The Experts below are selected from a list of 3048 Experts worldwide ranked by ideXlab platform
Torbjorn Thiringer - One of the best experts on this subject based on the ideXlab platform.
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an accurate analytical method for Leakage Inductance calculation of shell type transformers with rectangular windings
IEEE Access, 2021Co-Authors: Morteza Eslamian, Mohammad Kharezy, Torbjorn ThiringerAbstract: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.
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optimum Leakage Inductance determination for a q2l operating mmc dab with different transformer winding configurations
2019 20th International Symposium on Power Electronics (Ee), 2019Co-Authors: Babak Alikhanzadeh, Torbjorn Thiringer, Mohammad KharezyAbstract:This paper discusses the procedure for the determination of the optimum Leakage Inductance of a medium frequency transformer (MFT) for a quasi-two-level (Q2L) operating three-phase modular multilevel converter dual-active bridge (MMC-DAB) considering the effects of the MFT winding configuration. Three different winding configurations-namely, Y-Y, D-D, and Y-D-are considered for the connection of the MFT windings. The optimum Leakage Inductance requirement of the MFT, the currents total harmonic distortion (THD), and the transformer utilization factor (TUF) are compared for the three winding configurations. It is found that the Y-Y and the D-D configurations have similar optimum Leakage Inductance patterns, which are different from the Y-D configuration. Furthermore, it is established that an optimized Leakage Inductance value for a conventional DAB, can be utilized for the Q2L-operating MMC-DAB for a wide range of transition time with the Y-Y and the D-D winding configurations if less than a 5% error could be tolerated in its value. A comparison with respect to the TUF and the currents THD revealed that the Y-Y and the D-D configurations result in a higher TUF compared to the Y-D configuration; However, the Y-D configuration has approximately two times lower currents THD compared to the other two configurations.
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calculation of the Leakage Inductance of medium frequency transformers with rectangular shaped windings using an accurate analytical method
European Conference on Power Electronics and Applications, 2019Co-Authors: Morteza Eslamian, Mohammad Kharezy, Torbjorn ThiringerAbstract:To achieve the lowest loss by the Zero-Voltage Switching of a Dual Active Bridge converter, it is crucial to precisely calculate the embedded Leakage Inductance of the used Medium Frequency Transformer (MFT). An effective analytical method is proposed for calculation of the Leakage Inductance of the MFT with rectangular-shaped windings.
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accurate evaluation of Leakage Inductance in high frequency transformers using an improved frequency dependent expression
IEEE Transactions on Power Electronics, 2015Co-Authors: Amin M Bahmani, Torbjorn ThiringerAbstract:Moving toward higher power density in magnetic components, which is often realized by increasing the operating frequency, leads to the need for development of more accurate design tools, for example, more accurate expressions for core losses, winding losses, and Leakage Inductance calculations. This paper presents a new analytical expression intended to accurately evaluate the Leakage Inductance of transformers in the high-frequency range in which the behavior of the magnetic field within the windings is altered. Unlike conventional expressions, which usually overestimate the Leakage Inductance at higher frequencies, this expression accounts for high-frequency behavior of the magnetic field and provides high accuracy when operating at high frequencies. These high accuracy and applicability makes the derived expression of interest for designers to avoid time consuming finite-element simulations without compromising with accuracy. The expression is validated by 2-D finite-element method simulation, as well as by measurements.
Alireza Khaligh - One of the best experts on this subject based on the ideXlab platform.
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planar transformer with asymmetric integrated Leakage Inductance using horizontal air gap
IEEE Transactions on Power Electronics, 2021Co-Authors: Michael Dantonio, Shiladri Chakraborty, Alireza KhalighAbstract:This article presents a novel planar-based transformer winding and core structure with controllable Leakage Inductance generation for integrated magnetics applications. As a result of limitations in integrated magnetics from the literature, a new approach is proposed utilizing semi-interleaved windings and controllable Leakage via a Leakage flux core leg featuring a horizontal air gap. The proposed transformer design is analyzed via detailed reluctance modeling to determine closed-form equations for the magnetizing and asymmetrically distributed Leakage Inductances. Next, a genetic-algorithm-based multiobjective design optimization problem is developed, seeking to minimize the core and winding losses of the proposed transformer subject to a set of parametric and geometric constraints in a dc–ac dual-active-bridge topology for microinverter applications. The optimization was extended to include other integrated magnetic structures from the literature, where it is determined that the proposed transformer is superior from the perspectives of efficiency, footprint area, and parasitic capacitance. Based on the results of the optimization analysis, two designs with theoretical transformer California Energy Commission (CEC) efficiency drops (i.e., CEC efficiency reduction specifically due to the transformer loss mechanisms) of 1.19% and 0.83% were fabricated and evaluated for electrical and thermal performance in the proposed 40 V, 400 W microinverter.
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planar transformer with asymmetric integrated Leakage Inductance using horizontal air gap
IEEE Transactions on Power Electronics, 2021Co-Authors: Alireza Khaligh, Michael Dantonio, Shiladri ChakrabortyAbstract:This manuscript presents a novel planar-based transformer winding and core structure with controllable Leakage Inductance generation for integrated magnetics applications. As a result of limitations in integrated magnetics from the literature, a new approach is proposed utilizing semi-interleaved windings and controllable Leakage via a Leakage flux core leg featuring a horizontal air gap. The proposed transformer design is analyzed via detailed reluctance modeling to determine closed-form equations for the magnetizing and asymmetrically distributed Leakage Inductances. Next, a genetic-algorithm-based multi-objective design optimization problem is developed, seeking to minimize the core and winding losses of the proposed transformer subject to a set of parametric and geometric constraints in a DC-AC dual-active-bridge topology for microinverter applications. The optimization was extended to include other integrated magnetics structures from the literature, where it is determined that the proposed transformer is superior from the perspectives of efficiency, footprint area, and parasitic capacitance. Based on the results of the optimization analysis, two designs with theoretical transformer CEC efficiency drops (i.e. CEC efficiency reduction specifically due to the transformer loss mechanisms) of 1.19% and 0.83% were fabricated and evaluated for electrical and thermal performance in the proposed 40 V, 400 W microinverter.
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high power density high efficiency llc converter with an adjustable Leakage Inductance planar transformer for data centers
Iet Power Electronics, 2019Co-Authors: Ayan Mallik, Gary Cooke, Alireza KhalighAbstract:LLC converters can achieve high efficiency, high- power density, wide gain range, and galvanic isolation. This study presents a high-power-density and high-efficiency LLC converter with an adjustable-Leakage-Inductance planar transformer for the DC-DC conversion in data center power supplies. A planar transformer with adjustable Leakage Inductance is modelled and developed to provide an accurate design for resonant frequency and voltage gain. A detailed power loss analysis is performed. Furthermore, a thermal model is provided to aid in heat sink design. GaN devices are used in the converter to achieve high-switching frequency and low-switching loss. A 450 kHz, 360-400 V DC input, 12 V DC output, 750 W LLC converter prototype with an adjustable-Leakage-Inductance planar transformer is built and tested. The power density of the system is 15.4 W/cm 3 including an auxiliary power supply. The peak efficiency of the overall system is over 95%.
Khairul Safuan Muhammad - One of the best experts on this subject based on the ideXlab platform.
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magnetically isolated gate driver with Leakage Inductance immunity
IEEE Transactions on Power Electronics, 2014Co-Authors: Khairul Safuan MuhammadAbstract:This letter presents the design of a magnetically isolated gate driver with high immunity to Leakage Inductance. The proposed gate driver (PGD) is developed based on a bipolar totem-pole gate driver (noninverting) located on the secondary side of the coupling transformer. It is able to drive a MOSFET/IGBT from standard CMOS to TTL output and down to LSTTL level. It also achieves large duty cycle ratio and small input to output delay and provides reliable isolation. In this letter, the PGD is analyzed and verified experimentally. The design guidelines are also provided including design considerations.
W G Hurley - One of the best experts on this subject based on the ideXlab platform.
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improved analysis and modeling of Leakage Inductance for planar transformers
IEEE Journal of Emerging and Selected Topics in Power Electronics, 2019Co-Authors: Ziwei Ouyang, W G Hurley, Michael A E AndersenAbstract:Planar transformers have often been mistaken to essentially have lower Leakage Inductances. The “radial effect” is a natural characteristic for planar windings due to a higher aspect ratio of conductor width to conductor thickness, which gives a reduction in Leakage Inductance. Traditional formulas for Leakage Inductance in traditional transformers, where the winding width is much smaller than the winding height, are not suitable for planar transformers. This paper specifically tailors the traditional 1-D solution of Leakage Inductance by decomposing the Leakage flux into longitudinal and transversal fluxes. In this manner, the “eddy current effect” and the “radial effect” in Leakage Inductance can be analyzed individually. The proposed new formula including both ac (high-frequency eddy current effect) and dc effects (radial effect) offers an accurate prediction of Leakage Inductance in planar transformers. Finite element analysis and measurements are carried out to validate the proposed formula.
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calculation of Leakage Inductance for high frequency transformers
IEEE Transactions on Power Electronics, 2015Co-Authors: Ziwei Ouyang, Jun Zhang, W G HurleyAbstract:Frequency-dependent Leakage Inductance is often observed. The high-frequency eddy current effects cause a reduction in Leakage Inductance. The proximity effect between adjacent layers is responsible for the reduction of Leakage Inductance. This paper gives a detailed analysis of high-frequency Leakage Inductance and proposes an accurate prediction methodology. High-frequency Leakage Inductances in several interleaved winding configurations are also discussed. Interleaved winding configurations actually give a smaller degree of reduction of Leakage induction at high frequency. Finite-element analysis simulation and measurement validate the models.
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Leakage Inductance calculation for planar transformers with a magnetic shunt
Energy Conversion Congress and Exposition, 2013Co-Authors: Jun Zhang, Ziwei Ouyang, Maeve Duffy, Michael A E Andersen, W G HurleyAbstract:The magnetic shunt is generally inserted in a planar transformer to increase the Leakage Inductance which can be utilized as the series inductor in resonant circuits such as the LLC resonant converter. This paper presents a calculation methodology for the Leakage Inductance of the transformer with a magnetic shunt by means of the stored magnetic energy in the primary and secondary sides of the transformer using the magnetomotive force (MMF) variation method, as well as the stored energy in the shunt based on the reluctance model. The detailed calculation method is described. Both the FEA simulation and the experimental results have proven the validity of the proposed calculation method for Leakage Inductance.
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calculation of Leakage Inductance in transformer windings
IEEE Transactions on Power Electronics, 1994Co-Authors: W G Hurley, D J WilcoxAbstract:A formula is presented to calculate mutual impedance between transformer windings on ferromagnetic cores. The formula is based on the solution of Maxwell's equations for coils on ferromagnetic cores and as such offers the ultimate in accuracy. The formula is frequency dependent, taking into account the effect of eddy currents in the core on the flux distribution as well as representing the eddy current core loss as an equivalent resistance. Experimental results are presented for Leakage Inductance and an illustrative example is presented showing how Leakage Inductance affects the operation of a typical switching mode power supply. Approximations for the formula are also presented to simplify the calculations under certain operating conditions. >
Eiji Hiraki - One of the best experts on this subject based on the ideXlab platform.
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effects of secondary Leakage Inductance on the llc resonant converter
IEEE Transactions on Power Electronics, 2020Co-Authors: Mostafa Noah, Tomohide Shirakawa, Kazuhiro Umetani, Jun Imaoka, Masayoshi Yamamoto, Eiji HirakiAbstract:It is quite often to utilize the transformer Leakage Inductance in the resonant tank of the LLC resonant converter to allow for a drastic reduction in the converter cost, weight, size, and volume. The effects of the secondary Leakage Inductance on the operation of the LLC resonant converter are not well discussed in the relevant literature, and it is the purpose of this paper to give an insight into these effects. The contribution of this paper lies in the following: first, highlighting that it is not always an accurate assumption to consider that the values of the primary and secondary Leakage Inductance are identical, specifically in asymmetric magnetic core structures. Second, it has been disclosed that the well-known coupling factor ( k 12) cannot properly express the unequalized Leakage Inductance distribution in the proposed asymmetric transformer. Therefore, the authors bring the primary coupling factor ( k 1) and secondary coupling factor ( k 2) into practice to appropriately express the unequalized Leakage distribution on the primary and secondary windings, which can be controlled by the allocation of the relevant winding with respect to the air gap, utilizing the noise absorber, and changing the distance between the winding. Several transformer prototypes had been built and experimentally tested to validate these hypotheses. Third, it has been observed that the transformer voltage gain and efficiency can be improved when the transformer Leakage Inductance is concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current $(i_{m})$ , especially at the light load condition. Fourth, it has been reported that in a transformer structure with a concentrated value of Leakage on the secondary side would decrease the resonant tank input impedance, vertically widen the voltage–gain curve of the converter, and eventually increase the frequency control bandwidth with respect to the load variation. Transformer prototypes had been constructed and tested in a 390 V/12 V–220 W LLC resonant converter to evaluate the proposed analysis.
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effects of secondary Leakage Inductance on the llc resonant converter part i transformer voltage gain and efficiency
Applied Power Electronics Conference, 2019Co-Authors: Mostafa Noah, Tomohide Shirakawa, Kazuhiro Umetani, Jun Imaoka, Masayoshi Yamamoto, Eiji HirakiAbstract:Minimizing the transformer magnetizing Inductance is essential for the soft switching operation of the LLC resonant converter, despite the fact that it results in higher values of magnetizing current, which deteriorates the converter efficiency. Furthermore, it is a well-known practice to utilize the transformer Leakage as an inductive component in the resonant tank to improve the power destiny. This paper reveals that the transformer voltage gain can be improved when the transformer Leakage Inductance in concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current (im), especially at light load condition. The theoretical discussion relies on the asymmetry of the EI core by placing the secondary winding in a close contact with the magnetic core and placing the primary winding in the vicinity of the air gap. Moreover, noise absorber had been utilized to control the Leakage Inductance value. The proposed transformer design maximizes the value of the secondary Leakage Inductance and minimizes the primary Leakage Inductance. Alongside with the theoretical discussion, experimental tests had been conducted to evaluate the proposed method using a 390V-12V, 220W LLC resonant converter.
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effects of secondary Leakage Inductance on the llc resonant converter part ii frequency control bandwidth with respect to load variation
Applied Power Electronics Conference, 2019Co-Authors: Mostafa Noah, Tomohide Shirakawa, Kazuhiro Umetani, Jun Imaoka, Masayoshi Yamamoto, Eiji HirakiAbstract:Resonant converters rely on a precise knowledge of Leakage Inductance of the equipped transformers. Resonant circuit topologies such as LLC usually utilize the transformer Leakage as an inductive component in the resonant tank, allowing for a drastic reduction in the converter weight, size and volume. The existence of the secondary Leakage Inductance affects the whole operation of the LLC resonant converter. This paper reveals that placing the secondary winding near the air gap would increase the resonant tank input impedance, vertically shrink the voltage-gain curve of the converter, and consequently minimize the frequency range (i.e frequency bandwidth with respect to load variation). On contrary, placing the secondary winding in a close contact with the magnetic core would decrease the resonant tank input impedance, vertically stretches the voltage-gain curve of the converter, and widen the frequency variation range. It has been reported that the winding location with respect to the air gap has an impact on the Leakage Inductance value. In other words, placing the secondary winding in a close contact with the magnetic core (zero mmf position) would maximize the Leakage energy storage originated from the secondary winding, and hence maximize the secondary Leakage Inductance and vice versa. The theoretical discussion is presented which is merely based on Ampere’s law and Dowell’s model. Furthermore, transformer prototypes had been constructed and tested in a 390V/12V-220W LLC converter prototype to evaluate the proposed analysis.