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.

Optimal Level Number and Performance Evaluation of Si/GaN Multi-Level Flying Capacitor Inverter for Variable Speed Drive Systems

Abstract: This paper analyzes the optimal number of voltage levels concerning power density for a motor-integrated Multi-Level Flying Capacitor inverter (ML FCi) with 800 V DC-link driving a 7.5 kW Permanent Magnet Synchronous Motor (PMSM). The analysis is performed for an ML FCi, as it enables high efficiency and power density required for motor integration on the one hand and decreases the output filter volume with increasing output voltage level numbers N on the other hand. General scaling laws of the ML FCi are derived analytically and a Pareto optimization based on real hardware dimensions is performed to determine which number of levels is optimal in terms of power density and efficiency and which system performance is achieved for employing Si or GaN power transistors.

Wireless Power Supply of Moving Linear Actuator Enclosed in Stainless-Steel

Abstract: Linear actuators are a key element of automatized industrial systems, as linear motion is present in most manipulation tasks. For actuators performing x-z movements, actuator windings are placed on the moving part and these must be supplied. However, in high-purity environments such as in the food processing or pharmaceutical industries, actuators should be fully enclosed in stainless steel (SS) to facilitate thorough cleaning, and cables are undesirable. This paper therefore proposes high-efficiency (97% at 100W) wireless power transfer (WPT) through two 0.5mm thick SS enclosures, which facilitates the deployment of linear actuators in high-purity environments. The proposed coaxial transformer arrangement with the magnetic core mounted on the moving part results in a magnetic field that is in parallel to the SS enclosures, which minimizes eddy-current losses. We discuss the detailed modeling and optimization of the system, and finally present an industrial two-axis actuator prototype that fully confirms the theoretical analysis.

Control circuit for electronically operated switch applicable on power semiconductor, has auxiliary supply terminal, diode and condenser for supply of driving circuit

Abstract: The control circuit has an auxiliary supply terminal (21), a diode (22) and a condenser (23) for supply of a driving circuit (17), where a connection of the condenser is attached at supply input of the driving circuit and another connection of the condenser is attached at another supply input of the driving circuit The former connection of the condenser is attached over a serial switching of the diode and the auxiliary supply terminal is attached at the former connection of the switch (12)

Vorschaltgerät für eine gasentladungslampe

Abstract: Ein Vorschaltgerat fur eine Gasentladungslampe (2) enthalt im Lastkreis (1) eine Drossel und in einer Treiberschaltung (11) fur einen Inverter (7) mit hochohmigen Schalterelementen (8) einen Transformator (14). Zur Verminderung des Schaltungsaufwands sollen die Primarwicklung Tp und die Sekundarwicklung Ts des Transformators (14) einen gemeinsamen Kern (16) haben.

Experimental Efficiency Evaluation of Stacked Transistor Half-Bridge Topologies in 14 nm CMOS Technology

Abstract: Different Half-Bridge (HB) converter topologies for an Integrated Voltage Regulator (IVR), which serves as a microprocessor application, were evaluated. The HB circuits were implemented with Stacked Transistors (HBSTs) in a cutting-edge 14 nm CMOS technology node in order to enable the integration on the microprocessor die. Compared to a conventional realization of the HBST, it was found that the Active Neutral-Point Clamped (ANPC) HBST topology with Independent Clamp Switches (ICSs) not only ensured balanced blocking voltages across the series-connected transistors, but also featured a more robust operation and achieved higher efficiencies at high output currents. The IVR achieved a maximum efficiency of 85.3% at an output current of 300 mA and a switching frequency of 50 MHz. At the maximum measured output current of 780 mA, the efficiency was 83.1%. The active part of the IVR (power switches, gate-drivers, and level shifters) realized a high maximum current density of 24.7 A/mm2.

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.