Browsing by Author "Sehirli, E."

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Design and numerical analysis of thermal capability of power transformer using coupled electromagnetic field-thermal model
(Springer Science and Business Media Deutschland GmbH, 2024) Cetinceviz, Y.; Sehirli, E.
In this study, by using the co-simulation technique, the dry-type transformer is designed for a wind turbine with 3.8 MVA, 690 V/36 kV power, and voltages. Dry-type transformers used in wind turbines require extra effort at the design stage concerning oil-immersed type because of the limited cooling capacity of air, possible higher inrush currents, resonant overvoltage, higher voltage, and load fluctuations that degrade thermal behavior. Furthermore, transformer design and analysis of their thermal behavior cannot be realized through one simulation software. Therefore, another approach using different simulation software simultaneously is needed, called co-simulation or multi-physics solution. This paper investigates transformer design and its effect on the system using a co-simulation technique including ANSYS Maxwell 3D, Simplorer, and Mechanical. After realizing the three-dimensional transformer design, its lumped parameter consisting of inductance matrix, leakage inductances, and resistances are determined analytically and using an eddy current solver. Core losses of the transformer, high- and low-voltage windings voltages, and their harmonic spectrums under different load conditions, including ohmic and inductive loads, are defined, the steady-state thermal solution is performed, and conclusions are made. It is proved that the transformer design works as desired.
Design and numerical analysis of thermal capability of power transformer using coupled electromagnetic field-thermal model
(2024.01.01) Cetinceviz, Y.; Sehirli, E.
In this study, by using the co-simulation technique, the dry-type transformer is designed for a wind turbine with 3.8 MVA, 690 V/36 kV power, and voltages. Dry-type transformers used in wind turbines require extra effort at the design stage concerning oil-immersed type because of the limited cooling capacity of air, possible higher inrush currents, resonant overvoltage, higher voltage, and load fluctuations that degrade thermal behavior. Furthermore, transformer design and analysis of their thermal behavior cannot be realized through one simulation software. Therefore, another approach using different simulation software simultaneously is needed, called co-simulation or multi-physics solution. This paper investigates transformer design and its effect on the system using a co-simulation technique including ANSYS Maxwell 3D, Simplorer, and Mechanical. After realizing the three-dimensional transformer design, its lumped parameter consisting of inductance matrix, leakage inductances, and resistances are determined analytically and using an eddy current solver. Core losses of the transformer, high- and low-voltage windings voltages, and their harmonic spectrums under different load conditions, including ohmic and inductive loads, are defined, the steady-state thermal solution is performed, and conclusions are made. It is proved that the transformer design works as desired.
Examining the Design of Different Types of DM EMI Filters and Their Effect on EMI Noise and Control Characteristics for Cuk DC-DC Converter
(2023.01.01) Sehirli, E.
In this paper, DM EMI filters including LC, LC with damping, and Pi and LCL filters are designed for DC-DC Cuk converter operated in BCM. Although, DM EMI is so important for any power converter, the effect of DM filter is not investigated in detail in literature with respect to control characteristics and DM noise reduction. The main contribution of this paper is comparisons of DM EMI filter topologies regarding control characteristics and EMI noise reduction which is not presented in the literature. Another contribution is to give a practical design methodology for EMI filter design avoiding complex mathematical procedures. Besides, the paper designs an LCL filter, popular for inverter applications, for Cuk converter that is not introduced in the literature. Examining the filter effect on the converter from the control point of view is a very complicated issue because a linearized model of the converter which is naturally nonlinear should be obtained. To do so, the converter's small signal analysis must be derived. Therefore, for examining the effect of filters, a small signal analysis of the Cuk converter is made through an average state-space model. After that, transfer functions of each filter topology are obtained. Lastly, the entire transfer functions of the system using both the Cuk converter and each filter are acquired, separately. By using the transfer functions of overall systems, the effect of each filter topology is investigated by root locus and bode plots. Moreover, experimental verification of all filters is realized over a 15W Cuk converter with a 25kHz switching frequency. It is validated by applications that the LCL filter provides better control characteristics on the Cuk converter, the total inductor value is reduced by 30% and the total capacitor value is reduced by 25% compared to other filters. However, with respect to DM noise Pi and LC filters give better results.
Investigation of the Effect of Different Electromagnetic Interference Filter Topologies to DC-DC Boost Converter for Continuous Conduction Mode
(2024.01.01) Sehirli, E.
This paper presents the design and application of boost converter operated in continuous conduction mode for 15 W, with 25 kHz switching frequency with induc tor-capacitor-inductor (LCL), pi, inductor capacitor (LC) with damping, and LC electromagnetic interference filters. Also, modeling and analysis of the boost converter in terms of state space and small signal are given. Furthermore, the effect of each filter to differential mode (DM) noise and to control characteristics by root locus and bode diagrams for the boost converter are presented, which is not presented in detail in the literature for the boost converter. All results obtained by applications and simulations are compared. Moreover, frequency spectrums are given to compare DM noises. As a result, for control point of view, LCL filter provides better results, and for reducing DM noise, the LC and pi filters are superior to others. Besides, the LCL filter reduces the inductor value by 30% compared to other filters.
Modeling, Analysis, and Winding Loss Calculation of Different Litz and Solid Wire on Coupled Inductor in DC-DC Cuk Converter for DCM
(2024.01.01) Sehirli, E.; Cetinceviz, Y.
In this article, the coupled inductor is designed using a litz wire, an enameled litz wire, and a solid wire separately. All the coupled inductors wound with litz and solid wires are tested in a Cuk converter operated in DCM with a 25 kHz switching frequency for 15 W power, and winding losses of each wire, including proximity and skin effect loss, are calculated analytically without using any software, by using different techniques presented in literature, and the results are compared. Also, state-space modeling of the converter using a coupled inductor for DCM is derived as a contribution of the article because such a modeling is not derived for the Cuk converter in the literature. Thanks to the applications, inductor currents, switch voltage, input-output voltage, and output current are measured for coupled inductors with different wires. In addition, FEM simulation and co-simulation of all coupled inductors are realized, and the results obtained by applications are verified by them. Besides, it is shown that while the number of turns is the same, increasing the bundle of wires increases efficiency and inductance, reducing the window area and coupling coefficient.