621 Angewandte Physik
Refine
Document Type
- Conference proceeding (35)
- Book chapter (3)
- Patent / Standard / Guidelines (3)
- Journal article (2)
Is part of the Bibliography
- yes (43)
Institute
- Technik (43) (remove)
Publisher
- IEEE (16)
- Hochschule Ulm (6)
- VDE Verlag (3)
- Hanser (2)
- Technische Universität Darmstadt (2)
- British Institute of Non-Destructive Testing (1)
- Elsevier (1)
- GRID-FTN (1)
- Hochschule Reutlingen (1)
- Public Verlagsgesellschaft und Anzeigenagentur (1)
Condition Monitoring for mechanical systems like bearings or transmissions is often done by analysing frequency spectra obtained from accelerometers mounted to the components under observation. Although this approach gives a high amount on information about the system behaviour, the interpretation of the resulting spectra requires expert knowledge, that is, a deep understanding of the effect on condition deterioration on the measured spectra. However, an increasing number of condition monitoring applications demands other representations of the measured signals that can be easily interpreted even by non–experts. Therefore, the objective of this paper is to develop an approach for processing measured process data in order to obtain an easy to interpret measure for assessing the component condition. The main idea is to evaluate the deterioration of a component condition by computing the correlation function of current measurements with past measurements in order to detect a component condition deterioration from a change in these correlation functions. Besides the simplicity of the obtained measure, this approach opens the opportunity for integrating a model based approach as well. The developed method is tested based on a condition monitoring application in a roller chain.
This work presents a spiral antenna array, which can be used in the V- and W-Band. An array equipped with Dolph-Chebychev coefficients is investigated to address issues related to the low gain and side lobe level of the radiating structure. The challenges encountered in this achievement are to provide an antenna that is not only good matched but also presents an appreciable effective bandwidth at the frequency bands of interest. Its radiation properties including the effective bandwidth and the gain are analyzed for the W-Band.
The superior electrical and thermal properties of silicon carbide (SiC) allow further shrinking of the active area of future power semiconductor devices. A lower boundary of the die size can be obtained from the thermal impedance required to withstand the high power dissipation during a short-circuit event. However, this implies that the power distribution is homogeneous and that no current filamentation has to be considered. Therefore, this work investigates this assumption by evaluating the stability of a SiC-MOSFET over a wide range of operation conditions by measurements up to destruction, thermal simulations, and high-temperature characterization.
This paper addresses the turn-on switching process of insulated-gate bipolar transistor (IGBT) modules with anti-parallel free-wheeling diodes (FWD) used in inductive load switching power applications. An increase in efficiency, i.e. decrease in switching losses, calls for a fast switching process of the IGBT, but this commonly implies high values of the reverse-recovery current overshoot. To overcome this undesired behaviour, a solution was proposed which achieves an independent control of the collector current slope and peak reverse recovery current by applying a gate current that is briefly turned negative during the turn-on process. The feasibility of this approach has already been shown, however, a sophisticated control method is required for applying it in applications with varying currents, temperature and device parameters. In this paper a solution based on an adaptive, iterative closed-loop ontrol is proposed. Its effectiveness is demonstrated by experimental results from a 1200 V/200A IGBT power module for different load currents and reverse-recovery current overshoots.
Induced by a societal decision to phase out conventional energy production - the so-called Energiewende (energy transition) - the rise of distributed generation acts as a game changer within the German energy market. The share of electricity produced from renewable resources increased to 31,6% in 2015 (UBA, 2016) with a targeted share of renewable resources in the electricity mix of 55%-60% in 2035 (RAP, 2015), opening perspectives for new products and services. Moreover, the rapidly increasing degree of digitization enables innovative and disruptive business models in niches at the grid's edge that might be the winners of the future. It also stimulates the market entry of newcomers and competitors from other sectors, such as IT or telecommunication, challenging the incumbent utilities. For example, virtual and decentral market places for energy are emerging; a trend that is likely to speed up considerably by blockchain technology, if the regulatory environment is adjusted accordingly. Consequently, the energy business is turned upside down, with customers now being at the wheel. For instance, more than one-third of the renewable production capacities are owned by private persons (Trendsearch, 2013). Therefore, the objective of this chapter is to examine private energy consumer and prosumer segments and their needs to derive business models for the various decentralized energy technologies and services. Subsequently, success factors for dealing with the changing market environment and consequences of the potentially disruptive developments for the market structure are evaluated.
Die vorliegende Erfindung betrifft ein Transmission Line Pulssystem zum Erzeugen eines elektrischen Pulses, sowie ein diesbezügliches Verfahren. Dabei umfasst das Transmission Line Pulssystem: eine Transmission Line, eine Energieversorgungsquelle zum Aufladen der Transmission Line und einen Entladungsschalter zum Auslösen einer Entladung der aufgeladenen Transmission Line, dadurch gekennzeichnet, dass die Transmission Line eine Vielzahl von Einzelsegmenten umfasst, wobei jedes Einzelsegment über ein zugehöriges Einstellglied mit einem gemeinsamen Massepotential elektrisch verbunden ist, und wobei zumindest eines der Einstellglieder einen Einstellkondensator und einen Einstellschalter aufweist.
Die vorliegende Erfindung betrifft eine Schaltungsanordnung mit einer Bootstrap-Schaltung, die zumindest eine Hauptkapazität aufweist, von der die erste Seite mit einem ersten Zweig der Schaltungsanordnung und die zweite Seite mit einem auf veränderlichem Potential liegenden zweiten Zweig der Schaltungsanordnung verbunden ist. Die vorgeschlagene Schaltungsanordnung zeichnet sich dadurch aus, dass die Bootstrap-Schaltung parallel zur Hauptkapazität wenigstens eine weitere Kapazität aufweist, die über eine zweite Versorgungsspannung auf eine höhere Spannung aufladbar ist als die Hauptkapazität und über wenigstens ein Schaltelement zur Unterstützung der Hauptkapazität zuschaltbar ist. Bei der vorgeschlagenen Schaltungsanordnung kann in Abhängigkeit von der Dimensionierung der Bootstrap-Kapazitäten eine sehr viel kleinere Fläche mit höherem oder gleich bleibenden Spannungseinbruch oder eine nicht so starke Flächenreduzierung mit kleinerem Spannungseinbruch verglichen mit einer herkömmlichen Bootstrap-Schaltung erzielt werden.
Virtual prototyping of integrated mixed-signal smart sensor systems requires high-performance co-simulation of analog frontend circuitry with complex digital controller hardware and embedded real-time software. We use SystemC/TLM 2.0 in conjunction with a cycle-count accurate temporal decoupling approach (TD) to simulate digital components and firmware code execution at high speed while preserving clock-cycle accuracy and, thus, real-time behavior at time quantum boundaries. Optimal time quanta ensuring real-time capability can be calculated and set automatically during simulation if the simulation engine has access to exact timing information about upcoming inter-process communication events. These methods fail in the case of non-deterministic, asynchronous events, resulting in potentially invalid simulation results. In this paper, we propose an extension to the case of asynchronous events generated by blackbox sources from which a priori event timing information is not available, such as coupled analog simulators or hardware in the loop. Additional event processing latency or rollback effort caused by temporal decoupling is minimized by calculating optimal time quanta dynamically in a SystemC model using a linear prediction scheme. We analyze the theoretical performance of the presented predictive temporal decoupling approach (PTD) by deriving a cost model that expresses the expected simulation effort in terms of key parameters such as time quantum size and CPU time per simulation cycle. For an exemplary smart-sensor system model, we show that quasi-periodic events that trigger activities in TD processes are handled accurately after the predictor has settled.
The paper illustrates the status quo of a research project for the development of a control system enabling CHP units for a demand-oriented electricity production by an intelligent management of the heat storage tank. Thereby the focus of the project is twofold. One is the compensation of the fluctuating power production by the renewable energies solar and wind. Secondly, a reduction of the load on the power grid is intended by better matching local electricity demand and production.
In detail, the general control strategy is outlined, the method utilized for forecasting heat and electricity demand is illustrated as well as a correlation method for the temperature distribution in the heat storage tank based on a Sigmoid function is proposed. Moreover, the simulation model for verification and optimization of the control system and the two field test sites for implementing and testing the system are introduced.
The current paper discusses the optimal choice of a filter time constant for filtering the steady state flux reference in an energy efficient control strategy for changing load torques. It is shown that by appropriately choosing the filter time constant as a fraction of the rotor time constant the instantaneous power losses after a load torque step can be significantly reduced compared to the standard case. The analysis for the appropriate choice of the filter time constant is based on a numerical study for three different induction motors with different rated powers.