Materials Science Forum Vol. 721

Abstract: In this paper, the impact of high wind power and photovoltaics penetration on the dynamic behavior of an island power system like one operates in Crete is investigated. Several simulations were performed leading to the fact that it is possible to achieve higher level of renewable energy sources penetration without significant dynamic security problems, if power units spinning reserve exists and the corresponding control systems have a sufficiently fast response.

Abstract: Energy harvesting is a key technology for small self-sufficient devices, which use environmental energy as a source. If these devices target a wireless sensor network, their required energy is only a few mW. In our previous report, we demonstrated the ability to harvest 6.32 mW from a magnetic field of 21.2 μT at 60 Hz. This paper considers an array module design for power line magnetic noise energy harvesting. The experimental results show that small distance in axial direction makes the harvesting energy small. In order to investigate this phenomenon, magnetic flux distributions around the modules are also measured. From the results, we concluded that the modules should be separated by one diameter distance of the coil.

Abstract: Microgrids integrating distributed motor-generator units are commonplace in locomotive and industrial applications. The behavior of these systems is dependent upon various design-operating parameters. However there is a distinct relation between power quality and power flow within these units. This paper presents an analysis of power quality measurements, depicting this interdependence. Respective results can be taken under consideration during power flow programming, enabling enhanced system operation.

Abstract: Behavior of suspended magnetic and nonmagnetic micrometer-size particles in a micro-tube filled with a magnetic fluid is investigated by using the discrete particle method based on the simplified Stokesian dynamics in order to know the polishing process of inner wall of a tube. It is shown that the chain-like clusters of magnetic particles are surrounded by clusters of nonmagnetic particles in the presence of uniform magnetic field. The clusters are held in the field direction in case of rotation of the micro-tube and in case of rotation of magnetic field.

Abstract: In-vessel tritium inventory in fusion reactors has to be reduced from a view point of safety in fusion reactors. It is required to evaluate the amount of tritium retained in tungsten plasma facing walls. The plasma discharge with hydrogen isotope (deuterium) was conducted to evaluate the tritium retention in tungsten. The glow discharges using helium, neon and argon were performed after the deuterium discharge to reduce the deuterium retention. The use of inert gas discharge little reduced the deuterium retention. Namely, the inert gas glow discharge is not useful to reduce the tritium inventory. The deuterium glow discharge significantly replaced the hydrogen in the tungsten wall into the deuterium. Thus, the deuterium glow discharge is quite useful to reduce the tritium inventory through the hydrogen isotope exchange. The use of neon or argon glow discharge followed by deuterium discharge can more reduce the tritium inventory. In addition, the tritium inventory can be easily reduced if the wall baking with a temperature of 700-800K is conducted.

Abstract: This paper presents distributions of the local vector magnetic properties in a three-phase induction motor model core measured with a new vector hysteresis sensor (V-H sensor). The exciting conditions used in the measurements were common sinusoidal and PWM excitation. The influence of the modulation frequency on vector magnetic properties is made clear.

Abstract: White layers, which often cause a break of a rail, are generated on its top surface when train wheels spin on it. Therefore its early detection of damaged conditions of the rail that may lead to a break is a critical activity in the rail maintenance. In this study, we have developed an effective method to detect the white layer on the top surface of the rail by using a Superconducting Quantum Interference Device (SQUID).

Abstract: In this paper, we present a frequency sweeping excitation and spectrogram method (FSES method) for non-destructive testing of hardened carbon steels. The FSES method can evaluate the electromagnetic properties in materials which were changed after induction heating. Therefore, it’s possible to evaluate the hardening conditions using the FSES method. We applied our method to the practical car seat parts to use in actual products. The surface of the hardening sample is deformation by the induction heating. We show the method that can evaluate the hardening conditions without being influenced by the surface deformation.

Abstract: Magnetic gears are a force transmitter consisting of permanent magnets. The mechanical input can be transmitted to an output shaft without contact by magnetic forces. The magnetic gears are not worn out because there is no friction. As a result, the running costs such as the maintenance fee can be suppressed and the resources can be saved. However, the transmission torques of the conventional magnetic gears, which have so far been developed, are very low. Besides, new structure models designed for high torque density need a lot of permanent magnets and multi-pole constructions. Those structures are complex and the manufacturing is difficult. In this research, we applied a flux concentration type surface permanent magnet arrangement to a surface permanent magnet type magnetic gear in order to improve the transmission torque and to reduce the amount of permanent magnets. The magnetic flux distribution, the gap flux density and the transmission torque of the developed new models are numerically analyzed by using the two-dimensional finite element method. In this paper, a permanent magnet structure optimized to reduce its amount and influence of the flux concentration type surface permanent magnet arrangement on the gap flux density distribution and transmission torque are reported.

Abstract: Equations for reconstructing 3D images of internal flaws are presented. Waveforms were measured from a simple reference sample to derive the response function of the probe, and the response function was calculated based on those waveforms. A sample with internal flaws was prepared to evaluate the reconstructed images of internal flaws derived by EMAT using magnetostrictives. 3D-images of an internal flaw could be derived using this response function.