Basic features of fretting and factors affecting its deleterious effects on the performance of electrical/electronic connection were reviewed. It was shown that although the fretting cannot be eliminated completely, its deleterious effects can be substantially reduced by lubrication and also connection design.

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Break arcs are generated between silver electrical contacts in a DC 42V-10A resistive circuit. Break arcs are driven by the radial magnetic field. The magnetic field is formed between the electrical contacts with a permanent magnet embedded in the cathode. The arc motion is taken with a high-speed camera and contact surfaces are observed after break operations. Experimental results with the magnet are compared with those without the magnet to confirm the effect of the embedded magnet. For break operations with the magnet following results are shown. Break arcs are rotationally driven by the radial magnetic field in the direction according to Lorentz force. The shortening effect of the arc duration is confirmed. The traces of the arc spots on the contact surfaces are ring-shaped, wide and uniform. This result shows the prevention effect of local erosion of electrical contacts. The rotational frequency of the break arc depends on the Lorentz force with the radial magnetic field.

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Using the transient current switch circuit in parallel with the energizing switching contacts for timely control of breaking operation, the increase of contact voltage is suppressed at the last stage of the breaking of electric contacts. Breaking contact voltage V_c and current I_c of electromagnetic relays with Ag contacting electrodes were measured with 12.5-50V and 0.1-20A for two hinge springs (Spring constants; 2N/mm and 0.2N/mm). The current-decreasing process was clearly measured at the melting voltage U_m. After V_c = U_m, the breaking time of contact current did not depend on mechanical motion controlled by the two hinge springs and energizing power-supply voltage, but depended on the contact current. The residue of melt electrode was observed optically as a white fusion spot, with radius depending on the energizing current.

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Using the transient current switch circuit in parallel with the energizing contacts, the slow decay of the contact current due to thermal fusion of metal was observed just after the contact voltage exceeded the melting contact voltage U_m. At that time, the contact voltage was higher than the boiling contact voltage U_b. These results contradict Holm's φθ theory. A new melting model of breaking mechanical contact is proposed. The area surrounding a cluster of contacting a-spots melts, the melt metal diffuses, and the contact spot thermally shrinks. Including the metal phase transition from solid to liquid, the increase of contact resistance is introduced to the electric circuit analysis. The numerical analysis agrees qualitatively with measured V-I characteristics.

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The liquid metal current limiter (LMCL) is a possible alternative to limit the short current of power system due to its special merits. This paper is devoted to the investigation of the arc behavior in liquid metal GaInSn for current limiting application. Firstly, the arc evolution including arc initiation, arc expansion and arc extinguish is observed through an experimental device. The resistance of arc and the self healing property of liquid metal are described. Subsequently, the arc erosion on electrodes is presented with its causes analyzed. Finally, the arc characteristics with the influence of rise rate of prospective current and channel diameter are discussed in details.

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Electrical contacts are the most important parts of electrical circuits, and many reliability problems of the circuits are related to contact failure. The contact resistance is one of the important factors for assessing connector reliability, and thus the prediction of contact resistance is essential to designing electrical terminals. In this study, embossments, each 1mm to 3mm in radius, were brought into contact with flat planes to simulate the point of contact on a terminal, and the contact resistance was measured using a four-probe method under a load up to 40N. Copper alloy samples, each plated with tin or silver and having an embossment of 1mm to 3mm in radius, were used and the visually clear indentations resulting from the embossment to plane contact were measured to determine their areas. Since the contact resistance is dependent on the contact area, an FEM analysis must be carried out to determine the contact areas correctly. In this paper, an elasto-plastic FEM analysis was performed taking the plating layers into account, and a method was established to make precise determination of the contact areas for different shapes of contacts and loads. The resultant contact areas were used to calculate the contact resistance, which showed a good agreement with experimental results. It was established that the load-resistance curves can be predicted on the basis of the shapes of the contacts as well as plating.

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It is necessary to know how the contact voltage and contact area vary with time to clarify the physics of contact lifetime and contact resistance. In this paper, to clarify the effect of the heating value on the diameter of the contact area, the variations of the contact voltage and contact diameter with time are measured at a low-speed breaking contact near the thermal equilibrium condition under which a stable bridge is generated. The effect of the heating value on the relationship between the contact diameter and the length of the bridge at breaking is also discussed. In the results, the contact voltage waveform was found to be macroscopically proportional to the displacement of the moving electrode l_c. On the other hand, the contact diameter d_c decreased slightly with increasing l_c. At all currents investigated d_c decreased when l_c increased. The length of the bridge at breaking was increased by increasing the current. A large heating value of the contact area resulted in a long bridge because the volume of the melted metal increases.

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The cooperative characteristics of electromagnetic relay's attraction torque and reaction torque are the key property to ensure its reliability, and it is important to attain better cooperative characteristics by analyzing and optimizing relay's electromagnetic system and mechanical system. From the standpoint of changing reaction torque of mechanical system, in this paper, adjusted parameters (armature's maximum angular displacement α_{arm_max}, initial return spring's force F_{initi_return_spring}, normally closed (NC) contacts' force F_{NC_contacts}, contacts' gap δ_gap, and normally opened (NO) contacts' over travel δ_{NO_contacts}) were adopted as design variables, and objective function was provided for with the purpose of increasing breaking velocities of both NC contacts and NO contacts. Finally, genetic algorithm (GA) was used to attain optimization of the objective function. Accuracy of calculation for the relay's dynamic characteristics was verified by experiment.

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An electromagnetic relay (EMR) is widely used in automatic control field, and its dynamic characteristics play a significant role in EMR researches. According to structural features of the EMR, a dynamic characteristics testing and analyzing system (DCTAS) based on CCD digital image processing technique is designed and implemented. By using the DCTAS, the dynamic characteristics (include displacement, velocity, acceleration and force characteristics) of EMR whose operating time is less than 12ms and armature travel is less than 10mm can be investigated. The comparison of testing data obtained by the DCTAS and that of by a high speed camera indicates the validity of the system to EMR dynamic characteristics testing.

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Electrical life is an important parameter to estimate the reliability of a relay, and it is greatly affected by load current. In order to shorten the time of life test, load current stress accelerated life tests were carried out by using a life test system designed for relay in this paper. During the life test, many parameters such as the contact resistance, the closing time and the over-travel time of relay were measured for each operation to identify the failure modes. After the life test, the failure mechanisms under each current stress, which cause the same failure mode, were analyzed by investigating the variations of parameters and observing the morphology of contact surface. In addition, for the purpose of further studying the consistency of failure mechanisms between different current stress, a Weibull statistical analysis was adopted to estimate the shape parameter of Weibull distribution because the same shape parameter means the same failure mechanism. Finally, a statistical model for estimating the lifetime under load current stress was built. The research methods and conclusions mentioned in this paper are meaningful to perform the accelerated life tests for other types of relays.

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According to a new kind of permanent contactor, this paper analyses the dynamic behavior of the contactor with and without current-feedback system. And it presents a method to obtain the dynamic characteristics of the contactor with current-feedback system. The experiments prove that the method is correct. Then, it compares the contactor without current-feedback system with the one with current-feedback system. The result shows that the contactor with current-feedback system can avoid this flaw of the contactor without current-feedback system.

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Unpredicted contactor failure can interrupt production and affect the uptime and throughput of manufacturing. Usually the life of a contactor is based on the manufacturers' life test data. However, due to the way of how the contactor is operated and the environment it is operated in, the working life of a contactor can vary significantly. In this paper, a novel technology has been investigated to predict potential failures of DC actuated contactors by monitoring their DC coil current and contactor currents. Three parameters are derived from this set of data to monitor the health of contactors: contact over-travel, armature pull-in time and coil current differential. Contact over-travel provides information on the remaining life of contacts and coil current differential provides indication of contact weld and carrier jam due to debris. The armature pull-in time provides information on contactor closing speed. Prototype contactors have been built and AC4 tests have been carried out for evaluation. Test results show that the contact over-travel parameter agrees well with contact mass loss data taken after contactors failed. The derived armature pull-in time agrees well with that measured by a laser displacement sensor. The defined parameters provide effective monitoring and prediction of potential contactor failures.

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This paper presents an accurate and systematic method to model the equivalent circuit of pulse generator in the electrical fast transients/burst test (EFT/B). Firstly, a new analytical expression is presented to express the generator's charging and discharging process under open-condition (1000-Ω), which all its coefficients are determined according to the output waveform specified by the manufacturer. And then, with adoption of the step source, the transfer function of the pulse forming network in Laplace domain is deduced, which is ready for the network synthesis. Based on above discussion, the parameterized method and the technique of constant-resistance are adopted for the network synthesis. Finally, the equivalent circuit is renormalized and improved to meet the specification under matching-condition (50-Ω). In this way, the equivalent circuit of EFT/B generator is obtained and can be adjusted conveniently to satisfy the different manufacturers. The PSPICE simulation with a certain load is validated by measurement.

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This paper proposes the design of a driver to deal with a thin-disc central supporting structure ultrasonic actuator based on the vibration modes and the equivalent circuit. In order to gain the electromechanical match at resonant frequency, a spectrum analyzer should measure admittance for driving piezoelectric ceramics. The virtual analyzer also investigated the characteristics of a MODEL-E equivalent circuit based upon the admittance-frequency response. The inherent capacitance from an ultrasonic actuator became the partial component in the design of a resonant circuit. IsSpice software is introduced to simulate as well as the experimental results has demonstrated a high agreement related to the conceptual design and practical implementation for the driving circuit.

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This study utilizes a new adaptive sense current controller to get an accurate power supply. The proposed controller effectively reduces output ripple voltage of converters operated over the load current range. This reduction is realized using an adaptive sense current circuit that automatically adjusts the inductor current according to operational conditions. The proposed boost converter is designed and fabricated with a standard TSMC 3.3/5V 0.35-µm 2P4M CMOS technology. The experimental results show that the power-conversion efficiency of the proposed boost converter is 2-5% higher than that of the conventional converter with a current-limited circuit. The proposed circuit greatly reduces (i.e. by 76%) output ripple voltage compared with the conventional circuit at a 10mA loading current.

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This paper introduces a new folding amplifier in a folding and interpolating 10-b ADC. The amplifier consists of current mirrors and differential stages. Only one current source is exploited in cascaded differential pairs, which reduces the power consumption significantly. In the folding circuit, the interpolation is implemented with a current division technique. An experiment of the amplifier in 10-b folding signal has been integrated in a single-poly four-metal 0.35µm CMOS process. The simulation in 10-b folding ADC shows that power consumption is 225mW at the sampling speed of 250Msample/s and the power supply of 3.3V. The preliminary experiment indicates the current steering folder and digital bits operate as expected.

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A 0.18µm 1.5V/50mA stability-enhanced low dropout regulator (LDO) is presented. A multi-path error amplifier and a split pass device structure are utilized for pole-zero pair compensation. The proposed LDO can be stable without a load capacitor and also stable with different combinations of load capacitors and equivalent series resistance.

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A new type of mode converter that converts TE₃₀ to TE₁₀ mode is proposed. As an example of the ease of fabrication, holes can be drilled at the top of a metallic waveguide and dielectric rods inserted. This converter is useful for application as a power divider or power combiner.

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A fully integrated CMOS wideband Low Noise Amplifier (LNA) operating over 2.3-7GHz is designed and fabricated using a 0.18µm CMOS process. The proposed structure is a common source-common source (CS-CS) cascode amplifier with a coupling capacitor. It realizes both low voltage drop at load resistor (R_load) and high gain over 2.3-7GHz with simultaneous noise and input matching and low power consumption. This paper presents the proposed design technique of a wideband LNA, and verifies its performance by simulation and measurement. This wideband LNA achieves an average gain (S21) of 16.5 (dB), an input return loss (S11) less than -8dB, a noise figure (NF) of 3.4-6.7dB, and a third order input interception point (IIP3) of -7.5-3dBm at 2.3-7GHz with power consumption of 10.8mW under 1.8V VDD.

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A novel method for tailoring the beam profile of laser diodes that employs Lloyd's mirror interference is investigated. The beam profile in the vertical direction is controlled by inserting a GaAs mirror below the active layer. The experimentally obtained trends are successfully modeled by numerical calculations using Huygens' integral.

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In this paper, a novel eight-way Ka-band spatial power combining structure based on SIW/HMSIW is presented and studied. The power-combining structure is realized by transitions between HMSIW and parallel multiport planar microstrip lines. The power combiner is designed and fabricated in 33.5-35GHz. The measured results show a good agreement with simulation and a combining efficiency of 72% is achieved at 34.3GHz.

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