Effects of external stress on magnetic properties in motor cores

The effects of shrink fitting on the magnetic properties of iron cores are investigated in order to simulate the magnetic behavior of iron cores mounted in motor frames. Shrink fittings, of course, decrease permeability and increase effective magnetostriction and magnetic loss. It is well known that the magnetostriction increment and the permeability decrement are explained by the increase of magnetoelastic energy due to compressive stress by shrink fitting. The magnetic loss increases, however, cannot be explained by this energy. We demonstrate experimentally that the magnetic loss increases result from mechanical work due to the magnetostrictive movement of the iron core under compressive stress. © 1998 Scripta Technica, Electr Eng Jpn, 123(1): 15–22, 1998     

Evaluation of compensation ratios in a power assist system based on operational sensation

This paper deals with topics relating to a power assist system that is used for attenuating load force. In such systems, it is a serious problem that maneuverability and stability are lost when the actuators are saturated. To avoid this problem, we have proposed a power assist system with individual compensation ratios for gravity and dynamic load. In this paper, based on the operational sensation, we confirm the validity of the proposed method and discuss how the compensation ratios should be determined through our experiments.     

Space change behavior in full scale ±250 kV dc XLPE cables

Space charge in full size ±250 kV dc cables was measured using a pulse-electroacoustic method. Two newly developed types of dc XLPE cables with 20 mm thick insulation were subjected to measurements at a dc voltage of 500 kV, keeping the conductor temperature either at room temperature or at 85°C. Qualitative analyses of the space charge distribution and the quantitative analysis of the electric fields in the vicinity of semicon interfaces were made. It was shown that the field in the vicinity of the inner semiconductor tends to increase by 10 to 40% when the polarity of the applied voltage was switched, in the case when the conductor was kept at 85°C. However, the distortion of the electric field was significantly smaller than that expected with conventional XLPE cables. As a result, dc cables are considered to have stable dc characteristics from the viewpoint of space charge behavior. © 1998 Scripta Technica, Electr Eng Jpn, 124(2): 16–28, 1998     

Time-scaling control of an underactuated manipulator

Position control of an underactuated manipulator that has one passive joint is investigated. The dynamic constraint caused by the passive joint is second-order nonholonomic. Time scaling of the active joint trajectory and bidirectional motion planning from the initial and the desired configurations provide an exact solution of the positioning trajectory. The active and passive joints can be positioned to the desired angles simultaneously by swinging the active joints only twice. Feedback control constrains the manipulator along the planned path in the configuration space. Simulation and experimental results show the validity of the proposed methods. © 1998 John Wiley & Sons, Inc.     

Concept and Performance of a Non-Azide Propellant for Automotive Airbag Inflators

A university laboratory and three companies have collaborated to develop a non-azide propellant for automotive airbag inflators which is composed of azodicarbonamide(ADCA), potassium perchlorate(KClO₄), and additives such as burning catalyst, binder and others. The new propellant aims at low cost, small size of inflators, featuring low toxicity of not only raw materials of the propellant but also effluent gases, particulates and residues generated on deployment of an airbag. No hygroscopicity and low hazard of the propellant will make manufacturing, transportation, and handling easy. The performances of the propellant were evaluated by strand test, pressure chamber test, 7.5 l tank test, 60 l tank test, and airbag deployment test. The strength of the pellet of the new propellant was evaluated by a small ball drop test.     

A current sensor using the Faraday effect in optical fiber manufactured from flint glass

For application to current monitoring in electric power facilities, the authors have been developing a current sensor utilizing the Faraday effect of an optical fiber manufactured from flint glass having a very small stress-optic coefficient. This paper describes the result of study on constructing the sensing system, which is composed of a sensor head, a light source, fibers for light transmission and a signal processing circuit. First, results from investigation are reported with respect to causes affecting performance and durability of the sensor, and examinations of countermeasures also are described. As a result of the research, it was confirmed experimentally that several means are effective to improve characteristics of the sensor. Then, design and test results of a sensor model constructed with application of the means are described. From the test results it was proved that the model shows excellent characteristics satisfying basic requirements of the standard for conventional current transformers. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (3): 22–38, 1997     

A new method for system optimization by neural networks

This paper proposes a new method of optimizing the operation of a power transmission system, based on a structured neural network. Because the structured neural network is built by prewiring, the network construction time is very short. Simulations of transmission loss of reduction have been carried out. It is shown that the optimization performance of the proposed method is satisfactory in practice. © 1997 Scripta Technica, Inc. Electr Eng Jpn. 118 (4): 27–34, 1997     

Development of metallic substrate supported planar solid oxide fuel cells fabricated by atmospheric plasma spraying

A planar solid oxide fuel cell (SOFC) consisting of a cell supported with a porous metallic substrate and a metallic separator has been developed. In the fabrication of the cell, anodes and electrolytes were formed on sintered Ni-felt substrates using flame spraying (FS) and atmospheric plasma spraying (APS), respectively. The APS is also applied to form (LaSr)MnO₃ protective coatings on the metallic separators. With these metallic cells and separators, a 3 kW-class stack, which consisted of 30 cells (15-cell block×2) was constructed and operated. The active electrode area of the cell was 600 cm². The stack generated 3.3 kW at 970 °C when the current density was 0.3 Acm⁻² and the fuel utilization 50%. It did not show any degradation for the initial 2100 h, but a few cells in the lower 15-cell block became unstable after 2100 h. On the other hand, the upper 15-cell block was stably operated for 3200 h.     

Elucidation of accuracy in calibration of MR signal intensity based on transmission amplitude method

To calibrate magnetic resonance (MR) signal intensity that depends on radio frequency (RF) coil loading, the transmission amplitude (TRA) for the excitation in the transmit-receive RF coil has been used as a good index in the so-called TRA method. As this TRA method needs neither an internal reference nor an additional external reference for the calibration, its accuracy is free from reference measurements. This study elucidated the calibration accuracy of MR signal intensities based on the TRA method. A cylindrical gel phantom was used for accuracy measurements with a 1.5-T MRI unit with conventional TI imaging as a simple pulse sequence for various loading conditions. The brain parenchyma of eight healthy volunteers also showed calibrated MR signal deviations. The error of the phantom calibration measurements was 2.18% (S.D.%). The background noise intensity of images was theoretically derived to correlate with the impedance mismatching of the RF coil, which is inevitable for fixed tuning, even for automatic tuning that is not always exact. Taking into account this noise intensity, the calibration method was modified to reduce its error to 1.50%. The standard deviations of the calibrated values in the thalamus and frontal white matter were 2.9 and 3.8%. respectively. We suggest that the modified TRA method is a practical and reliable technique to obtain clinical numeric evidence.     

Studies on oil distribution in polymer blends

Oils and resins are widely used in rubber industries to improve or control the mechanical properties, viscoelastic behavior, processability, and tackiness of a rubber compound. Very few fundamental studies have been reported on the function and the mechanism of oils and resins in a rubber mixture. In this article oil or resin distribution to each phase in an immiscible binary elastomer blend was studied by measuring the change of thermodynamical parameters, such as glass transition temperature, melting point of crystallines, and heat at melt of each polymer component. Several independent approaches give consistent results. It was found that aromatic oil was favorably distributed to the polystyrene-butadiene (SBR) phase of an SBR/natural rubber (NR) blend. Similarly, unequal distribution of resin in a blend was observed for a natural resin (rosin) and a petroleum resin. © 1996 John Wiley & Sons, Inc.