This paper presents a comprehensive explanation of the formation of the electric arc between opening contacts in a current carrying electric circuit. As the contacts begin to open a molten metal bridge forms between them. The rupture of this bridge and the initial formation of the electric arc are studied in both atmospheric air and vacuum using experiments to determine the direction of metal transfer between the contacts as a function of time after the rupture of the molten metal bridge. High speed streak photography is also used to show the rupture of the molten metal bridge and the initial formation of the electric arc. Analysis of these data show that a very high-pressure, high-temperature metal vapor zone exists between the contacts after the rupture of the molten metal bridge. Under this condition a pseudo-arc forms where current is carried by metal ions and an anomalous, high net transfer of metal to the cathodic contact occurs. The pressure in this region decreases rapidly and there is a transition to the usual electric arc, which still operates in the metal vapor. In this arc the current is now mostly carried by electrons. The data shows that there is still a net transfer of metal to the cathode, but now its volume is a function of the arcing time.

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Break arcs are generated between electrical contacts in a DC 42V resistive circuit. Contact materials are Ag/SnO₂ and Ag/ZnO. Circuit current when contacts are closed is varied from 5A to 21A. The radial magnetic field to drive break arcs is formed between the contact gap with a permanent magnet embedded in the cathode. The arc motion is observed with a high-speed camera. Experimental results with the magnet are compared with those without the magnet. Following results are shown. Similar experimental results to pure silver contacts are obtained for Ag/SnO₂ and Ag/ZnO contact pairs. The rotational motion of the break arcs and the shortening effect of the arc duration are confirmed. The ring-shaped, wide and uniform traces are observed on the contact surfaces after break operations. This result shows the prevention effect of local erosion of electrical contacts and the reduction of total amount of contact erosion. The rotational frequency f is increased with the increase of the arc current I_arc. These results for Ag/SnO₂ and Ag/ZnO contact pairs are similar to the results for pure silver contacts in our previous experiments. The rotational frequency of the break arc for the Ag/SnO₂ and Ag/ZnO contacts is lower than that for the pure silver contacts.

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Break arcs are generated between pure silver electrical contacts in a DC high-voltage resistive circuit. The break arc is driven by the external magnetic field of a permanent magnet from horizontal direction of contacts. Electrical contacts are separated at constant opening speed at 75mm/s. The maximum supply voltage is 300V. The maximum circuit current when electrical contacts are closed is 20A. The maximum output power of the supply is limited to 6.0kW. The gap between the contacts and the magnet is defined as x. The gap is varied from 2.5mm to 10.0mm to change the magnetic flux density that affects the break arc. The break arc is observed with a high-speed camera. The effect of the magnetic field on the arc duration was examined. As a result, break arcs are successfully extinguished by the transverse magnetic field when the gap x is 2.5mm. Then the length of the break arc just before lengthening of the break arc L and the Lorentz force that affects the break arc F are examined. The length L was almost constant for each gap x and independent of the circuit current I and the Lorentz force F. The break arc is driven by the magnetic field when the arc length reached a certain length that was determined by the strength of the magnetic flux density.

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Gas flow in arc quenching chamber has an important effect on the interruption capability of low voltage circuit breakers. In this paper, based on a simplified model of arc chamber with a single break, which can be opened by the electro-dynamics repulsion force automatically, the effect of different vent configurations including middle vent and side vent on the interruption performance is investigated. First, the experiments are carried out to compare the different performance in the interruption process between middle vent type and side vent type. In addition, according to the experimental model, a 3-D magneto-hydrodynamic model was developed by adapting and modified the commercial computational fluid dynamics software FLUENT. The simulation results show the same trend in arc motion as explained in the experimental conclusions in theory.

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The dynamic characteristics are the key issues in the optimum design of a permanent magnetic actuator (PMA). A new approach to forecast the dynamic characteristics of the multilink PMA is proposed. By carrying out further developments of ADAMS and ANSOFT, a mathematic calculation model describing the coupling of mechanical movement, electric circuit and magnetic field considering eddy current effect, is constructed. With this model, the dynamic characteristics of the multilink PMA are calculated and compared with the experimental results. Factors that affect the opening time of the multilink PMA are analyzed with the model as well. The method is capable of providing a reference for the design of the PMA.

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We propose and demonstrate a new type of field installable optical connector that enables us to realize physical contact connection without polishing the fiber endface by using a sharpened fiber endface and the compression force of buckled fiber. We confirmed that all the assembled connectors achieved physical contact connection without the fiber endface being polished, and provided good optical performance with a low insertion loss of 0.08dB and a high return loss of over 49dB.

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The paper presents the state of knowledge about thermal-erosion processes in contacts of low-voltage switching devices for power engineering on switching currents under short-circuit conditions. The graphical models of the short arc and the distribution of arc power introduced into contacts are shown. The method for measurements of a contact temperature during an electric discharge has been elaborated. The obtained test results are presented, i.e. changes of a contact temperature as a function of arc parameters such as current, energy, and integral ∫ idt. The tests have shown that a “break point” exists on the curve expressing the relationship between a temperature rise and arc parameters in the range of high currents. The location of this point is dependent on a diameter of contacts and a value of current, and is associated with thermal energy delivered to electrodes. It has been observed that for each diameter of contacts there exists such value of an energetic quantity of arc (current, ∫ idt, energy), at which diameters of arc roots are the same as a contact diameter. Above this value, the shape of a curve is changed. The obtained results explain and confirm the discontinuity of a curve expressing a contact arc erosion as a function of current, which was observed earlier by the other research workers.

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Similarities and differences of the thermal analysis issues between the intelligent and general AC contactors are analyzed. Heat source model of the magnet system is established according to the unique control mode of the intelligent AC contactor. Linking with the features common of the two kinds of contactors, the extension of the thermal analysis method of the general AC contactor to the intelligent AC contactor is demonstrated. Consequently, a comprehensive thermal analysis model considering heat sources of both main circuit and magnet system is constructed for the intelligent AC contactor. With this model, the steady-state temperature rise of the intelligent AC contactor is calculated and compared with the measurements of an actual intelligent AC contactor.

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The phenomena of retrograde motion of arc in the atmosphere under transverse magnetic field were studied. AgSnO₂ contacts were set in DC resistive and inductive circuits, respectively. The break voltage was 28V, the current ranged from 1 to 5A, and the magnetic flux density changed from 0 to 100mT. A high speed camera and an oscilloscope were used to record time variations of arc images, voltages and currents, simultaneously. Different from previous experiment results, the arc motion showed three stages which was more obvious under larger magnetic flux density in inductive circuit. It was also found that the arc movement was closely related with the arc voltage. Explanation to the retrograde motion under such conditions was given.

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Usually the contact voltage drop or contact resistance of electromagnetic relays is observed only to identify if the contacts are failure or not on the manufactures' life tests. However, it is difficult to reveal the contact performance degradation because the variation of contact resistance may not be obvious. In this paper, a new life test technology was investigated to analyze the contact failure mechanisms and degenerative processes of electromagnetic relays by measuring their time parameters including closing time, opening time, over-travel time, rebound duration and gap time during each operation. Moreover, for the purpose of verifying the time parameters, the contact motion and contact morphology during life test were record by using a high speed camera. Both the variations of time parameters and information obtained from photos taken by high speed camera show that it involves three different degenerative phases during the whole life of a relay. The results also indicate this method is an effective technology to discriminate and diagnose the failure mechanisms for electromagnetic relays.

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In an automotive fuel pump system, a small DC motor is widely used to drive the pump and driven by a automotive battery. Recently a bio-fuel, usually a mixture of gasoline and ethanol has been used due to shortage of gasoline and environmental aspect. It affects strongly the performances of a DC motor, especially commutation phenomena, what kind of fuel is used. Therefore the authors have started to investigate the influence of ethanol on the commutation phenomena. They have been reporting the wear of brush and carbon flat commutator in gasoline and ethanol so far. In this paper commutation period, arc duration, brush and commutator wear are examined in ethanol 50-gasoline 50%. Brush wears are very small compared with the previous results. Namely in the present test a mechanical sliding wear is predominant rather than erosion by arc due to short arc duration. Further, an area eroded by arc is observed to re-appear as a sliding surface. From these results a threshold arc energy between arc erosion and mechanical sliding wear is obtained, and a wear model is proposed to explain the above wear pattern on the sliding surface.

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Adjustability is an important function of the magnetic release for modern molded case circuit breakers. Based on virtual prototype technology, an automatic prediction method is proposed to design reasonable reactive spring parameters for this kind of magnetic release. 3-D finite element method is adopted to calculate the static characteristics of the magnetic release. Then the dynamic characteristics of the magnetic release can be simulated taking into account the variation of the spring parameters with multi-dynamics method. The calculation results have been verified by the relevant experiments. It demonstrates that the proposed method is feasible to perform the design task.

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In this report, Focused Ion Beam (FIB) — SEM technique was applied to observe the tin plated fretting contacts. Spatial distributions of tin, tin oxide and so on have been confirmed quantitatively in two plating thickness of 1 and 5µm.

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In order to clarify the physics of contact life time, the relationship between heat capacity of holder and shape of bridge (length and diameter) is discussed in this paper. The AgPd₆₀ alloy is chosen as electrode material. Two holders with different heat capacity are comprised of copper plate and cylinder. The shape of the bridge at the low speed breaking contact is observed by using the high speed digital camera. It was demonstrated that the shape of the bridge is changed by the response and distribution of the temperature.

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This paper represents a low noise second harmonic oscillator using mutually synchronized Gunn diodes. A multi-layer MIC technology is adopted to reduce the circuit size of the oscillator. The oscillator consists of Gunn diodes, slot line resonators and strip lines. By embedding Gunn diodes in the slot line resonators, a harmonic RF signal can be generated very easily. The strip lines are used for the power combining output circuit. The shape of slot line resonator is square in order to achieve the low phase noise and the suppression of undesired harmonics. The second harmonic oscillator is designed and fabricated in K band. The output power is +8.89dBm at the design frequency of 18.75GHz (2f₀) with the phase noise of -116.2dBc/Hz at the offset frequency of 1MHz. Excellent suppression of the undesired fundamental frequency signal (f₀) of -33dBc is achieved. Also, the circuit size is reduced by three-tenths relative to that of the previously proposed circuit.

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A linear model for feedforward ring oscillators (FROs) is developed and oscillator characteristics are analyzed using the model. The model allows prediction of multiple oscillation modes as well as the oscillation frequency of each mode. The prediction agrees well with SPICE simulation results.

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Single event transient (SET) effects on original static cascade voltage switch logic (CVSL) exclusive-OR (EX-OR) circuits have been investigated using SPICE. SET simulation results have confirmed that the static CVSL EX-OR circuits have increased tolerance to SET. The static CVSL EX-OR circuit is more than 200 times harder than the conventional CMOS circuit.

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Readout characteristics of a near-field optical disk with an acute-edged metallic nano-aperture were investigated. The electromagnetic field distributions of the near field around the aperture were analyzed, and the far-field scattering of the waves transmitted through the phase change disk was calculated by finite-difference time-domain method into which motion equations of free electrons were incorporated. Adjusting the edge angle of the aperture increased the field intensity of near-field light. The influence of the edge angle on output through the recorded mark was also investigated. It was found that there is an optimum edge angle that differs depending on the aperture width.

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An empirical dispersion formula is proposed and experimentally verified considering higher order modes of the conductor-backed coplanar waveguide with via holes. For this purpose, an effective dielectric constant is extracted up to 100GHz from measured S-parameters. By fitting the extracted data, an empirical equation is extracted. The simulation of the Gaussian pulse transmission and the comparison results with the modeling data validate the reported expression.

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This paper proposes a compact ultra-wideband filter, which skillfully utilizes the magnetic and capacitive coupling to obtain sharp rejection. And, the filter contains a small number of lossy elements, thus the low insertion loss and compact size will not be compromised. The measured results show that the filter prototype has a measured 3dB fractional bandwidth of 128% from 2.8GHz to 11.4GHz, a minimum insertion loss of 0.3dB within the passband, a superior 20dB stopband rejection from 12.4GHz to 24GHz, and a very compact circuit size of 0.23λ×0.31λ, where λ is the guided wavelength of the microstrip structure at the center frequency f₀ = 7.1GHz.

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A novel resonant eight-way divider/combiner based on a double-layer finline is presented and studied. Experiments on the compact eight-way passive divider/combiner demonstrate a minimum overall insertion loss of 1dB at 35.3GHz, and the inserting loss across 34-36GHz is less than 1.9dB.

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