Design und Entwicklung von MHz-Wechselrichtern für den Leistungsbereich über 10 kW

Im Rahmen dieser Arbeit wurden Möglichkeiten zur Realisierung von Hochfrequenzwechselrichtern mit Ausgangsleistungen über 10 kW bei 2,50 MHz untersucht. Hierzu wurden zwei Ansätze mit unterschiedlichen SiC-Transistoren betrachtet. Zum einen wurde ein Generator mit einer Ausgangsleistung von 25 kW realisiert. Dieser basierte auf speziell für diese Anwendung entworfenen Halbbrückenmodulen und es konnte einen maximale Effizienz von 94,9% erreicht werden. Alternativ wurde eine Kaskadenschaltung aus kompakten 2,5 kW-Generatoren aufgebaut. Dabei wurden die kleineren Generatoren aus Standardbauteilen aufgebaut und erreichten einzeln einen Effizienz von 93,9%. In der Kaskadenschaltung aus vier 2,5 kW-Generatoren konnte einen Gesamteffizienz von 92,7% erreicht werden

Compact and Highly Efficient 2.5 MHz SiC Electronic Ballast for Inductively Coupled UV Lamps

Inductively coupled UV lamps require a high-frequency alternating current for ignition and efficient operation. In this work, we present a switch-mode half-bridge inverter, with SiC-MOSFETs, which achieves a conversion efficiency from the DC-Link to a 2.5 MHz alternating current of 95% at 750W lamp power, including auxiliary power for the gate drivers and the controller. Furthermore, the paper describes an algorithm for the active power measurement of a 2.5 MHz voltage and current signal with an oscilloscope, averaging in the frequency domain and spectral distinction of the active power at the switching frequency

Inductive Medium Pressure UV-Source

Abstract: In this paper, an efficient inductively coupled medium pressure source for ultraviolet radiation (UV-source) is demonstrated. The lamp was operated with powers up to 3kW while the radiation and the coldest point temperature were measured. In addition, different coil geometries were investigated. Here a symmetrical and asymmetrical winding density were compared. Also the operation pressures and DC to radiation efficiencies are presented. In this work, an operation pressure of one atmosphere and an UV-efficiency (200–380 nm) of 15.5% was achieved. This is comparable to conventional medium pressure Hg-lamp technology. The main advantage of the presented inductive lamp is the electrodeless operation and therefore the longer service life, since an electrode failure is eliminated

Control of a SiC 2.5 MHz resonant full-bridge inverter for inductively driven plasma

The electronic ballast of an inductively driven plasma faces a mostly inductive, variable load impedance. The SiC full-bridge inverter uses the inductive behavior to achieve zero-voltage-switching and a switching frequency of 2.5 MHz, at 3.9 kVA and 764W in the plasma. The control is realized on a modern, small TI Piccolo microcontroller with a high-resolution PWM module and compensates for the variable load impedance. We present design and experimental results of a 2.5 MHz inverter for inductively driven plasma without the need for a large FPGA controller

Current Mode Control of a Series LC Converter Supporting Constant Current, Constant Voltage (CCCV)

This paper introduces a control algorithm for soft-switching series LC converters. The conventional voltage-to-voltage controller is split into a master and a slave controller. The master controller implements constant current, constant voltage (CCCV) control, required for demanding applications, for example, lithium battery charging or laboratory power supplies. It defines the set-current for the open-loop current slave controller, which generates the pulse width modulation (PWM) parameters. The power supply achieves fast large-signal responses, e.g., from 5 V to 24 V, where 95% of the target value is reached in less than 400 s. The design is evaluated extensively in simulation and on a prototype. A match between simulation and measurement is achieved

Assessing social, emotional, and intercultural competences of students and school staff. A systematic literature review

The inclusion of social, emotional, and intercultural competences (SEI) in academic contexts has been supported by international organizations, such as the European Union, the United Nations, and the OECD, since the early 2000s. However, little information is yet available regarding the assessment of these competences. This paper shares the findings of a systematic literature review that produced an inventory of existing tools for the assessment of SEI competences of students and school staff. This is the first time assessment tools for these three competences have been concurrently reviewed. An interdisciplinary and international research team conducted this systematic literature review in the databases of ERIC, PsycInfo, PSYNDEX, Scopus, and Web of Science. Out of 13,963 articles, 149 assessment tools were examined and processed. In addition to the instrument analysis and a detailed description of the procedure, this article shows the basic theoretical concepts, as well as the limitations, of such a review. It was found that 1) the majority of the discovered instruments rely on self-reported survey and inventory data, 2) of the three competences, intercultural competence had the fewest relevant instruments, and 3) very few tools have been created to assess all three competences together. From this review, it is apparent that a wider variety of assessment tools (other than self-reports), as well as more comprehensive tools (e.g. qualitative analysis of vignettes) for the assessment of all three SEI competences, should be developed to meet international demand. The results of the literature review are available and freely accessible in the form of an assessment catalogue. (DIPF/Orig.

Reducing the Transition Hysteresis of Inductive Plasmas by a Microwave Ignition Aid

Inductive plasma discharge has been a part of continuous investigations since it was discovered. Especially the E- to H-mode transition and the hysteresis behavior have been topics of research in the last few decades. In this paper, we demonstrate a way to reduce the hysteresis behavior by the usage of a microwave ignition system. With this system, a significant decrease of the needed coil current for the ignition of the inductive driven plasma is realized. For the microwave generation, a magnetron as in a conventional microwave oven is used, which offers a relatively inexpensive way for microwave ignition aid. At the measured pressure of 7.5 Pa, it was possible to reduce the needed coil current for the inductive mode transition by a factor of 3.75 compared to the mode transition current without the ignition aid. This was achieved by initiating the transition by a few seconds of microwave coupling. The performed simulations suggested that the factor can be further increased at higher pressures. That is especially interesting for plasmas that are hard to ignite or for RF-sources that cannot deliver high enough currents or frequencies for the ignition