Tasuku Takagi

Role of the metallic phase arc discharge on arc erosion in Ag contacts

The influence of the metallic-phase arc discharge on contact performance was studied for breaking Ag contacts. Measured parameters were whole arc duration (metallic-phase plus gaseous-phase arc duration), metallic-phase arc duration, contact resistance, bridge energy, and electrode material mass change. The tests were carried out under the various conditions of air pressure and contact current. The experimental results showed that the contact resistance increased when the arc duration in the metallic-phase arc region grew, and it was high and almost became constant when the arc reached the transition border to the gaseous phase. The material loss and transfer is log-proportional to the accumulated metallic-phase arc duration, irrespective of the air pressure condition. The effect of whole arc duration was not clear in the material mass change when the air pressure was varied. From many test results, it is concluded that the material mass change mainly depends on the metallic-phase arc rather than the whole arc duration. This means that the metallic-phase arc duration affects the material loss and transfer and the constant resistance, while the gaseous-phase arc has little influence. >

Distribution of Arc Duration and Material Wear Due to Arc for Ag, Cu, and Pd Contacts

An apparatus to measure the arc duration in moving contacts has been developed, which not only measures a breaking arc duration for each contact operation, but also integrates the durations of all arcs occurring during the contact operating period. The apparatus is applied to measure the distribution of arc duration and to find the relationship between material wear and integrated arc duration. Ag, Cu, and Pd are tested as basic contact materials. The results obtained in the experiments show that the arc duration distributions have some characteristics peculiar to the contact materials, and the relationship between the wear and the integrated arc duration is found for each contact material. Ag has an interesting character in both the distribution of arc duration and the wear.

Relationship between contact operating conditions and contact phenomena in Ag and Pd breaking contacts

A measuring system for electric contact phenomena is described from the viewpoint of simultaneous data acquisition such as arc duration, contact resistance, and material wear, (transfer) under specific operating conditions, in order to find the relationship between contact operating conditions and contact parameters. The system and results from its use are discussed. Contact materials tested are Ag and Pd. The focus is on parallel data acquisition, which is feasible for some, but not all, parameters. Parallel data acquisition resulted in some novel discoveries, which are discussed.<<ETX>>

Effects of ferrite sheet attachment to portable telephone in reducing electromagnetic absorption in human head

In order to reduce the spatial peak specific absorption rate (SAR) in a human head due to a portable telephone, we have proposed attaching a ferrite sheet to the portable telephone. In this paper, the mechanism of SAR reduction is reviewed and then the effects of the attachment location and size, and the material properties of ferrite sheet on the SAR reduction are investigated by using the finite-difference time-domain (FDTD) method in conjunction with a detailed human head model. Their effects on the antenna radiation efficiency are also given. The results lead to a guide to choosing and designing a ferrite sheet with the maximum SAR reducing effect for portable telephones.

A cyclic charge-balancing A/D converter with capacitor mismatch error compensation

An algorithm is proposed for improving the speed of a charge-balancing analog-to-digital converter implemented by a switched-capacitor technique. The number of charge transfer operations required for a conversion is reduced. For example, the conversion rate in 16-b conversion is improved more than 128 times as compared to a conventional charge-balancing analog-to-digital converter. A compensation algorithm for the capacitor mismatch error is also proposed. The results of prototype experiments indicate that the maximum integral nonlinearity error is reduced to less than 0.04 LSB in 6-b conversion. >

Relationship between Bridge Energy and Metallic Phase Arc Duration in Electric Contacts

In order to find the relationship between arc duration, contact resistance and bridge energy in electric contacts, a new system for measuring bridge waveforms has been developed. The bridge energy was controlled by heating the contact electrode. The experimental results showed that the arc duration of opening contact is closely related to the bridge energy supplied to its bridge state. This fact suggests that the amount of metallic vapor (initial condition) plays an important role in maintaining the metallic phase arc discharge.

Development of a high-speed time-resolved spectroscope and its application to analysis of time-varying optical spectra

The authors have developed a spectroscopic measuring system that is controlled by a microcomputer to analyze a time-varying optical spectrum. A charge-coupled-device (CCD) linear image sensor, which has 128 pixels is used as an optical detector, so that the optical spectrum can be measured quickly in a parallel way. The spectrum to be measured ranges from about 350 to 700 nm in wavelength. All data are digitized and transferred to a microcomputer for storage on a floppy disk, and they can be processed for display in various forms. This system has been applied to the spectrum analysis of light emitted due to a contact arc discharge.

Two-stage computational cost reduction algorithm based on Mahalanobis distance approximations

For many pattern recognition methods, high recognition accuracy is obtained at very high expense of computational cost. In this paper, a new algorithm that reduces the computational cost for calculating discriminant function is proposed. This algorithm consists of two stages which are feature vector. Division and dimensional reduction. The processing of feature division is based on characteristic of covariance matrix. The dimensional reduction in the second stage is done by an approximation of the Mahalanobis distance. Compared with the well-known dimensional reduction method of K-L expansion, experimental results show the proposed algorithm not only reduces the computational cost but also improves the recognition accuracy.

A New Method for the Measurement and Integration of Arc Durations in Electrical Contacts

A unique method for the continuous measurement of electric-arc duration is presented. By using the method, it is possible to know the distribution of arc durations at any instance of time and, at the same time, the integration of arc durations has become much more convenient and less time consuming than any other existing methods. It has also been found that the total integrated-arc durations bear a linear relationship with the number of operations on a log-log scale.

Variation of Arc Duration of Electric Contacts Due to Controllable Atmospheric Condition

A new measuring system Of contact phenomena has been developed, which can control noncorrosive atmospheric conditions such as air pressure, mixture of air and noncorrosive gas, and electrode temperature. The developed system is controlled by a microcomputer and measured quantities can be processed also by the microcomputer, and the final data can be printed Out and/or displayed. Arc duration and contact resistance can be measured under several atmospheric conditions at fixed contact opening speed. Contact materials of Ag and Pd were tested, and many interesting results for variation of arc duration have been obtained. For example, the variation of the arc duration for Ag and Pd contacts has a different tendency from each other with respect to the atmospheric pressure, and the variation of the arc duration relates the contact resistance.