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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]

The consistency problem caused by the uncertainties in manufacturing process is a significant factor influencing the quality of electromagnetic device (EMD). The foundation of quality analysis and consistency optimization is the substantial calculation for the input-output characteristics of the product. As for EMD, the interaction of electricity, magnetism (permanent magnetism), and dynamics make the calculation quite complicated. At present, finite-element method (FEM) is a common method for calculating the output characteristics of EMD. However, FEM takes too much time for calculating, it is difficult to be applied for the quality analysis and consistency design of EMD that requires substantial calculation. In this paper, a new approach for the quality analysis and consistency design of EMD based on the approximate model has been proposed. First, the approximate model for calculating the EMD output characteristics is established on the basis of FEM simulation results. Second, using the approximate model, the quality analysis of batch products is conducted with Monte Carlo method. Finally, the optimal design for consistency is carried out with robust tolerance design method. The effectiveness of the method proposed in this paper is verified by the case study of a certain type of electromagnetic relay with permanent magnet. [ABSTRACT FROM AUTHOR]

As an analytical method with lumped parameters, the magnetic equivalent circuit method is usually constrained by its incapability of flux leakage and magnetic saturation compared with finite element (FE) method. We propose a new approach introducing compensation matrix Cm\times n to combine both methods. It requires a certain number of feature points by FE to compensate flux leakage at different positions and saturation extents at different coil currents, result precision within 5% and only second time consumed. Then, the approach is applied in dynamic modeling, design refinement, and performance optimization, where repetitive calculation of electromagnetic character is needed, and the results indicate the feasibility of the approach. [ABSTRACT FROM AUTHOR]

The elastic waves generated by traditional meander- line coil electromagnetic acoustic transducers (EMATs) propagate in two directions, overlapping the echo signals from defects with the same distances, and the defect echo signal is hard to distinguish from the edge-reflected signal when the EMATs are near the edge of a specimen. In this paper, a unidirectional EMAT with two meander-line coils is proposed. A finite element model is used to simulate the directivity of the Rayleigh and shear vertical waves generated by these EMATs. Six transducers are fabricated using the printed circuit technique. The unidirectional Rayleigh wave and shear vertical wave are tested, and the results agree well with the simulation. [ABSTRACT FROM AUTHOR]