Design of 100kVA Ultra-High Efficiency Pole Transformer by Improving Eddy Current Losses Kim, Sang-Hyun Department of Electrical Engineering Graduate School of Soongsil University

                                     3-4 Estrutura do núcleo do transformador

 Design of 100kVA Ultra-High Efficiency Pole Transformer by Improving Eddy Current Losses Kim, Sang-Hyun Department of Electrical Engineering Graduate School of Soongsil University

ABSTRACT

In Korea, electricity demand is increasing due to industrial development and economic growth. Due to the increase in power demand, transmission and distribution losses are also increasing. The transmission and distribution loss rate in Korea is 3.6% of the total electric energy, of which about 2% is caused by losses in distribution transformers. Power transformers with high capacity and voltage have already achieved high efficiency through many studies. However, Pole transformers with low capacity and voltage are in fact lacking research on high efficiency despite the fact that about 2.2 million units are installed nationwide. The purpose of this paper is to design the ultra-high efficiency pole transformer that changes the core and winding materials and it - xii - reduces the eddy current loss of the winding and other structures for the 100kVA high efficiency pole transformer. In order to analyze the advanced technology, we analyzed overseas 100kVA high efficiency pole transformer and examined the technologies necessary for product development. In addition, The eddy current loss of low voltage windings and high voltage windings was calculated using a finite element method, and the eddy current loss was reduced by changing the shape of conductor, winding arrangement, and insulating paper. In order to reduce the eddy current loss of other structures, the loss was reduced either by inserting a nonmagnetic material between the low voltage bushing terminals or by changing the shape and material of the clamp. Finally, The iron core and winding materials of transformers were designed by using an amorphous core and copper conductor to maximize efficiency, and the 100kVA ultra-high efficiency pole transformer was designed by improving the eddy current loss of the windings and other structures. In order to verify the design, a transformer with the same specifications as the design model was manufactured to validate the effect, and compared with a high efficiency pole transformer, an efficiency of 99.56%(50% load) with an efficiency increase of 0.29% was developed. The eddy current loss reduction studies presented in this paper are expected to be used as data necessary for the development of transformers with other capacities. The final developed 100kVA ultra-high efficiency pole transformer is expected to contribute to improving the efficiency of the domestic distribution system

LINK ORIGINAL: http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=87c33062fa1d9da7ffe0bdc3ef48d419

LINK: http://www.mediafire.com/file/5z8z65z43a031c9/Design_of_100kVA_Ultra-High_efficiency.pdf/file

Toroidal Transformer Design Optimization for The Application of High-Frequency Power Converters BY Himanshu-Department of Electrical and Computer Engineering The Graduate School Pusan National University-2019

Toroidal Transformer Design Optimization for The Application of High-Frequency Power Converters BY Himanshu-Department of Electrical and Computer Engineering

The Graduate School Pusan National University-2019

Dissertation for the degree of Doctor of Philosophy

Abstract

The high-frequency-based inverter is used in renewable energy power sources for power transmission. However, power quality is compromised as a result of the increase in common mode noise currents by the high inter-winding parasitic capacitance in high-frequency link transformers. This fast voltage transient response leads to harmonic distortion and transformer overheating, which causes power supply failure or many other electrical hazards. This paper presents a comparative study between conventional and modified toroid transformer designs for isolated power supply. A half bridge high-frequency (10 kHz) small power DC–AC Voltage inverter was designed along with power source; a 680 W solar module renewable system was built. An FEM-simulation with Matlab-FFT analysis was used to determine the core flux distribution and to calculate the total harmonics distortion (THD). A GWInstek LCR meter and Fluke VT04A measured the inter-winding capacitance and temperature in all four transformer prototypes, respectively. The modified design of a toroid ferrite core transformer offers more resistance to temperature increase without the use of any cooling agent or external circuitry, while reducing the parasitic capacitance by 87%. Experiments were conducted along with a mathematical derivation of the inter-winding capacitance to confirm the validity of the approach.

LINK ORIGINAL:http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=79b3a1cb6ca326e0ffe0bdc3ef48d419

LINK:https://www.mediafire.com/file/7o3knzbx43lgenw/Toroidal_Transformer_Design_Optimization.pdf/file

NEWS, WEBINAR Las Nuevas Pautas Para la Educación en Ingeniería en Brasil -16 de Junio a las 11 AM EDT-Prof. Dr. Jose Roberto Cardoso

¿Cómo un país con 210 millones de habitantes, la octava economía más grande del mundo, que alberga compañías como Petrobrás, Embraer, Vale y tiene una de las agroindustrias más grandes del planeta, logró poner la ingeniería en crisis?

¿Qué sucede cuando un contingente de casi 1,5 millones de inscripciones en cursos de ingeniería se reduce, en solo dos años, al 60% de este contingente y, al mismo tiempo, el número de cursos nuevos casi se duplica en el mismo período?

Razones como la dificultad del curso, el costo de la matrícula, la crisis en la economía, no son suficientes para justificar esta crisis sin precedentes, en comparación con ejemplos de otros países que han pasado por situaciones similares y surgieron gracias a la promoción de la ingeniería.

Todos estos puntos serán discutidos en este seminario web, para presentar, no solo las herramientas que el gobierno, la academia y las empresas están utilizando para mitigar este problema, sino también los grandes desafíos que se enfrentan para ganar esta batalla.

Presentador : Prof. Dr. Jose Roberto Cardoso

Graduado en Ingeniería Eléctrica por la Escola Politécnica da Universidade de São Paulo (1974) y doctorado en 1986. Fue Profesor Visitante en el Grenoble-INP-Francia. Es profesor en la Universidade de São Paulo desde 1999, coordinador del Laboratorio LMAG de Electromagnetismo Aplicado y GLIP – Global Institut for Peace de la USP. Fue director de EPUSP de 2010 a 2014. Fue el fundador de SBMAG-Sociedade Brasileira de Eletromagnetismo. Profesor Cardoso fue galardonado en 2013 con el título de Ingeniero Emérito del Año por el Instituto de Ingeniería de São Paulo y con el título de Doctor Honoris Causa por Grenoble-INP en 2019.

REGISTRE-SE NA SEGUINTE PAGINA WEB:

http://www.ifees.net/las-nuevas-pautas-para-la-educacion-en-ingenieria-en-brasil/

Modeling and Design of Medium-Frequency Transformers for Future Medium-Voltage Power Electronics Interfaces DOCTOR OF SCIENCES of ETH ZURICH presented by THOMAS PAUL HENRI GUILLOD

Modeling and Design of Medium-Frequency Transformers for Future Medium-Voltage Power Electronics Interfaces DOCTOR OF SCIENCES of ETH ZURICH (Dr. sc. ETH Zurich) presented by THOMAS PAUL HENRI GUILLOD MSc ETH

Abstract

Newly available fast-switching Medium-Voltage (MV) Silicon-Carbide (SiC) semiconductors are setting new limits for the design space of MV converters. Unprecedented blocking voltages (up to 15 kV), higher switching frequencies (up to 200 kHz), higher commutation speeds (up to 100 kVμs), and high temperature operation can be reached. These semiconductors feature reduced switching and conduction losses and, therefore, allow for the realization of extremely efficient and compact MV converters. Moreover, the increased blocking voltage allows the usage of simple single-cell topologies for MV converters instead of complex multi-cell systems. Hence, the MV SiC semiconductors are interesting for many applications such as locomotive traction chains, datacenter power supply chains, collecting grids for renewable energies, high power electric vehicle chargers, and more-electric aircraft. Most of these applications require an isolated DC-DC converter for providing voltage scaling and galvanic isolation. However, the increased voltages and frequencies allowed by MV SiC semiconductors create new challenges for the design of Medium-Frequency (MF) transformers, which start to become the bottleneck of isolated DC-DC converters in terms of power density and efficiency. More specifically, the winding losses (due to skin and proximity effects) and the core losses (due to eddy currents and hysteresis) are rapidly increasing and mitigate the advantages (e.g., the reduced volt-second product applied to the magnetic core) obtained with the increased operating frequencies. Moreover, the MV/MF PWM voltages with fast switching transitions are also particularly critical for the insulation of MF transformers and can lead to additional losses, thermal breakdowns, and partial discharge induced breakdowns. Finally, the MF transformers of DC-DC converters should feature reduced losses (efficiencies above 99:5 %) in order to match the performance offered by the MV SiC semiconductors. The main focus of this thesis is, thus, set on the design of highly efficient MV/MF transformers employed in isolated DC-DC converters. First, a theoretical analysis of MF transformers is conducted in order to extract the fundamental performance limitations of such devices. The nature of the optimal designs is examined with analytical models, scaling laws, and numerical optimizations. Afterwards, several points are identified as critical and are studied in more detail. First, the impact of model uncertainties and parameter tolerances on MF transformers is examined with statistical methods in order to highlight the achievable modeling accuracy. Then, a 2.5D numerical field simulation method is presented for assessing the impact of non-idealities on the losses produced by litz wire windings (e.g., twisting scheme and pitch length). Afterwards, the impact of MV/MF PWM voltages with fast switching transitions on the insulation is examined. The electric field pattern is analyzed inside, at the surface, and outside the insulation and shielding methods are proposed. Finally, the dielectric loss mechanisms of dry-type insulation materials under PWM voltages is examined in detail. Different analytical expressions are proposed for extracting the insulation losses and it is found that the dielectric losses can be significant for MV/MF transformers operated with MV SiC semiconductors. Design guidelines are proposed for the selection of appropriate insulation materials for MV/MF applications and silicone elastomer is identified as an interesting choice. All the presented results are verified with measurements conducted on different MF transformer prototypes. The derived models and results are applied to a MV isolated DC-DC converter, which is part of a MV AC (3:8 kV, phase-to-neutral RMS voltage) to LV DC (400 V) Solid-State Transformer (SST) demonstrator. This SST is aimed to supply future datacenters directly from the MV grid. The considered 25 kW DC-DC converter operates between a 7 kV DC bus and a 400 V DC bus. The usage of 10 kV SiC MOSFETs allows for the realization of the converter with a single-cell DC-DC Series-Resonant Converter (SRC). The DC-DC SRC is operated at 48 kHz as a DC Transformer (DCX) and the modulation scheme, which allows for Zero-Voltage Switching (ZVS) of all semiconductors, is examined in detail. The realized MV/MF transformer prototype features a power density of 7.4 kW/l (121 kWin3, 4.0 kW/kg, and 1.8 kW/lb) and achieves a full-load efficiency of 99:65 %. The complete DC-DC converter achieves an efficiency of 99:0 % between 50 % and 100 % load with a power density of 3.8 kW/l (62W/in3, 2.9 kW/kg, and 1.3 kW/lb). The results obtained with the constructed DC-DC converter, which are significantly beyond the stateof- the-art, demonstrate that MV/MF transformers can utilize the possibilities offered by the new MV SiC semiconductors.

LINK: https://www.research-collection.ethz.ch/handle/20.500.11850/353785

Novel Hybrid Unidirectional Three-Phase AC-DC Converter Systems by KAZUAKI MINO-Swiss Federal Institute of Technology (ETH) Zurich

Novel Hybrid Unidirectional Three-Phase AC-DC Converter Systems by KAZUAKI MINO A dissertation submitted to Swiss Federal Institute of Technology (ETH) Zurich EIDGENÖSSISCHE TECHNISCHE HOCHSCHULE ZÜRICH for the degree of Doctor of Sciences Presented by Kazuaki Mino E.E., M.Sc., Tokyo Denki University born December 23, 1968 citizen of Japan Accepted Accepted on the recommendation of Prof. Dr. J. W. Kolar, Examiner Prof. H. Akagi, Co-Examiner

Abstract

In order to reduce harmonics, many rectifier topologies have been developing. Passive rectifiers, which employ only passive components, e.g. phase shifting transformers, diode bridges, and inductors etc., show some advantages concerning high efficiency, low EMC, low complexity, and high reliability. The passive components could be compact if mains frequency is high as in aircraft and micro gas turbine applications. However, the output voltage is unregulated. Furthermore, the input current of the passive rectifiers results in a staircase waveform which is not high quality if compared to active rectifiers. In this thesis, the drawbacks of the passive rectifiers are reduced. A diode bridge rectifier whose harmonics are reduced by adding an inductor to a diode bridge is widely used in motor drive applications. Mains current quality of the diode bridge rectifier is improved if a large inductance of the passive inductor is employed. However, the inductor is bulky, heavy and occupies a large space. In this thesis, the power density of the diode bridge rectifier is improved. The Electronic Smoothing Inductor, which is able to control a current to a constant value, is applied to the diode bridge output to act as a passive inductor. A control scheme for the DC-link voltage and active damping control for filter resonances are proposed. Moreover, the filtering concept is established to effectively attenuate EMI emission. The system dimensioning of the rectifier system is also introduced. A 5kW prototype shows a significant improvement in power density. The behaviours of the proposed rectifier system are tested by assuming practical conditions, e.g. not only ideal but also unbalanced and distorted input conditions. The dynamic behaviours are also evaluated. From the results, it is verified that the Electronic Smoothing Inductor has a similar characteristic to a passive inductor having a large inductance. Therefore, the proposed rectifier system brings a significant improvement in power density without impairing any features of a diode bridge rectifier. On the other hand, the passive 12-pulse rectifier can be extended to a hybrid rectifier having two active switches operated in an interleaved manner. The proposed topology ensures a controlled output voltage. Furthermore, modulation schemes to realize a purely sinusoidal input current are proposed. A 10kW prototype has been build with respect to future more-electric aircraft applications. The design procedure including the magnetic components and the active parts is introduced in this thesis. The proposed hybrid rectifier and the control schemes are verified by numerical simulations and experimental results. The output voltage is regulated. Furthermore, the input current is improved from a 12-pulse staircase shape to sinusoidal by the proposed triangular modulation. Moreover, the proposed closed loop control of input currents is performed to track a reference independently of mains voltages e.g. unbalanced and distorted input voltages. Therefore, both output voltage regulation and improvement of input current quality for the 12-pulse rectifier have been achieved by the proposed schemes. This thesis presents two rectifier systems which perform successfully. Both systems are hybrid and allow output power to flow without switching behaviours. Therefore, the proposed rectifier systems have not only high quality characteristics but also a high reliability. The system configurations, control schemes and their features are introduced. 

LINK http://www.mediafire.com/file/0tokqbgz47ukn4e/eth-144-02.pdf/file