Transformer. Due to high cost of Electrical steel, there are certain instances that inferior grade and core material from the dismantled Power Transformers are used in small rating Distribution Transformers affecting the reliability of the Distribution Network. The experimental study was conducted on 3 numbers of 25KVA Distribution transformers of identical designs are made with three different Cold Rolled Grain Oriented (CRGO) core material i.e., Prime CRGO material (New), Used CRGO core material (Removed from transformer after service of 20 years) and Mixed core (placing one new and one used lamination in alternating manner). This paper discusses the study on variation of Reactive Power consumption of different core materials and of the Distribution Transformers made with CRGO cores. And also, the changes in the Magnetizing Reactance in the Transformer. The Epstein results @ 1.5 tesla shows the deterioration in the magnetic properties for used core material as there is increase in reactive power. The transformer open circuit test results at 112% of rated voltages are very predominant in both Mixed and Used core transformer for Active and Reactive power. The results show that these transformers are probable to saturate at small changes in the voltages.

Magnetic core properties, core loss, permeability, and saturation magnetic induction of bcc-nanocrystalline Fe–M–B (M=Zr, Hf, and Nb) alloys produced by annealing a melt-spun amorphous phase were investigated in a ring-shaped form with the aim of clarifying the application potential as a core material. The bcc alloys exhibit high saturation induction (Bs) from 1.49 to 1.63 T combined with high permeability (μe) from 22 000 to 32 000 at 1 kHz and 0.4 A/m. The bcc Fe–M–B (M=Zr, Hf, or Nb) alloys also show low core losses (W) from 1.4×10−1 to 2.1×10−1 W/kg at 50 Hz and 1.4 T and from 1.70 to 2.50 W/kg at 1 kHz and 1.0 T. The W values attained for the bcc Fe–M–B (M=Zr, Hf, and Nb) alloys are smaller by 60%– 90% at 50 Hz and 1.4 T and 50%–70% at 1 kHz and 1.0 T, as compared with those for an amorphous Fe78Si9B13 alloy in practical use as a transformer core material. The low W values for the bcc-nanocrystalline alloys are presumably due to the small anomaly factor comparable to a Co-based amorphous alloy. The comparison of the present data with those for the amorphous Fe78Si9B13 alloy indicates that the bcc-nanocrystalline Fe–M–B (M=Zr, Hf, and Nb) alloys are promising for practical use as core materials.

Transformer design is critical as the demands on power converter efficiency and power density increase. Initial transformer core shape and size selection can be challenging, in many cases necessitating multiple elaborate design iterations to find a suitable core. A number of core constants have been proposed in the past to assist with initial core selection, however, most of them do not consider high frequency losses in transformer cores which are becoming increasingly important. The K gfe transformer design method is adapted in this paper to consider high frequency copper losses in transformer designs with bi-directional excitation and two windings. The presented expressions can be used to quickly determine the minimum achievable power losses for a given core size, material and wire diameter.

Design and analysis of a 35 kVA medium frequency power transformer with the nanocrystalline core material

Acoustic noise emission of transformers is mainly due to core vibration induced by reluctance force and magnetostriction which is highly dependent on the core material and geometry. This paper investigates the vibration and acoustic noise of nanocrystalline cores with different geometric shapes based on FEM simulation and experimental measurements. Furthermore, the optimal design of medium frequency transformers (MFT) by using different core materials and geometric shapes is analyzed to find the most suitable core for MFT design with high efficiency, high power density and low acoustic noise emission.

Redistributive balancing brings many benefits to electric vehicles, such as increased range and more uniform cell degradation. Despite previous analyses suggesting a 17-36% extension of battery lifetime, the cost of such systems has prevented the technology from being adopted in practice. This study proposes a simplified topology for battery-balancing auxiliary power modules with reduced magnetic material to achieve cost-friendly solutions without sacrificing functionality or balancing modes. The proposed system consists of a dual-active half bridge, halving the number of switches needed compared with the conventional dual-active bridge. In addition, the transformer core material is removed and a coreless transformer is used to provide isolation and energy transfer. Both changes reduce the cost of redistributive balancing. The topological modeling differs from cored transformer circuits as the coupling of the coreless transformer is weaker. The coupling coefficient is now used in an updated model that includes transformer currents and output powers. These, along with the balancing modes, are analyzed then experimentally verified. The proposed models can guide the selection of MOSFETs and the design of the coreless transformer. An analytic projection shows up to a 22% cost reduction compared with similar topologies.

Ferrite nanoparticles have invited enormous scientific attraction because of their unique properties and up-and-coming applications. The ferrites are used in filter circuits and core materials for transformers. In turn is designed for broadband spectrum and antenna material in the telecommunication industry, like radio, television, mobile communication, etc. Eddy current losses are minimal at high frequencies because of ferrites’ significantly high resistance; therefore, a variety of applications can be exploited at extremely high frequencies, unlike other magnetic components. For a variety of applications, different material properties are desired. Therefore, ferrites materials having different compositions are used. To prevent electromagnetic interference, ferrite cores are employed to block low-frequency noise and absorb high-frequency noise. Spinel ferrites are used in transformer cores, microwave devices, and high-frequency devices in the electronics sector. If their dielectric loss is low, ferrite nanoparticles can be used in switching inductors, antenna rods, and microwave devices. Ferrites are an excellent option for both traditional and contemporary applications owing to their variety of shapes, ongoing breakthroughs in material characteristics and cost-effectiveness. In this chapter, the properties of ferrite nanoparticles are discussed, which play an essential role in making ferrite usable in the telecommunication industry, e.g., elastic properties, such as hysteresis, coercivity, and magnetic saturation. The usages of ferrites in various components of telecommunication equipments are also discussed, including filter circuits, broadband and core of transformers.

As a result of advances in power electronics, in medium to high frequency high power conversion has become widespread. The performance and the sizing of the medium-frequency power transformer vary depending on material properties and operating frequency. While the core size determined by the power requirements, the specific core loss which varies depending on the frequency and the flux values becomes important. On the other hand, power handling capability of transformer varies according to the core material type and operation frequency. In this study, %3 SiFe 0.1mm material was compared with the nanocrystalline material for the medium-frequency transformer cores. SiFe and nanocrystalline core materials are modeled, tested and analyzed for the different frequency values. Thus, the relationship between the frequency increase with the power handling capability and core losses were uncovered.

PurposeThis paper aims to develop a model that reflects the current transformer (CT) core materials nonlinearity. The model enables simulation and analysis of the CT excitation current that includes the inductive magnetizing current and the resistive excitation current.Design/methodology/approachA nonlinear CT model is established with the magnetizing current as the solution variable. This model presents the form of a nonlinear differential equation and can be solved discretely using the Runge–Kutta method.FindingsBy simulating variations in the excitation current for different primary currents, loads and core materials, the results demonstrate that enhancing the permeability of the B–H curve leads to a more significant improvement in the CT ratio error at low primary currents.Originality/valueThe proposed model has three obvious advantages over the previous models with the secondary current as the solution variable: (1) The differential equation is simpler and easier to solve. Previous models contain the time differential terms of the secondary current and excitation flux or the integral term of the flux, making the iterative solution complicated. The proposed model only contains the time differential of the magnetizing current. (2) The accuracy of the excitation current obtained by the proposed model is higher. Previous models calculate the excitation current by subtracting the secondary current from the converted primary current. Because these two currents are much greater than the excitation current, the error of calculating the small excitation current by subtracting two large numbers is greatly enlarged. (3) The proposed model can calculate the distorted waveform of the excitation current and error for any form of time-domain primary current, while previous models can only obtain the effective value.

Various transformer core materials have been characterized in order to evaluate their potentialities for fabrication of electronic transformers capable of operating at elevated temperatures. Temperature and annealing time dependence of pertinent magnetic parameters such as saturation flux density, B s , permeability, μ, and hysteresis loss, W h , are reported here. Based on these investigations transformers employing Deltamax and 2V Permendur core materials have been built and they perform well at high temperatures. The maximum operating temperature for 2V Permendur transformers is about 500°C whereas for Deltamax transformers it is about 360°C.

In order to reduce energy losses of transmission and distribution systems, electric utility companies are demanding more efficient transformers from electrical equipment manufacturers. In response to this challenge, several new transformer core materials have been developed with the objective of reducing energy losses associated with AC magnetization. This paper will review the fundamentals of ferromagnetic domain wall motion and the relationship of this motion to energy losses during AC magnetization. Based on these fundamentals, two new approaches to low loss core materials will be discussed: (1) super-oriented silicon iron; (2) high saturation metallic glasses.