Verification and expansion of a method of transient analysis of voltage collapse based on the induction motor load model

Voltage instability is now under intensive study in Japan, and some dynamic methods for analyzing voltage collapse have already been presented. However, the suitability of load models used in the methods and the generality of the results have not been verified. In this paper, useful voltage collapse data acquired in real power systems are presented. The measured data are compared with the result of dynamic digital simulation to verify the suitability of an induction motor load model. In the latter half of this paper, dynamic simulations of voltage collapse with consideration of generator dynamics are carried out. An interconnected power model system with 10 nodes is analyzed. The generality of basic characteristics concerning voltage collapse which have already been obtained without considering generator dynamics is verified by such simulations.     

Measurement of leak current generation distribution in PEFC and its application to load fluctuation testing under low humidification

A study was performed to establish a method for measuring the position and amount of leak current increase during operation of a fuel cell. This measurement method was applied to load fluctuation testing at low humidification and the increase in the leak current was observed in the downstream zone of the cell. The tested cell was disassembled and cross sections were observed under the SEM. The SEM images revealed the formation of a Pt band near the cathode catalyst in the downstream zone of the cell. This may be the cause of the degradation of the membrane at the downstream. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 1–9, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21038     

Alloy Casting by the Horizontal Ohno Continuous Casting System

Abstract

Sn-Pb alloys in the compositional range 2.5–22.5% Pb have been continuously cast using the horizontal Ohno Continuous Casting (OCC) process. The effects of alloy composition and process variables on the location and size of the liquid-solid zone were investigated and information obtained was examined in order to establish the breakout point. It was found that the liquid-solid zone existed partly or entirely within the mould during casting, depending on casting conditions. The liquid-solid zone expanded with increasing mould-cooler distance and also with decreasing mould exit temperature, whereas it remained constant with the casting speed within the range investigated. As the composition approaches the eutectic point, the L+S zone shifted into the mould, and existed entirely within the mould at 22.5% Pb. It was also found that breakout occurred when the rod temperature at the mould exit exceeded a critical temperature which can be expressed as Tc=228–2A, where Tc is the critical rod temperature in Celsius and A is wt% Pb (<22.5% Pb). It was confirmed that the mould exit temperature must be kept above the liquidus temperature of the alloy to be cast in order to obtained unidirectional or single crystal materials.     

Copolymerization of styrene with acrylamide in an emulsifier-free aqueous medium

Copolymerization of styrene with acrylamide was carried out in an emulsifier-free aqueous medium. The resulting latex contained an appreciable amount of acrylamide-rich copolymer in the serum. The copolymerization course was divided into three stages on the basis of the main reaction locus. At first, acrylamide polymerized in preference to styrene in the aqueous phase. Water-soluble growing radicals lost hydrophilicity rapidly and nucleated the particles. After particle formation, styrene polymerized exclusively in the particles until styrene droplets disappeared. The decrease in the concentration of residual styrene monomer caused growing radicals to keep the hydrophilicity for a long time, and polymerization of acrylamide was accelerated in the aqueous phase. Polymerizations at higher temperature and lower pH resulted in prolongation of the first stage of the polymerization, that is, preferential polymerization of acrylamide in the aqueous phase. An increase in the acrylamide fraction in monomer feed caused some decreases in the particle size and its uniformity.     

Wear of some F.C.C. metals during unlubricated sliding part IV: Effects of atmospheric pressure on wear

The dependence of wear on atmospheric pressure was studied in relation to the fatigue of materials. Ni, Cu and Au specimens were fatigued at various atmospheric pressures and the results were compared with their wear behaviours. Similar curves were obtained for each material when the reciprocal of the fatigue life and the number of wear fragments were plotted against the atmospheric pressure. It was concluded that changes in the number of wear fragments or in the amount of wear are governed by the resistance of the materials to fatigue. On the basis of the findings obtained, mechanisms of wear are discussed.     

Continuous measurement of dynamic tensile mechanical properties in polymer solids over a wide range of frequencies. I. An instrument with driving force of 15 kgwt and frequency range 10−3–102Hz

Two compact apparatuses were designed and fabricated for the study of dynamic mechanical viscoelastic behavior in polymer solids over a wide range of frequencies: (1) 10^?3–10² Hz with a tensile driving force of 15 kgwt, and (2) 10–10⁴ Hz with a maximum tensile driving force of 15 kgwt. The present paper reports the details of the instrument of (1). The instrument contains a nonresonant and forced vibration system, where the rectilinear vibration is taken from the rotating shaft of the driving motor through the double eccentric crank and conrod-slider machineries. Measurements can be conducted at any desirable frequency (10^?3-10² Hz) and displacement (0–2 mm). Subjected to longitudinal vibration, the stress and strain in the specimen are detected by a compression-type load cell and noncontacting displacement meter, respectively. The specimen clamp was especially devised for the compression-type load cell, which enables direct conversion from the tensile force on the specimen to the compressive force against the load cell without any medium. Another feature of the instrument is a vertical combination of vibrational driving system, specimen clamp, and load cell. These are important for the effective transmission of the driving force to the specimen and avoidance of unnecessay mechanical vibration noises. From the Lissajous' figure formed with two signals of the stress and strain, the values of dynamic tensile modulus and loss factor for polymeric materials are easily obtained.