Silver contacts are separated at constant speed and break arcs are generated in a 300V-450V DC and 10A resistive circuit. The transverse magnetic field of a permanent magnet is applied to the break arcs. Motion of the break arcs, arc duration and the number of reignitions are investigated when side surfaces of the contacts are covered with insulator pipes. Following results are shown. The motion of the break arcs and the arc duration when the anode is covered with the pipe are the same as those without pipes. When the cathode is covered with the pipe, the motion of break arcs change from that without the pipes and reignitions occur more frequently. The arc duration becomes longer than that without the pipes because of the occurrence of reignitions. The number of reignition increases with increasing the supply voltage in 300V-400V. The period of occurrence of the reignition with pipes is shorter than that when the cathode is covered with the pipe.

In this paper, a contactless measurement technique of passive intermodulation (PIM) using a coaxial tube excited with standing waves is proposed. The principle of the proposed method is described using a two-port network model with the lumped resistances representing the losses of a specimen and test equipment. To show its validity, a test using nickel wires producing high PIM is carried out, and its PIM-dependency on DUT-position in the coaxial tube is simulated using the FDTD method. The simulated result shows a good agreement to the experiment. Through the examination, it is found that the power consumption by the PIM source in a specimen is essential in PIM production, and sensitive PIM detection does not require good matching condition. Finally, the relation between PIM-source size and generated PIM level is also examined. The result shows that at least 18 dB-PIM reduction is obtained by PIM source size in a half-wavelength conductive wire.

VI time responses of a conventional electromagnetic relay during breaking contact operations were measured. In a conventional switching circuit, unstable contact resistance, irregular bouncing, and poor reproducibility were confirmed. Using a transient current switch circuit and two sharpened contact electrodes, bouncing during a breaking operation was suppressed, and unstable contact resistance changes and reproducibility of breaking operation were also improved.

In recent years, there has been increasing demand to miniaturize wiring harness connectors in automobiles due to the increasing volume of electronic equipment and the reduction of the installation space allocated for the electronic equipment in automobiles for the comfort of the passengers. With this demand, contact failure caused by the fretting corrosion is expected to become a serious problem. In this report, we examined micro-structural observations of fretting contacts of two different tin plating thicknesses using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) and so on. Based on the results, we compared the microstructure difference of fretting contact caused by the difference of the tin plating thickness.

We propose a new electric contact device that greatly improves arc discharge characteristics. Electric contact functions are divided into an energizing operation and a switching operation. A capacitor is connected in series to a contact for switching contact. Using two conventional relay contacts, no arc operation is confirmed for a 42 V/3 A break operation. Contact resistances are measured over many operations, and the surfaces of electrodes are observed. A chip capacitor is arranged at one side of the contact electrodes of a twin relay, confirming the possibility of miniaturization.

A LiNbO3 piezoelectric actuator controls the Au-Au contact gap. The control accuracy of the actuator is within the sub-micron range. Contact voltage, contact current, displacement of electrodes and driving voltage of the actuator were continuously and synchronously recorded by an A/D converter and send to a computer. The measured oscillograph data for 1500 contact operation were processed by the computer. Factors of discharge and bridge phenomena were derived at a contact operation. The delay time between displacement and driving signal of the actuator increased when one side of electric contact were vibrated. The resonance was seen in the actuator, and the dependency to the current and the amplitude was seen.

Peculiar patterns of SiO2 contamination around the periphery of the contact trace caused by silicone vapor under switching at the boundary of 1.6 W were confirmed. For micro relays, the electrical power conditions are restricted to lower level. Therefore, it is important to ascertain the upper limit of the electrical power conditions for normal operation. The peculiar pattern is important as it is recognized as the first stage of the origination of contact failure. Causes of this pattern were discussed from the viewpoints of temperature distribution in the contact trace, molten metallic bridge, micro arc discharge, and supply of silicone vapor with oxygen. It is proposed that during the closing contacts, as maximum Joule heating occurs at the periphery of the true contact area and silicone vapor with oxygen is easily supplied at the periphery, SiO2 grows around the contact trace. For the opening contacts, as the bridge or micro arc appears, silicone vapor with oxygen is supplied only outside of the contacts. Thus SiO2 is formed mainly around the periphery of the trace. Moreover, SiO2 was scattered radially depending on the sputtering of molten metal under rupture of the bridge. Therefore, the peculiar pattern forms as a result.

The distributions of a spectral intensity of the breaking arc between silver contacts in DC 45-66 V/2.5-5.0 A circuits have been measured using a high-speed color video. As a result, a cathode brightening spot, which has a high spectral intensity, exists near the cathode surface. The cathode brightening spot expands with the increase of the contact gap, but its length expands until about 18µm. When the contact gap spreads over about 180 µm, a dark positive column appears and grows between the cathode brightening spot and the anode surface. The higher the interrupted current is, the larger the diameter of the cathode brightening spot will be. The maximum diameter of cathode brightening spot is 500 µm under these experiments.

The authors observed the correlation between electromagnetic noise and trace of discharge on surface for various surface areas of Cu in opening copper (Cu)-carbon (C) electrodes. In the case of Cu (anode)-C (cathode), the duration of sporadic burst noise generated by discharge becomes longer when Cu surface area is increased, and trace of discharge (melting area) distribute widely on electrodes. Also the forms of the burst noise in the start of arc are classified, and the traces of discharge correspond to each forms. The forms of the burst noise depend on the pattern which the trace of discharge are formed. As these results, the authors showed the correlation between form of burst noise and trace of discharge on electrode surface.

We discussed on relationship between the width of slit ray and the accuracy of the measurement system for surface profile of electric contact. To obtain resolution of 10 [µm], we designed the mechanism which keeps constant the focal length between the object and the lens. As a result, the width of slit ray was clear in the whole surface. A section image could measured exactly and enhanced the resolution.

This paper describes the characteristics of the radiated magnetic field caused by breaking arcs between a pair of Ag, AgDdO, AgSnO2 or Pd contacts in a DC 50V/1.9-5.0A circuit. For Ag contacts, in an interrupting current less than 3.3A, the radiated magnetic field appears strongly during the metallic phase arc where the smaller the interrupting current is, the more the number of frequency spectra of the radiated magnetic field becomes. In an interrupting current more than 3.3A, the radiated magnetic field appears weakly during the metallic-gaseous transition period. For AgSnO2 and AgCdO contacts, there is a weak radiated magnetic field in the metallic-gaseous transition period and the smaller the interrupting current is, the stronger the maximum intensities of frequency spectra of the radiated magnetic field in the transition period are. For Pd contacts, the maximum intensities of frequency spectra of the radiated magnetic field do not change very much from the beginning to the end of the breaking arc, which do not depend on the interrupting current. From the experimental results, the maximum intensities of frequency spectra of the radiated magnetic fields are found to depend on the contact material. And their distribution depends on the impedance of the circuit containing the contacts that generates the breaking arc.

In clad contacts of bonded dissimilar metals used in relays and switches, the bonding state affects the switching performance of those devices. Examining the bonding state and analyzing the relationship between the bonding state and the causes of malfunction, such as welding of the contact, leads to improvement in reliability of electromechanical devices. In this experiment we examined, with an ultrasonic microscope, the bonding state in riveted clad contacts which had been subjected to load-breaks of in-rush current, and were able to demonstrate the causal relation of the bonding state with malfunctions of the contacts. The use of the ultrasonic microscope made it possible to perform a hitherto difficult detailed analysis of the bonding state of clad contacts. It was also confirmed that this was an extremely effective method for studying the relationship with switching performance.

Reliability of an electric contact can be defined by two parameters, contact resistance and wear, and the parameters of contacts operated in arcing condition are governed by the arc discharge. Thus the measurement on the relationship between the parameters and arc phenomena is necessary to improve the contact performance. The parameters for arcing electric contacts and problems were reviewed, and new concept for electric contact testing systems was proposed. Measurement with such an advanced system should be concurrent parallel measurement, quantitative measurement of degradation, systematic measurement, and analysis of arc discharge phenomena. Some examples of advanced measurement systems and new data obtained with such systems were described. Systematic results on relationships between condition and performance parameters were obtained by systematic measurement with systematically settled conditions, such as opening speed or material condition. A measurement method for the metallic phase arc duration was developed by the authors, and role of the metallic phase arc on contact performance parameters was found from interpretation of obtained data. The real-time surface profile measurement of an operating contact and the optical transient spectrum analyser for arc light radiated from breaking contact were also described.