Johann W. Kolar

Bio: Johann W. Kolar is an academic researcher from ETH Zurich. The author has contributed to research in topics: Rectifier & Three-phase. The author has an hindex of 97, co-authored 965 publications receiving 36902 citations. Previous affiliations of Johann W. Kolar include Alstom & Infineon Technologies.

Multiple cell power conversion method and multiple cell power converter

Abstract: PROBLEM TO BE SOLVED: To provide a multiple cell power conversion method and multiple cell power converter.SOLUTION: A power converter circuit includes a power converter having a plurality of conversion cells connected in series. Each of the plurality of conversion cells includes at least one first half-bridge circuit including a first silicon MOSFET (metal oxide semiconductor field effect transistor) and a second silicon MOSFET. At least one of the plurality of conversion cells is configured to be operated in a continuous current mode.SELECTED DRAWING: Figure 1

Transient Behavior of Solid-State Modulators With

Abstract: Solid-state modulators based on pulse transformers offer the advantage that, with the turns ratio of the transformer, the primary voltage could ideally be adapted to available switch technology, and a series connection of switches could be avoided. To increase the power level, several semiconductor switches must be connected in parallel, and a balancing between the differ- ent switches must be guaranteed. Here, the matrix transformer concept, which is based on multiple primary and/or secondary windings, as well as flux adding, offers superior performance with respect to the achievable rise times. However, the influence of the parasitic elements on the voltage and current distribution is quite involved. In this paper, the influence of the parasitic elements of the matrix transformer on the current balancing and on the winding voltages is investigated based on reluctance models. Additionally, the inherent current balancing of the matrix transformer for windings mounted on different cores is explained. Furthermore, the influence of parasitic load/transformer capacitances on the turnoff transient is discussed in detail.

Design and Characterization of a Bearingless Cross-Flow Fan

Abstract: This paper presents a high-speed bearingless cross-flow fan particularly suited for applications in chemically demanding environments. In general, bearingless motors convince with a friction-and wear-free operation, unlimited lifetime and a hermetically-sealed encapsulation of the rotor. For the proposed cross-flow fan, a double-sided use of such motors additionally leads to twice the available torque for the blade rotation as well as a highly compact and safe system design. In sophisticated applications (e.g. gas-circulation systems of excimer laser) those arguments are crucial. After a description of the motor topolopy, the novel bearingless cross-flow fan prototype is introduced. To characterize its performance, measurements are performed on a ISO 5801 based test rig.

Verfahren zum Regeln eines Dreiphasen-Pulsgleichrichtersystems mit Stromzwischenkreis.

Abstract: Die Erfindung betrifft ein Verfahren zum Regeln eines Dreiphasen-Pulsgleichrichtersystems (1, 2, 3) mit einer Dreiphasen-Bruckenschaltung (2), einer Zwischenkreisinduktivitat (L), und einem Lastkonverter (3). In zeitlich aufeinanderfolgenden Abschnitten wird jeweils in einem Abschnitt folgendes ausgefuhrt: • In jenem Bruckenzweig, im folgenden ausgewahlter Bruckenzweig genannt, der Dreiphasen-Bruckenschaltung (2), welchem die Netzphase mit dem betragsmassig grossten Phasenstrom, im Folgenden ausgewahlte Netzphase genannt, zugeordnet ist, wird diese Netzphase wahlweise in Abhangigkeit der Polaritat des Phasenstromes mit einem Schalter des ausgewahlten Bruckenzweigs, im Folgenden ausgewahlter Schalter genannt, einem positiven Anschlusspunkt (p) oder einem negativen Anschlusspunkt (n) der Dreiphasen-Bruckenschaltung (2) verbunden, wobei diese Netzphase bei positivem Phasenstrom mit dem positiven und bei negativem Phasenstrom mit dem negativen Anschlusspunkt verbunden wird, und wahrend der Dauer dieses Abschnitts verbunden bliebt. • In den anderen beiden, nicht ausgewahlten Bruckenzweigen wird durch Taktung der dem ausgewahlten Schalter gegenuberliegenden Schalter der entsprechende positive respektive negative Anschlusspunkt wechselweise mit den beiden nicht ausgewahlten Phasen verbunden. Ferner betrifft die Erfindung eine Vorrichtung zum Regeln eines Dreiphasen-Pulsgleichrichtersystems (1, 2, 3).

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Multilevel inverters: a survey of topologies, controls, and applications

Abstract: Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

Recent Advances and Industrial Applications of Multilevel Converters

Abstract: Multilevel converters have been under research and development for more than three decades and have found successful industrial application. However, this is still a technology under development, and many new contributions and new commercial topologies have been reported in the last few years. The aim of this paper is to group and review these recent contributions, in order to establish the current state of the art and trends of the technology, to provide readers with a comprehensive and insightful review of where multilevel converter technology stands and is heading. This paper first presents a brief overview of well-established multilevel converters strongly oriented to their current state in industrial applications to then center the discussion on the new converters that have made their way into the industry. In addition, new promising topologies are discussed. Recent advances made in modulation and control of multilevel converters are also addressed. A great part of this paper is devoted to show nontraditional applications powered by multilevel converters and how multilevel converters are becoming an enabling technology in many industrial sectors. Finally, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.