Materials Science Forum Vol. 721

Abstract: The magnetic gears can transmit torque without contact by applying magnetic force. So in comparison to normal mechanical gears, it may offer a lot of advantages such as low noise, low vibration, wear less, dustless and no lubricant oil at all. Besides, when a very large of input torque entered, magnetic force that pull each other exceeds it limit and the gear spin empty, resulting these magnetic gears limited the torque transmission and can function as torque limiter. However, as disadvantage, it is lack in transmitting torque. In the previous research, we designed cylindrical magnetic gear prototype to increase torque transmission and measured slip torque only. As a torque transmitter, the measurement of driving torque itself is more important. Therefore, the purpose of this research is to measure and study the driving torque due to implication of revolution speed, distance between the magnetic gears and rotational load.

Abstract: This paper describes an analysis of torque characteristics of a noncontact spinning system using linearly actuated magnets. This noncontact spinning system spins the suspended object (here is an iron ball) without contact by the remanent magnetization and the linear movement of four permanent magnets. In this paper, the remanent magnetization point is modeled, and the rotational torque of this mechanism is calculated by IEM (Integral Element Method) analysis. The rotational torque is also measured using a measurement device with strain gauges. According to the IEM analysis results and the experimental results, the rotational torque characteristics of the noncontact spinning system are discussed.

Abstract: It was experimentally shown that joint application of a solar station and a superconducting flywheel (a kinetic energy storage device) can solve the main problem of renewable energy sources: to provide uninterrupted and controlled power supplying. The storage device changes its operation mode (stand-by, charging, discharging) practically without any delay and its use leads to an increase of the transient stability of a power system.

Abstract: The importance of distribution transformer no-load loss on the operation of modern electrical grids is often underestimated. Internationally, distribution transformer no-load loss constitutes nearly 25% of the transmission and distribution losses of electrical grids. The losses in European Union distribution transformers are estimated at about 33 TWh/year whereas, reactive power and harmonic losses add a further 5 TWh/year. In the Greek electrical grid the no-load losses of 140,000 distribution transformers are estimated at about 490 GWh/year. This paper has two goals the first one is to illustrate the significance of distribution transformer no-load loss in periods of high electric energy cost and the second goal is the presentation of a novel numerical methodology for wound core transformers no-load loss analysis, enabling to determine the economically and technically optimum transformer for every use.

Abstract: The paper presents a possibility of supplying the electromagnetic vibrators with variable frequency voltage. Two types of modulated controls of the inverter’s commutation angle are presented. The theoretical analysis allows the study of the variable element influence on the distortion factor and of the harmonic content generated by the vibrator. The authors present an experimental validation of the presented theory, using the harmonic measurement of the distorted waveform. The harmonic response is useful in quantifying the performances of the harmonic filters to be introduced between the nonlinear consumer and the power grid and on the other hand the electromagnetic interference determined to other customers connected to the power grid.

Abstract: Several operation principles and generator types have been developed because of the growing interest for the wave energy conversion systems (WECSs). A WECS is demanded to be more efficient so that the overview of the already developed systems is necessary. An overview of the different operation principles and the various linear generator types is presented analyzing the advantages and the disadvantages. Finally, a complete scheme gathering the most vital characteristics is introduced.

Abstract: This paper evaluates the current status of renewable energy sources integration and future trends, especially of the photovoltaics, in the interconnected power system of Greece and the power system of Crete Island, which is the largest isolated power system in Greece. Focusing on the ongoing developments and prospects, the paper investigates the impacts of the expected sufficient photovoltaic installations on the energy market and the greenhouse gas emissions, as well as the reduction in CO2 emissions costs due to the installation of photovoltaics and other renewable energy technologies.

Abstract: The paper presents a coupled electrical aerodynamic model for a three blade wind-turbine dynamic analysis. The model is based on a blade element representation of the aerodynamic load part combined with an aeroelastic beam element for the dynamic analysis of a real rotor blade, including top tower acceleration. The model involves reduced computation time enabling to be applied in control system hardware. Such an analysis is very promising for obtaining controllers involving compromises among contradictory targets such as energy capture maximization and mechanical stresses reduction in the aerodynamic part.

Abstract: In the paper a Preisach hysteresis model is applied to determine the dynamic behavior of a steel column with a mass on the top and loaded by periodically alternating force. The column is considered as a completely rigid element, while the fixed end of the column is modeled with a rotational spring with hysteresis characteristic. In the solution of the non-linear dynamical equation of the motion the fix-point technique is inserted to the time marching iteration. The cycling time of the force is changing. The results are plotted in figures.

Abstract: The development of code for finite elements-based field computation has been going on at a pace since the 1970s, yielding code that was not put through the software lifecycle – where code is developed through a sequential process of requirements elicitation from the user/client to design, analysis, implementation and testing and release and maintenance. As a result, today we have legacy code running into millions of lines, implemented without planning and not using proper state-of-the-art software design tools. It is necessary to redo this code to exploit new object oriented facilities and make corrections or run on the web with Java. Object oriented code’s principal advantage is reusability. Recent advances in software make such reverse engineering/re-engineering of this code into object oriented form possible. The purpose of this paper is to show how existing finite element code can be reverse/re-engineered to improve it. Taking sections of working finite element code, especially matrix computation for equation solution as examples, we put it through reverse engineering to arrive at the effective UML design by which development was done and then translate it to Java. This then is the starting point for analyzing the design and improving it without having to throw away any of the old code. Using auto-translators and then visually rewriting parts by the design so revealed, has no match in terms of speed and efficiency of re-engineering legacy code.