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.

Single-Phase Full-Wave Rectifier as an Effective Example to Teach Normalization, Conduction Modes, and Circuit Analysis Methods

Abstract: Application of a single phase rectifier as an example in teaching circuit modeling, normalization, operating modes of nonlinear circuits, and circuit analysis methods is proposed. The rectifier supplied from a voltage source by an inductive impedance is analyzed in the discontinuous as well as in the continuous conduction mode. Completely analytical solution for the continuous conduction mode is derived. Appropriate numer- ical methods are proposed to obtain the circuit waveforms in both of the operating modes, and to compute the performance parameters. Source code of the program that performs such computation is provided.

Double Stator Linear-Rotary Actuator with a Single Set of Mover Magnets

Abstract: Double stator (DS) linear-rotary actuators (LiRAs) are mainly used in machining applications with high force and torque demands, such as milling or turning. The mover of a typical DS LiRA contains two sets of permanent magnets, one arranged as in radial-flux rotating machines and the other as in tubular linear machines. A back iron is sandwiched between these two sets of permanent magnets, rendering the mover heavy and bulky. Consequently, DS LiRAs are not suitable for applications with high dynamics, such as pick-and-place robots in the packaging and semiconductor industries. In order to increase the dynamics of DS LiRAs, two different ironless mover layouts are proposed in this work. The achievable forces and torques are calculated using finite element method (FEM) simulations and compared to the standard DS LiRA. Manufacturing limitations of the proposed mover layouts and their influence on the performance are considered. Moreover, cogging force and cogging torque of the standard and proposed LiRAs are compared. To verify the FEM models used in the analysis, a simplified test setup with a flat mover is presented. The flux linkage is measured and a good agreement with FEM simulations is demonstrated.

Electrical converter and control method

Abstract: An electrical converter (10) comprises an input voltage selector (12) for converting a three-phase AC input voltage provided at three phase inputs (a, b, c) of the electrical converter into an intermediate three-phase voltage provided at an upper voltage node (x), a middle voltage node (y) and a lower voltage node (z); capacitors (C x , C y , C z ) interconnecting an upper voltage node (x), a middle voltage node (y) and a lower voltage node (z); and an output converter (14) for converting the intermediate three-phase voltage into an output voltage; wherein the input voltage selector (12) is adapted for connecting the upper voltage node (x) to a phase input (a, b, c) with the highest voltage of the three-phase AC input voltage, the lower voltage node (z) to a phase input (a, b, c) with the lowest voltage of the three-phase AC input voltage, and the middle voltage node (y) to the phase input (a, b, c) having a voltage between the highest voltage and the lowest voltage.

Active Gate Control for Current Balancing in Paralleled IGBT Modules in a Solid State Modulator

Abstract: Summary form only given. In the paper an active gate control for paralleled IGBTs in a solid state modulator is presented. There, the focus is put on the rising and falling edges and the overshoot which are very important for klystron applications. For controlling the current sharing and providing fast switching also a high dynamic gate drive is presented in the paper. There, a PCB integrated Rogowski current probe is used which has a high bandwidth and enables a low inductive construction required for the pulse modulator.

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.