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This work proposes, analyzes, designs, and validates superior topologies of UHGH converters that are capable of supporting extremely large conversion ratios up to ∼2000× and output voltage up to ∼4-12 kV for future mobile soft robots from an input voltage as low as the range of a 1-cell battery pack. Thus, the converter makes soft robots standalone systems that can be untethered and mobile. The extremely large voltage gain is enabled by a unique hybrid combination of a high-gain switched magnetic element (HGSME) and a capacitor-based voltage multiplier rectifier (CVMR) that, together, achieve small overall size, efficient operation, and output voltage regulation and shaping with simple duty-cycle modulation. With superior performance, power density, and compact size, the UHGH converters prove to be a promising candidate for future untethered soft robots.

A DC‐DC converter with high boost and low switching voltage stress is proposed by combining switched capacitor (SC) and coupled inductor (CL) techniques based on a conventional boost circuit. The design methodology of this converter includes substituting SC for a single switch in the boost converter, combining CL, and integrating a resonant boost circuit for absorbing leakage inductance. The improved power switch topology in this design has lower voltage stress, lower diode current stress, fewer total components, and common ground than other conventional DC‐DC converters. The operating modes and steady state analysis of the converter are provided in terms of leakage inductance utilization, with component stress derivation and theoretical efficiency analysis. In addition, comparisons with other dc‐dc converters are made. Subsequently, experiments were conducted on a 200 W DC‐DC converter prototype to verify the reliability of the converter. [ABSTRACT FROM AUTHOR]

The paper deals with the dynamics of a resistance spot welding system. At the core of this system is a transformer, which is powered on the primary side by a pulse-width modulated inverter and has a full-wave output rectifier on the secondary side that provides a direct welding current. The entire system is nonlinear, due to magnetic hysteresis and electronics. The electronics prevent the current from flowing in all parts of the welding transformer at separate time intervals during the voltage supply period; therefore, not all the parameters affect the dynamic of currents and voltages all the time so the system is also time-variant. To design a high-performance welding system and to predict the maximum possible welding current at a specific load, it is necessary to know the welding and primary currents. The leakage inductances of the system can reduce the maximum welding current significantly at higher frequencies and the same load. There are several methods to determine these currents, each with its drawbacks. Measurements are time-consuming, using professional software is expensive and requires time to learn and free open-source software has many limitations and does not guarantee the correctness of the results. The article presents a new, fourth option—a theoretical derivation of analytical expressions that facilitate straightforward and rapid calculation of the welding and primary currents of the resistance spot welding system with symmetrical secondary branches. The derivation of the mathematical expressions is based on the equivalent circuits that describe the system in different operating states. The results of the numerical simulations confirmed the derived expressions completely. [ABSTRACT FROM AUTHOR]

The single-phase dual active bridge (DAB) DC/DC converter is a vital component in modern power electronics systems, facilitating efficient bidirectional power transfer between various energy sources and loads. One of the critical aspects in the design of such converters is the selection of an appropriate leakage inductance, as it significantly affects the circulating power within the converter. This study investigates the influence of inductance on the reactive power flow and introduces an analytical formula for calculating the necessary leakage inductance based on the specified rated power of the DAB converter. By employing the inductance values determined through the proposed formula, the developed power control-based modulation method, implemented in discrete time, successfully achieves zero reactive power caused by the first harmonic components under all load conditions. This selection of leakage inductance optimizes the performance of the converter ensuring efficient power delivery across various applications. The applicability of this method extends to various DAB applications, including electric vehicles, integration with asynchronous microgrids, and aerospace systems. [ABSTRACT FROM AUTHOR]

With the increasing complexity of power electronics converters, magnetic components like inductors, transformers in different configurations, etc., play important roles in shaping a power controller to meet its desired performance effectively and efficiently. Now, coupled inductors have emerged as one important category of magnetic components that can improve the performance of several types of power controllers used in different domains. They are used to improve the control response, reduce ripple content of output control variables, improve efficiency, enhance power density, etc. This review paper deals with coupled inductors in two ways. Firstly, it details the application prospects as well as design requirements for different applications of coupled inductors. Later, it deals with the design and practical validation of one coupled inductor essentially required for one complex application where the leakage inductance of each winding should be minimal. This review has analyzed that the magnetic circuit design would play a dominant role where both the soft magnetic material and winding layout would be extremely important. While designing a practical coupled inductor, this review article has further analyzed that a core material with low loss density, high saturation flux density and interleaved winding would make the ideal magnetic circuit. The proposed magnetic circuit has been thoroughly validated in a parametric-sensitive power controller for alternating current tungsten inert gas (AC TIG) welding.

Dual active bridge (DAB) converters are widely used in the on-board propulsion systems of transportation electrification applications. The tendency of decreasing volume consumption leads to the magnetic integration investigation of the planar transformers. For DABs, integration has been focused on integrating the series inductors and a high frequency transformer (HFT) into a single magnetic component by increasing the leakage inductance of the HFT. This brings a critical issue to the designers: whether structural modification is required for the selected core at the transformer design stage to achieve the aimed leakage inductance. Since equivalent series inductance in power characteristic is replaced by leakage inductance, e accurate leakage inductance estimation strategy is also required. This paper firstly proposed a reluctance based leakage inductance evaluation strategy for the accurate estimation with air-path leakage considered. As the common calculations of the winding-arrangement-dominated leakage inductance commonly ignores the air-path leakage fluxes. Based on the estimation of the threshold leakage inductance, an optimized magnetic integration procedure for planar transformer has been developed, which can help judge whether core modification is required and then provide winding arrangement coordination. 3D Finite Element Analysis (FEA) simulation and prototype experiments were conducted to validate the theoretical analyses.

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRAK Indonesia bertujuan untuk beralih dari bahan bakar fosil ke sumber energi terbarukan, dengan target integrasi sebesar 23% pada tahun 2025 dan 31% pada tahun 2050. Transisi ini menghadapi tantangan akibat sifat terputus-putus dari sumber energi terbarukan yang memengaruhi kualitas listrik. Solid State Transformer (SST) muncul sebagai solusi. Dalam penelitian ini, sebuah trafo frekuensi tinggi dirancang untuk konverter Dual Active Bridge (DAB), dengan leakage inductance menjadi parameter penting. Berdasarkan perhitungan yang dilakukan, menunjukkan kebutuhan leakage inductance adalah sebesar 277 uH untuk DAB. Untuk memenuhi kebutuhan daya dan nilai leakage inductance tersebut, trafo dengan inti EE48020, 87 lilitan non-seksional, dan ketebalan isolasi 8,4 mm dapat dikembangkan. Hasil simulasi mengkonfirmasi nilai leakage inductance yang dihasilkan sebesar 268,95 uH. Kata kunci: tranformator frekuensi tinggi, dual active bridge, solid state transformer, kebocoran induktansi, geometri inti ABSTRACT Indonesia aims to shift from fossil fuels to renewable energy sources, targeting 23% integration by 2025 and 31% by 2050. This transition faces challenges due to the intermittent nature of renewable sources, impacting power quality. Solidstate transformers (SST) emerge as a solution. In this study, a high-frequency transformer (HFT) is designed for the dual active bridge (DAB), with leakage inductance being a crucial parameter. Calculations indicate a 277 uH requirement for the DAB. To meet power needs and leakage inductance values, an HFT with an EE48020 core, 87 non-sectional turns, and 8.4 mm insulation thickness is developed. Simulation results confirm a leakage inductance of 268.95 uH for the HFT. Keywords: high frequency transformer, dual active bridge, solid state transformer, leakage inductance, core geometry

Introduction. The author examines the problem of improving the accuracy of computer simulation of electromagnetic processes of an auxiliary asynchronous motor of an electric locomotive with the frequency adjusted by an autonomous voltage inverter. The calculations of instantaneous motor phase currents were improved. The research justified the proposed adjustments to the computer model of a three-phase asynchronous motor to consider the skin effect in the stator and rotor windings, and the effect of the magnetic circuit saturation from leakage fluxes on the leakage inductance of the phases and, thereby, on the instantaneous phase currents. The model is necessary to enhance the reliability of the auxiliary electric drive of an electric locomotive through the correct selection of semiconductor switches for the electric motor inverter. Materials and methods. The researcher chose computer simulation using OrCAD as our research method, and the input data include experimental instantaneous phase voltages of the auxiliary asynchronous motor.Results. The article presents the results of adjusted computer simulations of instantaneous variables for steady-state engine operation and compares them with experimental data.Discussion and conclusion. The author compared the experimental and calculated data (phase current, torque, rotation speed of the auxiliary asynchronous motor of an electric locomotive) and substantiated the adjusted computer model to reduce errors in the calculation of electromagnetic processes of the electric motor. The adjusted computer model improves the accuracy of calculating the instantaneous phase currents of the motor. The calculations were performed for the steady-state operation of an asynchronous motor of the AZhV250M2RUHL2 type. The results show that the skin effect has the greatest influence on the leakage inductance of the stator winding.

The single-phase dual active bridge (DAB) DC/DC converter is a vital component in modern power electronics systems, facilitating efficient bidirectional power transfer between various energy sources and loads. One of the critical aspects in the design of such converters is the selection of an appropriate leakage inductance, as it significantly affects the circulating power within the converter. This study investigates the influence of inductance on the reactive power flow and introduces an analytical formula for calculating the necessary leakage inductance based on the specified rated power of the DAB converter. By employing the inductance values determined through the proposed formula, the developed power control-based modulation method, implemented in discrete time, successfully achieves zero reactive power caused by the first harmonic components under all load conditions. This selection of leakage inductance optimizes the performance of the converter ensuring efficient power delivery across various applications. The applicability of this method extends to various DAB applications, including electric vehicles, integration with asynchronous microgrids, and aerospace systems.

The performance and efficiency of high-frequency transformers (HFTs) are significantly influenced by leakage inductance. To improve the efficiency of HFTs, it is crucial to consider the effects of leakage inductance during the design and analysis processes. This research study aims to investigate a high-frequency toroidal transformer by examining different magnetic materials (Ferrite, Amorphas, and Iron-Powdered Alloy), winding configurations (solid, twisted, and LITZ wire), and operating frequencies (10 kHz and 50 kHz). To validate the effectiveness of parametric optimization in enhancing the system efficiency, the designed toroidal HFT was constructed and tested in a 600/300 V 3 kW dual active bridge (DAB) converter. The leakage inductances were measured using a frequency sweeping LCR meter. [ABSTRACT FROM AUTHOR]

This work proposes, analyzes, designs, and validates superior topologies of UHGH converters that are capable of supporting extremely large conversion ratios up to ∼2000× and output voltage up to ∼4–12 kV for future mobile soft robots from an input voltage as low as the range of a 1-cell battery pack. Thus, the converter makes soft robots standalone systems that can be untethered and mobile. The extremely large voltage gain is enabled by a unique hybrid combination of a high-gain switched magnetic element (HGSME) and a capacitor-based voltage multiplier rectifier (CVMR) that, together, achieve small overall size, efficient operation, and output voltage regulation and shaping with simple duty-cycle modulation. With superior performance, power density, and compact size, the UHGH converters prove to be a promising candidate for future untethered soft robots. [ABSTRACT FROM AUTHOR]

To ensure a reliable and stable power supply, optimal design and proper installation of the transformer are essential for the power suppliers and distributors. Short-circuit current is the main parameter of the transformer and causes the failure in the transformers. Accurate calculation and optimization of the leakage reactance help the transformer designers to mitigate against failure during the short circuit conditions. Transformer designers use different tapping positions for the manufacturing of the two-winding tap transformers. This study analysis and optimizes the leakage reactance of the two-winding tap transformer. Leakage reactance behavioral characteristics of the six different tappings are evaluated and examined in this study, including (1) without tapping, (2) upper tapping, (3) lower tapping, (4) middle tapping, (5) lower–upper tapping, (6) side tapping of the low voltage winding using finite element method. The results show that the side tapping has the least impact on the leakage reactance. The results also show that upper tapping and lower tapping have a significant effect on the leakage reactance. The comparison between the finite element method and experimental short-circuit test results for the optimized design also suggests that the finite element models can accurately evaluate the leakage reactance in the two-winding tap transformers.

Three-phase dual active bridge converters (DAB3) are a widely used topology in battery charging applications thanks to their numerous advantages, such as bidirectional power flow, galvanic isolation, low output current ripple, and inherent soft-switching. In such applications, three single-phase transformers are commonly employed as the AC-link to simplify manufacturing and reduce costs. These transformers' leakage inductance can be utilized instead of the external leakage inductance to achieve high power density. However, the assumption of uniformity in these inductances is not always accurate as they can vary significantly during fabrication. This study presents a comprehensive analysis of the impact of transformer leakage inductance variation, which can deviate by up to 24% from the desired value. The effects of this variation are investigated from different perspectives, including power transfer, soft-switching range, root-mean-square (RMS) current, and the temperature rise of the transformer winding. Although the power transfer and total copper loss of transformers are changed insignificantly even under highly mismatched leakage inductance, the currents and thermal distribution among phases are considerably impacted. Based on statistical probability, a maximum leakage inductance variation threshold of 10–15% compared to the desired value is recommended to ensure the maximum acceptable temperature rise among phases. Experimental results are presented to validate the analysis. [ABSTRACT FROM AUTHOR]

This paper focuses on the study of the high frequency transformer incorporated in solid- state transformers, specifically on the development of the steps that enable the design of an optimized high frequency transformer and its equivalent model based on the desired characteristics. The impact of operating a transformer at high frequency and the respective solutions that allow this impact to be reduced are analyzed, alongside the numerous advantages that the utilization of these transformers has over traditional 50/60 Hz transformers. Furthermore, the power scheme of the solid-state transformer is outlined, focusing on the power converters, which are immediately before and after the high frequency transformer (HFT). We also investigate a control technique that allows for correct operation and the existence of power bidirectionality. In a novel approach, this paper demonstrates the systematic steps for designing an HFT according to the desired specifications of each given project, helping students and engineers achieve their objectives in power-electronic applications. Moreover, this paper aims at increasing the knowledge of this area of power electronics and facilitating the development of new topologies with high power density, which are very important to the integration of renewable power sources and other applications. Finally, a simulation is presented to validate a high frequency transformer and its control technique. [ABSTRACT FROM AUTHOR]

In this paper, a modification of a conventional forward converter and a new mixed-stranded transformer winding technique are proposed for the development of a simple and high efficiency isolated dc-dc boost converter for solar photovoltaic applications. The conventional single switch forward converter topology is modified for simplification and elimination of losses due to the output filter components. A new mixed-stranded transformer winding technique is proposed to minimize the leakage inductance between the primary and tertiary windings for reducing losses. A pulse frequency modulation technique (PFM) is employed for reducing switching losses at low power operation. An experimental prototype of 300 W with a voltage step-up ratio of 1:12 has been built to obtain dc output voltage between 360-480 V for the dc input voltage of 30-40 V. Through the experimental results, it is shown that the converter can boost the input voltage according to the step-up ratio and exhibits a remarkably high dc-dc power conversion efficiency with a flat response curve. The average efficiency of around 95.5 % and peak efficiency of 97.6% are obtained. [ABSTRACT FROM AUTHOR]

To ensure a reliable and stable power supply, optimal design and proper installation of the transformer are essential for the power suppliers and distributors. Short-circuit current is the main parameter of the transformer and causes the failure in the transformers. Accurate calculation and optimization of the leakage reactance help the transformer designers to mitigate against failure during the short circuit conditions. Transformer designers use different tapping positions for the manufacturing of the two-winding tap transformers. This study analysis and optimizes the leakage reactance of the two-winding tap transformer. Leakage reactance behavioral characteristics of the six different tappings are evaluated and examined in this study, including (1) without tapping, (2) upper tapping, (3) lower tapping, (4) middle tapping, (5) lower–upper tapping, (6) side tapping of the low voltage winding using finite element method. The results show that the side tapping has the least impact on the leakage reactance. The results also show that upper tapping and lower tapping have a significant effect on the leakage reactance. The comparison between the finite element method and experimental short-circuit test results for the optimized design also suggests that the finite element models can accurately evaluate the leakage reactance in the two-winding tap transformers. [ABSTRACT FROM AUTHOR]

Due to the need for highly efficient and compact power electronic converters to operate at higher frequencies, traditional wire-wound magnetics are not suitable. This paper provides a comprehensive review of planar magnetic technologies, discussing their advantages as well as associated disadvantages. An extensive review of the research literature is presented with the aim of suggesting models for planar magnetics. Several strategies are proposed to overcome the limitations of planar magnetics, including winding conduction loss, leakage inductance, and winding capacitance. The goal of this study is to provide engineers and researchers with a clear roadmap for designing planar magnetic devices. [ABSTRACT FROM AUTHOR]

The leakage inductance of a transformer designed for a power electronic converter can drop significantly as the switching frequency is increased due to skin and proximity effects. Although the magnetic image method-based double-2-D model can predict the low-frequency leakage inductance of a partially-filled transformer with sufficient accuracy, it is inherently a frequency-independent model. While Dowell’s 1-D model uses frequency-dependent relations to account for both skin and proximity effects, its accuracy is severely affected by the assumed winding geometry. In this paper, a semi-analytical hybrid model is proposed that uses superposition to combine a modified Dowell’s model with the double-2-D model to predict the true leakage inductance of partially-filled transformers at any given frequency. All three conductor types—round, foil, and litz wire—are modeled and analyzed. The quasi-2-D model is further investigated on a variable inductance transformer (VIT) whose winding geometry can be modified mechanically to vary its leakage inductance. With less than 5% error throughout, the semi-analytically evaluated leakage inductances are in excellent agreement with the finite element method (FEM) simulated and experimentally measured leakage inductances.

Copyright of Electric Drive is the property of Electric Drive Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The leakage inductance of the transformer in a dual active bridge (DAB) dc–dc converter directly impacts the ac current waveforms and the power factor; thus, it can be considered a design requirement for the transformer. In the existing literature, a choice is made to either ensure soft switching in nominal power or to minimize the RMS current of the transformer. The inductance is typically obtained using optimization procedures. Implementing these optimizations is time-consuming, which can be avoided if a closed-form equation is derived for the optimum leakage inductance. In this paper, analytical formulas are derived to estimate the desired leakage inductance such that the highest RMS value of the current in the operation region of a DAB is kept to its minimum value. The accuracy and sensitivity of the analytical solutions are evaluated. It is shown that in a large design domain, the solution for the YY-connected MFT has a less than 3% error compared to the results obtained from an optimization engine. As an example of the importance of selecting the leakage inductance correctly, it is shown that for 11% deviations in the dc link voltages, a 10% deviation from the desired leakage inductance value can cause 2% higher RMS currents in the converter. [ABSTRACT FROM AUTHOR]

The use of coupled inductors in impedance source inverters improves the voltage gain performance at the expense of high dc-link voltage spikes and shoot-through (ST) currents. The result is an increase in voltage and current stresses on semiconductors, as well as reactive element capacity and overall losses. Thus, to overcome these problems, this letter proposes a new family of magnetically coupled impedance source inverters with a smooth dc-link voltage, a low ST current, and a higher voltage gain that are confirmed through experimental tests. [ABSTRACT FROM AUTHOR]

This work proposes, analyzes, designs, and validates superior topologies of UHGH converters that are capable of supporting extremely large conversion ratios up to ∼2000× and output voltage up to ∼4–12 kV for future mobile soft robots from an input voltage as low as the range of a 1-cell battery pack. Thus, the converter makes soft robots standalone systems that can be untethered and mobile. The extremely large voltage gain is enabled by a unique hybrid combination of a high-gain switched magnetic element (HGSME) and a capacitor-based voltage multiplier rectifier (CVMR) that, together, achieve small overall size, efficient operation, and output voltage regulation and shaping with simple duty-cycle modulation. With superior performance, power density, and compact size, the UHGH converters prove to be a promising candidate for future untethered soft robots.

The performance and efficiency of high-frequency transformers (HFTs) are significantly influenced by leakage inductance. To improve the efficiency of HFTs, it is crucial to consider the effects of leakage inductance during the design and analysis processes. This research study aims to investigate a high-frequency toroidal transformer by examining different magnetic materials (Ferrite, Amorphas, and Iron-Powdered Alloy), winding configurations (solid, twisted, and LITZ wire), and operating frequencies (10 kHz and 50 kHz). To validate the effectiveness of parametric optimization in enhancing the system efficiency, the designed toroidal HFT was constructed and tested in a 600/300 V 3 kW dual active bridge (DAB) converter. The leakage inductances were measured using a frequency sweeping LCR meter.

This paper presents a novel model for transformer windings to accurately represent the duality between electrical and magnetic circuits. The model can be used for the calculation of high-frequency transients in power systems and the design of high-frequency transformers, for example, those to be used in solid-state (utility-grade) transformers and power electronic converters. Existing circuit models do not consider the flux linkage in the winding thickness in a physical (dual) way. Duality is achieved by discretizing the winding thickness into thin sub-sections and distributing the proposed model building block across the winding. Analytical calculations are carried out to compare the accuracy of the proposed circuit for the computation of the terminal impedance, flux duality, and current distribution in the physical geometry of the winding. Further discretization is performed to extend the circuit to represent high-frequency phenomena: eddy currents and capacitive effects. The model can be easily implemented in any circuit simulation program using available circuit elements. The circuit parameters are computed with very simple expressions. The model is validated with finite element simulations. Differences of around 1% are obtained for relatively low model orders for high frequencies.

This article suggests a unified modeling approach to the analysis of tapped-inductor converters. The leakage inductance, inherent to coupled magnetic structures, and the associated snubber circuit effects were considered and incorporated into the suggested model. The proposed nonideal tapped inductor switcher model is formulated as an equivalent subgraph that can help to model most, if not all, converter topologies that comprise a two-winding tapped inductor. Both the continuous current mode and the discontinuous current mode were modeled. To validate the proposed approach, analysis of a Flyback converter with an RC snubber is presented. Theoretical prediction of the steady-state and small-signal behavior of the converters were confirmed by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This brief presents an optimal design of high power frequency transformer for flyback converter based on E-mode GaN device, which could be used in personal portable chargers. The new generation of wide band gap semiconductor GaN switch is used to improve the switching frequency of the circuit. The high-frequency magnetic core and the winding method of magnetic components are optimized. The leakage inductance of the transformer of magnetic components is greatly reduced. Consequently, the overall power density of the circuit is improved. The feasibility of the design scheme is verified by hardware implementation and experimental results. The test results show that compared with the traditional flyback magnetic element design, the volume of magnetic element is reduced by 30%. Meanwhile, the loss is reduced by 30%, and the peak efficiency of the converter can reach 94.2%. The ratio of leakage inductance of magnetic transformer to excitation inductance decreased from 2.2% to 1%. In addition, power density of the converter reached 20.26W/in3, which is much higher than the existing commercial ones. [ABSTRACT FROM AUTHOR]

In this manuscript, to increase the conversion efficiency of high current low voltage bidirectional DC/DC converter is proposed. The proposed converter uses switched inductor and switched coupled mutual inductance in the proposed system. Here, the switched inductor is an impedance network consists of split inductors and switches, which provides the high voltage conversion ratio and improves the output power quality that need for the low voltage applications. It also used as a filter to circulate the high frequency switching harmonics. In the proposed circuit, leakage current and power loss of mutual inductance is decreased because of soft switching. Thus the proposed method helps to reduce the switching loss, possibly low electro magnetic interference (EMI) and easier thermal management. This is used in the development of light-load competence of power conversion of DC/DC converter. The proposed work performed using MATLAB/Simulink platform. Finally, the conversion efficiency of proposed high current low voltage DC/DC converter is compared with classical circuit. [ABSTRACT FROM AUTHOR]

Leakage inductance is one of the key parameters of a transformer, and it is often intentionally integrated into transformers. Rogowski's equation is generally used for leakage inductance calculation; however, it is only applicable to concentric winding transformers where windings have the same height. Consequently, it has limited applications. This paper proposes a transformer leakage inductance calculation method using a double Fourier series. The limitation of Rogowski's leakage inductance equation was analyzed in practical applications, and a new model for calculating the leakage inductance of a double-group-overlapping winding transformer was derived. Experimental prototypes of transformers were developed, and their simulation models were built in Ansys. The correctness of the proposed calculation method for transformer leakage inductance using a double Fourier series was verified by comparing the calculation results with the simulation and measured ones. A sensitivity analysis was also conducted by studying the variations in different parameters that might affect the leakage inductance value. The proposed calculation model gives an intuitive and simple method with less calculation and design effort while maintaining reasonable accuracy for leakage inductance calculation. In addition, the featured double Fourier series approach has a wider range of applications than Rogowski's equation. [ABSTRACT FROM AUTHOR]

High-frequency transformers are becoming an essential component in the integration of power resources that rely on power electronic converters; their efficiency and performance are influenced by parasitic characteristics in the interface. In this article, the design of a high-frequency toroidal transformer has been explained in detail using the ANSYS Maxwell platform. Various parameters, such as leakage inductance, magnetic flux density, magnetic field strength and uniform magnetic flux line are analyzed using Finite element analysis. High-frequency transformers using a toroidal core with different winding configurations are examined and all parameters obtained through simulation are validated by an analytical approach. Analysis of each design is based on its leakage inductances, which will aid in the appropriate selection of transformers as a function of their operating frequency. This analysis is expected to guide designers to optimize the high-frequency transformer parameters based on practical applications. The optimized parameters are then applied for a dual active bridge (DAB) converter within MATLAB/Simulink to verify the design process. A prototype has been built to validate the simulation and design procedure. The results obtained from both simulation and experiments are compared and show great correlation. [ABSTRACT FROM AUTHOR]

A high voltage gain single switch DC-DC converter with efficient leakage energy recovery is presented in this brief. Effective leakage energy recycling is an important requirement in this class of converters with coupled inductors to overcome the high voltage stress across semiconductor devices. The proposed converter effectively recycles the leakage energy of the coupled inductor through a passive clamp circuit to the load. Hence, the efficiency of the converter is improved considerably. The proposed converter has the lowest switch voltage stress among other similar topologies, thereby making it feasible to select a low rating switch for the same boost gain. The converter has a lower sum of diode voltage stress and improved reverse recovery performance of the output side diode as well. The converter performance has been evaluated on the basis of different factors like efficiency, switch voltage stress, diode voltage stress, etc. The proposed converter performance is compared with that for various competitive topologies and is observed to be performing better. The effect of leakage inductance variation is studied on the gain of the converter. The proposed concept is verified via simulation and experimental prototype. [ABSTRACT FROM AUTHOR]

With an objective to accurately characterize the leakage inductances and winding resistances of a high-frequency planar transformer (HFPT) for a 500 kHz resonant CLLC converter, this article elucidates the correlation between various specifications involved in hardware fabrication of various winding configurations and their structural dependence on the resultant parameters. A precise analytical model is developed using 3-D finite element analysis (FEA) to synthesize the effective magnetic field and current density distribution in fabricated winding structures. Furthermore, a thorough analysis to study the interdependence of the resultant parameters on specifications such as printed circuit board (PCB) thickness and its fabrication layout, air gaps, and conductor thickness is presented for various winding configurations, thus elucidating various design-based tradeoffs. Also, frequency dependence of the obtained parameters is described which validates the optimal selection of winding configuration based on the effective gain magnitude for the CLLC converter topology. Detailed comparison between the developed analytical model with simulation model developed in Maxwell3-D and fabricated winding structures is presented, and the results validate the model accuracy, portraying an average mismatch of 3.8% and 6.2%, respectively. [ABSTRACT FROM AUTHOR]

Inductance is one of the main parameters directly related to the reactive powers of Shunt Reactors (SRs) in electrical systems. Thus, the definition and computation of leakage inductances and the ratio of leakage to total inductances play an extremely important role in the design and manufacturing of SRs. In this study, a finite element approach was developed to compute leakage and total inductances and define a relationship between them with different SR powers and high voltage levels. The expanded method is presented with the magnetic vector potential formulations. [ABSTRACT FROM AUTHOR]

Due to the need for highly efficient and compact power electronic converters to operate at higher frequencies, traditional wire-wound magnetics are not suitable. This paper provides a comprehensive review of planar magnetic technologies, discussing their advantages as well as associated disadvantages. An extensive review of the research literature is presented with the aim of suggesting models for planar magnetics. Several strategies are proposed to overcome the limitations of planar magnetics, including winding conduction loss, leakage inductance, and winding capacitance. The goal of this study is to provide engineers and researchers with a clear roadmap for designing planar magnetic devices.

In this study, a design methodology and a software based on this methodology for single and three-phase iron-core shunt-reactors are introduced. The software, which performs analytical calculations and optimization of the target reactor under design, in accordance with the pre-determined criteria by the user such as input data, assumptions and design criterion, is developed for both single and three-phase reactors in Matlab/GUIDE environment. Several reactor designs with different power and voltage levels are performed by means of the developed software and accuracy tests are carried out by Ansys/Maxwell finite element analyses. Results show that; the proposed design methodology is fast, accurate and reliable for iron core shunt reactor design. In addition, since there is no introduced clear cut design methodology and software in the literature, the proposed study may have an important contribution in the field. [ABSTRACT FROM AUTHOR]

A novel magnetic integrated controllable reactor of transformer type (CRT) has the advantages of simple structure, flexible assembly, convenient maintenance and practicability. To analyze its operation characteristics accurately, we establish corresponding equivalent mathematical model considering magnetic leakage based on magnetic circuit and circuit dualistic Transformation method. The distribution of magnetic leakage field of each winding is analyzed qualitatively, and the analytical calculation formulas of magnetizing inductance and leakage inductance of each winding are derived. Based on this, the analytical calculation formulas of short-circuit impedance and winding current of CRT under different working conditions are derived. The field-court coupling finite element model of the magnetic integrated CRT is established to simulate the current of each winding under different working conditions. The results show that the analytical calculation results of each winding current have good consistency with the finite element calculation results, indicating the validity of CRT equivalent mathematical model and correctness of the analytical formulas of leakage inductance, short-circuit impedance and winding current of CRT. The working winding current of CRT is increasing gradually with the operation of control winding in turn to realise the transition of CRT compensation capacity from zero to a rated value. [ABSTRACT FROM AUTHOR]

This paper presents an accurate analytical method for calculating the leakage inductance of shell-type E-core transformers with rectangular windings. For this purpose, first, an expression for calculating the leakage inductance per unit length inside the core window considering the core walls as the flux-normal boundary condition is derived. Then, a new accurate method for determining the Mean Length of Turns (MLT) based on the total stored energy is presented. The MLT is needed for the leakage inductance calculation using 2-D methods. By dividing the MLT into three partial lengths and calculating the corresponding leakage inductances using three different core window arrangements, the effect of core structure on the total leakage inductance is considered. The method is verified by 3-D FEM simulations as well as the leakage inductance measurements on two different fabricated transformer prototypes. The superiority of the method is also confirmed by comparisons with the previous analytical approaches. The proposed method enables the leakage inductance calculation with an error less than 1%, compared to the 3-D FEM results. Using the presented method, the leakage inductance calculations can be performed rapidly and accurately in the design stage without the need for time-consuming 3-D FEM simulations.

The leakage field in shell-type transformers is strongly affected by the boundary conditions introduced by the core walls and thus the effect of the core should be considered properly in the leakage inductance calculation. In this paper, a new method for accurate calculation of the leakage inductance of shell-type multi core-segment transformers with circular windings is presented. For this purpose, first, the expressions for self and mutual inductances are derived in cylindrical coordinates considering the core walls as the flux-normal boundary condition. Then, a new approach is proposed for calculating the leakage inductance considering the number and dimensions of the used core segments. The method is developed at first for single and double core-segment transformers (known also as E-core and U-core transformers) and then adopted for shell-type segmented-core transformers. The method is verified by 3-D FEM simulations. The comparisons with the previous analytical methods demonstrate the superiority of the proposed method. A transformer prototype has been built and verification tests have been conducted. The comparisons show that the leakage inductance can be estimated with an error less than 1%, demonstrating a very high accuracy with the proposed method.

In this paper, an integrated transformer design methodology for dual-active-bridge (DAB) converters, which basically utilize leakage inductance so as to substitute a cumbersome inductor in the conventional DAB converters, is newly proposed. The proposed integrated transformer with integrated leakage inductance inherently includes leakage inductance and magnetizing inductance, whose values can be appropriately selected by modulating the number of turns and the center-core air-gap. Based on the theoretical analysis of the DAB converters, the major parameters, i.e., primary and secondary current levels and its phase difference, can be derived, and these values are utilized for magnetic analysis of the proposed integrated transformer. Considering core loss and copper loss of the proposed integrated transformer in the DAB converters, optimal values of the center-core air-gap $l_{g}$ and the optimal number of turns $N_{\mathrm {1,}op} ~\&~ N_{\mathrm {2,}op}$ can be determined so that high power efficiency is achieved at a normal operating point of the DAB converters. The 20W prototypes of the DAB converter with EER2834 and EER3019 of the ferrite cores were fabricated and verified by simulation and experiment. The design results showed that the optimal number of turns at $l_{g} =2.0$ mm are found to be 11 and 10, for the EER2834 and EER3019, respectively. Compared to 94.5% and 96.3% of AC efficiencies for the conventional transformer and inductor set, the proposed integrated transformer achieved 95.8% and 96.9% of AC efficiencies at maximum power transfer point of $\theta _{p} = \pi $ /2 for EER2834 and EER3019, respectively.

This article presents a novel modulation scheme for device voltage stress mitigation and comprehensive analysis of the impact of transformer leakage inductance in a current-source solid-state transformer (SST). Different from dual active bridge (DAB) SST, the operation of the current-source SST is similar to that of a flyback converter. The device bridge on only one side of the transformer is active to store energy into or release energy from the magnetizing inductance which acts as a current-source dc-link. Such flyback operations with reverse-blocking switches can lead to additional device voltage stress and incomplete zero-voltage switching (ZVS) on the current-source soft-switching solid-state transformer (S4T) under conventional modulation. A new modulation scheme is proposed to address this issue. Moreover, different from the DAB, the leakage inductance of the medium-frequency transformer (MFT) in the S4T is a parasitic element similar to that in a matrix SST and can cause additional device voltage stress. Though the resonant capacitors, originally added to achieve ZVS, can absorb and recycle the leakage energy in the S4T, these capacitors need to be increased with larger leakage inductances to limit the voltage stress. However, large resonant capacitors can result in more lost duty cycles and reduced efficiency. The impact of such leakage inductance on device voltage stress is analyzed comprehensively, which is critical to guide future research and design of the S4T. Experimental results from S4T prototypes for dc–dc, multiport ac–dc, and ac–ac conversion with 1:1 and 4:1 MFT comprehensively verify the proposed concepts. Finally, a case study of a three-phase ac–ac S4T over a power range from 1 to 100 kVA each module reveals that the MFT leakage inductance should be less than 1% of the magnetizing inductance for safe operation. [ABSTRACT FROM AUTHOR]

In order to improve the step-up capability of the Zeta converter, the method of topology combination and coupled voltage doubler is used to combine the Zeta converter with a diode-capacitor multiplier while adding a coupled inductor structure. A high-gain combined Zeta converter with coupled inductor is proposed. This converter has a higher voltage gain, and the shared capacitor-diode structure in the structure absorbs the leakage inductance energy for the passive clamp branch. The working principle of the converter is analyzed, and the voltage gain expression of the converter and the voltage stress expression of the device are derived. The results show that the proposed converter has the highest voltage gain and the lower voltage stress. The capacitor-diode structure in the shared structure acts as a passive clamping branch, absorbing the leakage inductance energy without adding additional devices. The correctness of the theoretical analysis is verified by setting up 150 W experimental prototype. [ABSTRACT FROM AUTHOR]

The magnetically coupled three‐phase dual‐active‐bridge (DAB3) DC‐DC converter is highly suitable for high‐power applications. Although the converter has many advantages, the structure, working mode and electromagnetic effect of its key magnetic component—high‐power medium‐frequency three‐phase transformer (MFT3) is more complex, and the capacity, frequency, loss, temperature rise and leakage inductance restrict each other, forming a complex and systematic design problem. This paper focuses on the overall design method and performance of high‐power MFT3. Based on the analysis of steady‐state voltage and current waveforms of DAB3 converter, the expression of harmonic current is derived by using fundamental wave analysis, and the analytical calculation method of copper loss is proposed. According to the piecewise linear flux density waveform excited by six‐step voltage wave, the modified IGSE method is proposed to calculate the core loss. For MFT3 with three‐phase five column core topology, a lumped parameter thermal network model with 14 temperature nodes is established to obtain the temperature rise. The influence of winding arrangement on leakage inductance is analyzed, and the analytical expression of leakage inductance is presented. On this basis, the design method of high‐power MFT3 is proposed based on the free parameter scanning method. A 5 kHz, 15 kW MFT3 model with the nanocrystalline core material is made, and the leakage inductance, core loss, copper loss and temperature rise are extracted by finite element method (FEM) and experiment. The effectiveness of the proposed method is verified by comparing the design results with the FEM simulation and experimental results. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Y-Source Impedance Network (YSN) is one of the most suitable for providing high voltage gain. It generatesa high voltage gain by using a small shoot-through duty cycle, which makes it suitable in applications require a wide range of input voltages such as the Photovoltaic (PV) power plants. However, traditional (YSNs) are unable to boost low voltages in certain applications to the DC-link voltage (about 400V) since it requires a high number of the turns ratio. Higher turns ratio implies higher leakage inductance resulting in higher DC-link voltage spikes. Also, traditional YSNs have high voltage stresses across the components. In this paper, a developed new transformerless Micro-Inverter (MI) is presented that can overcome all the aforementioned drawbacks. The proposed MI has been developed and designed to eliminate both the leakage inductance due to three-winding coupled transformer and leakage current due to using transformerless MI configuration. In addition, the proposed MI reduced the components' stress significantly and increases the converter voltage gain capability in one single-stage. The proposed high boost ratio transformerless MI is analyzed through the PLECS software simulator and implemented in a small scale MI prototype to ensure the results agree with the analysis and simulation results

Determination of the parameters of the transformer circuit is a very important task, as there are a huge number of them (transformers), of different power, different designs, performing different tasks, working in different conditions at voltages and currents of different frequencies and form. This article deals with the determination of the parameters of greatest interest, the parameters that take into account the phenomena in the magnetic core, and the active resistances of the windings, which are calculated for the increased frequency (up to 30 MHz), implemented in secondary power supplies and other semiconductor devices.

The leakage inductance of the transformer in a dual active bridge (DAB) dc–dc converter directly impacts the ac current waveforms and the power factor; thus, it can be considered a design requirement for the transformer. In the existing literature, a choice is made to either ensure soft switching in nominal power or to minimize the RMS current of the transformer. The inductance is typically obtained using optimization procedures. Implementing these optimizations is time-consuming, which can be avoided if a closed-form equation is derived for the optimum leakage inductance. In this paper, analytical formulas are derived to estimate the desired leakage inductance such that the highest RMS value of the current in the operation region of a DAB is kept to its minimum value. The accuracy and sensitivity of the analytical solutions are evaluated. It is shown that in a large design domain, the solution for the YY-connected MFT has a less than 3% error compared to the results obtained from an optimization engine. As an example of the importance of selecting the leakage inductance correctly, it is shown that for 11% deviations in the dc link voltages, a 10% deviation from the desired leakage inductance value can cause 2% higher RMS currents in the converter.