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Contact bounce is a common phenomenon in the closing process of electromagnetic relays, which seriously affects the electrical contact reliability of the system. The whole closing process of flexible spring components consists of the free movement stage and the contact bounce stage, which increases the complexity of analyzing the electrical contact behaviors of electromagnetic relays. In this study, a novel nonlinear dynamic model of the flexible spring components in electromagnetic relays is established to analyze the physical mechanism of the electrical contact bounce. Considering the electromagnetic effect, flexible deformation, contact collision, and welding force, the proposed mathematical model can capture the dynamic closing process accurately and collect bounce parameters efficiently. The Kelvin–Voigt viscoelastic contact model is employed to evaluate the nonlinear contact force between the static and movable contacts. Based on the Galerkin method, the nonlinear equations of motion for the movable spring within electromagnetic relays are formulated. A series of experimental work are designed to measure the typical waveforms of displacements of the movable contact and currents in the coil during the closing process of the movable spring. Furthermore, the theoretical results are validated by comparing with the experimental data. The dependences of some key factors, including the structural, material, and electrical contact parameters on the contact bounce characteristics, are investigated explicitly. The theoretical results attest that the proposed model can accurately predict the dynamic behaviors of the movable spring, and the contact bounce can be effectively suppressed by adjusting the parameters of the flexible spring component. [ABSTRACT FROM AUTHOR]

Contact bounce is a common phenomenon in the closing process of the electromagnetic relay under capacitive loads. The investigations on the contact characteristics are mainly conducted by experimental methods. However, the experimental method is extremely complicated and time-consuming in structural design, and it cannot clearly reveal the mechanism of contact bounce. Therefore, a new theoretical model is proposed to investigate the dynamic characteristics of the electromagnetic relay under capacitive loads. The model allows for simulating dynamic process and collecting bounce parameters in a simple and effective way compared with conventional simulation and experimental methods. The physical mechanism of contact bounce for the electromagnetic relay is presented. The nonlinear contact force between the fixed and moving contacts is evaluated according to the Kelvin–Voigt viscoelastic contact model. The equations of motion considering the coupling of electromagnetic and mechanical fields are established. The theoretical results obtained in this study are validated by comparison with experimental data. The influences of the structural parameters, coil current, surge current, and contact resistance on the contact bounce are analyzed. The numerical results well demonstrate that the contact bounce can be effectively weakened by adjusting the parameters of contact spring and the mass of the moving contact. [ABSTRACT FROM AUTHOR]

Radio frequency (RF) coaxial switches have the advantages of high transmission frequency and power capacity and are widely used in aerospace, communications, military, science, and medical fields. In accelerated thermal cycle (ATC) test, a permanent deformation or displacement occurs in the contact system of RF coaxial switch caused by creep and the RF performance downgrades with the thermal cycle times. In this paper, a 3-D finite-element model of an RF coaxial switch was first proposed. The power loss in the contact system when the switch transmits high frequency and power signals was divided into the conductor loss and the dielectric loss, which were calculated separately. It was noted that conductor loss was the main part of power loss. Then, the power loss in the contact system was considered as the heat source, and the steady-state temperature field of the whole switch was calculated with Ansoft HFSS and Workbench. The temperature rise in an RF coaxial switch was calculated and verified by experimental testing. In order to predict the reliability and working life of RF coaxial switch in ATC test, a creep constitutive equation based on the Coffin–Mason method that has three undetermined coefficients was built. According to ISO204:2009 (Metallic materials-Uniaxial creep testing in tension), the samples of beryllium bronze for creep testing were produced, and two groups of creep testing in the condition of different temperatures and stresses were carried out to obtain the undetermined coefficients. Finally, the stress–strain deformation of contact system with the thermal cycle times was calculated based on the creep constitutive equation. The model of contact system was rebuilt, and the influence of creep on RF coaxial switch in ATC test was investgated. The analysis methods and conclusions presented in this paper have important theoretical significance and practical value for improving the performance and reliability of RF coaxial switch products. [ABSTRACT FROM AUTHOR]

Electrical lifespan prediction is one of the key problems for the designers of switching apparatus. It is of great necessity to develop empirical correlations between the design parameters and the electrical lifespan. In this paper, a novel method using the arc erosion mass as the prediction variable is proposed to predict the electrical lifespan of high-voltage direct-current (HVDC) relays. The arc current waveforms are measured, and the arc erosion mass during each breaking operation is calculated based on the relationship between the arc current and the arc erosion rate. The arc erosion mass is accumulated until it reaches a threshold value, which is determined by the electrical lifespan experimental results using HVDC products. It is found that the arc erosion mass linearly accumulates with the lifespan, which is very convenient in the electrical lifespan prediction. Experiments are carried out with a parameter-adjustable device similar to the actual HVDC relay structure. Effects of two key design parameters, the arc-blowing magnetic field flux density and the contact breaking speed, of the electrical lifespan are investigated. The magnetic field flux density is changed in the range from 40 to 80 mT, and the breaking speed is varied from 0.85 to 1.3 m/s. The relationships between the lifespan and the magnetic field flux density as well as the breaking speed are regressively constructed. It is shown that the developed relationships can be used for HVDC relay electrical lifespan prediction. [ABSTRACT FROM PUBLISHER]

DC power relay is a key electromechanical component widely used in electrical vehicles, photovoltaics, as well as more-electric aircrafts for energy managing, power conversion, and distribution. As the voltage and current increase due to relay switches, arc discharge becomes an unavoidable and significant issue during the operation of the dc high-power relay. Bridge-type contact and external permanent magnets are spontaneously employed in its arc chamber to accelerate the quenching of arc. In this paper, the complicated arc discharge plasma in a dc power relay has been investigated by using both experimental and numerical approaches. Initially, arc dwell and arc restriking characteristics during the arc motion phase are presented by analyzing the voltage and current waveforms and arc images acquired in carefully designed breaking experiments. The arc driven by a transverse magnetic field with a variety of flux densities and the influence of flux densities on arc voltage and dwell are preliminarily discussed based on the experimental results. Then, to reveal the arc physics and to determine the influence of transverse magnetic field on arc motion characteristics, a simplified model based on the magnetohydrodynamic (MHD) theory is built and three cases with different magnetic field are calculated. The simulated arc behaviors including distributions of the temperature and current density are presented. The mechanism underlying the influence of transverse magnetic field on the arc motion is analyzed according to arc root transfer and arc voltage variation. In addition, to understand the formation of the arc restriking, the critical breakdown electric-field strength inside the arc gap is also calculated based on streamer breakdown theory. The parameters in the space occupied by earlier arcs, as predicted by the MHD simulations, are used in the breakdown calculation. Results show that the critical breakdown voltage reduces remarkably along with growth of the operating voltage and breaking current, and the arc dwell time can be reduced by strengthening the external magnetic field within a reasonable extent. [ABSTRACT FROM PUBLISHER]