A review of stator fault monitoring techniques of induction motors

Condition monitoring of induction motors is a fast emerging technology for online detection of incipient faults. It avoids unexpected failure of a critical system. Approximately 30-40% of faults of induction motors are stator faults. This work presents a comprehensive review of various stator faults, their causes, detection parameters/techniques, and latest trends in the condition monitoring technology. It is aimed at providing a broad perspective on the status of stator fault monitoring to researchers and application engineers using induction motors. A list of 183 research publications on the subject is appended for quick reference.     

Aggregation of the scarab beetleHolotrichia consanguinea in response to female-released pheromone suggests secondary function hypothesis for semiochemical

The pheromone system of the scarab beetleH. consanguinea, an agricultural pest native to India, was investigated by extracting abdominal glands of females with dichloromethane and ether and analyzing them by GC-MS. Indoor bioassays with the natural product separated on a silica gel column showed that males responded to the hexane-ether (80:20) fraction by displaying a clear sexual behavior. Although the indoor bioassay-oriented approach did not lead to the identification of the active compound(s), field tests of candidate chemicals—anisole, indole, and phenol—showed that beetles responded strongly to anisole. Males and females were captured in anisolebaited traps in a ratio close to 1:1. Nearly the same sex ratio was also observed in beetles captured over the time during the flight activity of the beetles in the field. Because no clear evolutionary basis exists for why competing females are attracted to the semiochemical, it was simply referred to as a “female-released pheromone.”     

Donor-like localization and activated conduction in compensatedn-Hg0.8Cd0.2Te

We report first results on the activated resistivity inn- type Hg_0.8Cd_0.2Te crystals heavily compensated through native acceptor defects (double acceptor mercury vacancies). Three activation energies are reported, all of which increase with increasing compensation. In conjunction with the variation of Hall coefficient and Hall mobility with temperature we conclude, i) formation of (donor⁺-acceptor⁻) pairs during stoichiometric annealing, ii) distortion of second acceptor states of the paired mercury vacancies to raise them near, or in the conduction band, and iii) the pair states, when occupied with electrons in the presence of excess unpaired donors, behave like localized donors, and when unoccupied, like electron traps and/or recombination centres.     

Experimental Investigation on Electrical Discharge Drilling of Ti-6Al-4V Alloy

This article describes the experimental investigation related to creation of holes in aerospace titanium alloy workpiece using static electrode machining and electrical discharge drilling (EDD) process. Special attachment for holding and rotating the tool electrode was developed and installed on electrical discharge machining (EDM) machine by replacing the original conventional tool holder provided on die sinking EDM. The effect of input parameters such as gap current, pulse on-time, duty factor and RPM of tool electrode on output parameters for average hole circularity (C_a) and average surface roughness (R_a) have been studied. It is observed that the effect of rotating electrode machining has considerable influence on the output parameters over stationary electrode machining. The micro-graphs and photographs of few selected samples were taken by SEM and metallurgical microscope, which also commensurate with the findings of the study.     

Development and Experimental Study of Milling Electrochemical Spark Micromachining (M-ECSMM) of Silicon

Silicon - Milling Electrochemical Spark Micromachining (M-ECSMM) is hybrid micromachining process which is used to create microfeatures in non-conducting materials. Silicon is one of the abundantly...     

Sub-zero Temperature Dependence of Tensile Response of Friction Stir Welded Al-Cu-Li (AA2198) Alloy

Mechanical properties at ambient and cryogenic temperatures of Al-Cu-Li alloy are required for design and fabrication of liquid hydrogen and liquid oxygen tanks of satellite launch vehicles. In the present work, bead-on-sheet, friction stir welding was carried out with three different rotation speeds. The yield and strain hardening behaviors of the welds were evaluated in temperature range of 20 K to 298 K. Both yield stress and strain hardening ability in the specimen increased with decrease in testing temperature. The dependence of yield stress on temperature was modeled on the basis of thermally activated dislocation mobility, while that of strain hardening was modeled on the temperature dependence of dynamic recovery rate parameter. The recovery parameter followed an Arrhenius-type relationship with temperature. The model parameters determined from the experimental data were further used to simulate the stress–strain curves at different sub-zero temperatures for the friction stir welds.

     

Effect of Cu and Li Contents on the Serrated Flow Behavior of Al-Cu-Li Based Alloys

Metallurgical and Materials Transactions A - The serrated flow behavior of Al-Li, Al-Cu and Al-Cu-Li alloys was studied in solution-treated condition under a range of strain rates at ambient...