Contact Bounce Research Articles

Material performance analysis and structure design of the A.C. contactor driven by MSMA

Contactors are extensively utilized in the control field. Enhancing the response speed and reducing mechanical tremors during switching-in hold great significance in improving contactor’s reliability. A novel A.C. contactor suitable for low-voltage environments has been developed based on the unique properties of the magnetic shape memory alloy (MSMA). It exhibited remarkable characteristics such as large dependent variables, fast response speed, and strong controllability. First, the magnetron characteristics of the MSMA were introduced. Then, the overall structure of the new contactor was designed based on the MSMA output characteristics and the contactor’s design requirements. Next, switching-in characteristics of the contactor under the drive signal were analyzed through simulation. Finally, an experimental measurement was carried out to test the performance of the prototype contactor during separating brake and switching in. The A.C. contactor driven by the MSMA could achieve a response speed of 9.8 ms. The contact movement in the switching process is smooth, which effectively avoids the occurrence of contact bounce in the closing process, which provides theoretical support for the development of the MSMA in the field of low-voltage electrical control application research.

Study on Relay Contact Bounce Based on the Adaptive Weight Rotation Template Matching Algorithm

In order to analyze the relay action process from an imaging perspective and further investigate the bounce phenomenon of relay contacts during the contact process, this paper utilizes a high-speed shooting platform to capture images of relay action. In light of the situation where the stationary contact in the image is inclined and continuously changing, a rotation template matching algorithm based on adaptive weight is proposed. The algorithm identifies and obtains the inclination angle of the stationary contact, enabling the study of the relay contact bounce process. By extracting contact bounce distance data from the images, a bounce process curve is plotted. Combined with the analysis of the contact bounce process, the reasons for the bounce are explored. The results indicate that the proposed rotation template matching algorithm can accurately identify stationary contacts and their angles at different angles. By analyzing the contact status and bounce process of the relay contacts in conjunction with the relay structure, parameters such as the bounce time, bounce height, and time required to reach the maximum distance can be calculated. Additionally, the main reason for contact bounce in the relay studied in this paper is the limitation imposed on the continued movement of the stationary contact by the presence of the relay brackets when the kinetic energy of the contact is too high. This phenomenon occurs during the first vibration peak in the vibration process after the moving contact contacts the stationary contact. The research results provide a reference for further studying the relay contact bounce process, optimizing relay structure, and suppressing contact bounce.

Reducing Contact Bouncing of a Relay by Optimizing the Switch Signal During Run-Time

Reducing Contact Bouncing of a Relay by Optimizing the Switch Signal During Run-Time

Digital circuit for switch contact bounce analysis

This article discusses the issue of studying the parameters of the bounce of electrical contacts of switches in digital systems. Digital circuits of bounce analyzer are described. The results of experimental studies of the behavior of electrical contacts of various buttons and switches are presented. It is shown that various electric switches have random and unique characteristics, which can be used to solve the problems of random numbers generating, identifying of digital devices and user’s authentication. Prototyping of the proposed circuits was carried out on Digilent ZYBO Z7-10 debug boards, digital circuits were designed in VHDL for the Xilinx Zynq-7000 FPGA chip.

Development of the error reducing method for the determination of the alternating current amplitude without the use of current transformers

The object of the research is methods of current amplitude identification without using current transformers. Most solutions are built on reed switches, which have a limitation of the operation speed due to the mechanical nature of the reed contacts. Therefore, the time duration is a random variable with a significant variation. Thus, the problem that needs to be solved is the reduction of the error of current amplitude identification associated with the mechanical properties of contacts. According to the conducted literature analysis, the presence of contact bounce of reed switches increases the errors of sinusoidal current amplitude identification approximately up to 8–10 %. The mathematical modeling allowed us to investigate this phenomenon and research its influence on the method. The suggested model was then approved via in-situ modeling. Consequently, to reduce the errors of measuring the current amplitude via a reed switch, the replacement with an analog or discrete Hall sensor was proposed. A mathematical model of the discrete Hall sensor operation and a method for identifying the amplitude of the alternating current were developed. During the experiment, it was found that the analog Hall sensor has a limitation in measuring currents of large rates, at which the discrete sensor worked stably. Hence, the last was chosen. It is worth noting that the study of the behavior of the Hall sensor was limited to the value of the alternating current amplitude, four times the opening current with an average error of less than 3 %. The method suitable for discrete Hall sensors simplifies and reduces the cost of the measuring instrument design. However, the practical implementation of the suggested method requires also the application of devices concentrating the magnetic field on the Hall sensor surface

Development of testing apparatus for investigating electromagnetic dynamics of contactors: A pilot study

It is easy to find electromagnetic contactors in modern electromechanical devices owing to their advantages, which encompass a simple structure, ease of use, and low cost. However, these devices also have inherent drawbacks, including heat dissipation, contact erosion, and inefficient power consumption during long-term operation. This has sparked interest in contact soft-landing, which aims to reduce issues like contact bounces, contact welding, and arcing. This paper presents the development of a testing apparatus for investigating the electromagnetic dynamics of contactors or mechanical relays, aimed at developing an open-loop model-based controller for contact soft-landing. Theoretical equations based on physical theorems are derived to describe the behavior of the electromagnetic coil under varying factors. Additionally, a pilot study was conducted using the proposed testing apparatus to explore the relationship between heat dissipation, flowing current, air gap, and the Lorentz force produced by exposing ferromagnetic material to the magnetic field surrounding the electromagnetic coil. The experimental and simulation results showed good fitting, with a normalized root mean squared error ranging from 2.5% to 4.5% for various scenarios. Notably, it was found that the flowing current passing through the electromagnetic coil can be controlled by changing the duty cycle of the pulse width modulation signal driving the conductivity of the MOSFET. However, the results suggest that a modulation frequency greater than 5 kHz is not suitable for driving the electromagnetic coil.

Behaviors and Mechanism of Electrical Breakdown in Short Vacuum Gaps Under Pulsed DC Voltage

A topology consisting of a mechanical bypass switch and a power semiconductor switch (IGBT and IEGT) in parallel is widely used in high-voltage flexible dc transmission converter and static var generator (SVG). The mechanical switch will close quickly when the power semiconductor switch fails, which will cut off the failure device to protect the whole converter valve. Therefore, the mechanical contacts of the bypass switch need to close fast (within 3 ms) without contact bounce, which could only be achieved if the gap between the two contacts is extremely short (approximately 1 mm). Vacuum interrupter (VI) is most suitable for this application due to its advantages, such as compact size, high safety, environmental friendliness, long service life, and hardly oxidized contacts. In this article, a vacuum test rig is built, and the electrical breakdown behaviors of the short vacuum gaps under continuous and pulsed dc voltages are studied. It is confirmed that breakdown voltage under pulsed dc voltage is much lower than that under continuous dc voltage owing to the free and weakly bound microparticles on the contact surfaces. Finally, a new model describing the breakdown mechanism is proposed to explain the behaviors revealed in the experimental test.

A Novel Nonlinear Dynamic Model for Predicting Contact Bounce of Electromagnetic Relays With Flexible Spring Components

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.

Molecular Dynamics Simulation of Nanodroplets Impacting Stripe-Textured Surfaces.

The dynamic behavior of droplets impacting on textured surfaces has an important influence on many engineering applications, such as anti-icing and self-cleaning. However, the mechanism and law of the effect of textured surfaces on the impact behavior of nanodroplets has not been fully revealed yet. In this paper, the molecular dynamics (MD) method is used to model the dynamic behavior of nanodroplets after impacting the solid surface with a striped texture. The influences of texture gap and texture angle on the real contact area, spreading factor, contact time, and bounce velocity of the droplet after impact are also quantitatively analyzed. It is shown that the striped texture produces significant anisotropy in the spreading and contraction behavior of nanodroplets after impact, and the anisotropy is more pronounced on the ridged texture surface than on the grooved texture surface. In addition, we find that the texture gap has little effect on the dynamic behavior of nanodroplets impacting the textured surface. However, as the bottom angle of the texture increases, the real contact area and bounce velocity of the nanodroplet increase significantly, while the contact time and spreading factor decrease. This work further elucidates the characteristics and mechanisms of nanodroplets impacting on stripe-textured surfaces and provides a theoretical basis for the design of nanostructured surfaces in relevant applications.

A novel MEMS inertial switch with frictional electrode

This paper presents a frictional MEMS inertial switch with aiming to solve the problems of short contact time and bounce. According to contact principle in MEMS inertial switch, a new enhanced contact method by friction is proposed and a frictional switch is designed. To compare the frictional switch with common rigid switch and flexible switch, three switches were fabricated by micro electroforming technology and tested by a standard dropping hammer system. The tested results show that the contact time of rigid switch, flexible switch and frictional switch is 13 μs, 85 μs and 620 μs, respectively. Both rigid switch and flexible switch have bounce problem, while frictional switch is closed stably without bounce phenomenon. Frictional MEMS inertial switch has great advantages in enhancing contact.

Dynamic study on the contact bounce of an electromagnetic contactor

Contact bounces of an electromagnetic contactor generate contact arc discharge which causes consumption and welding of contacts and shortening of a product lifetime. To reveal behavior of contact chattering and critical parameters of chattering duration, we perform dynamic study on the contact bounce of an electromagnetic contactor by building the 1-D physical model. The parameters of the physical components in the model are referred from designed values of a product and estimated from measurements of products and FEM analyses. We find the contact chattering duration in the simulation is 0.45 ms, which is consistent with result of chattering duration measurement of a product, 0 – 0.6 ms. Finally, we calculate sensitivity of chattering duration to each parameter and reveal that the initial and final load of the pressure spring and the mass of the moving and fixed contacts have some degree of impact to the chattering duration of the electromagnetic contactor.

Research on the Contact Bounce During the Closing Process of a Repulsion Mechanism Applied in a Superconductivity Direct-Current Vacuum Circuit Breaker

This paper studies the contact bounce during the closing process of a repulsion mechanism applied in a superconductivity direct-current vacuum circuit breaker. A multi-physics field coupling simulation model is established to describe the whole closing process for the repulsion mechanism. The relationship between the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> is obtained for the repulsion mechanism, where the V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is an instantaneous closing velocity for the movable contact just mating with the stationary contact at the first time, and the D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> is the maximum contact bounce distance. According to this relationship, the critical instantaneous closing velocity V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cri</sub> for the case of no contact bounce is determined. According to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cri</sub> , a novel oil buffer is designed to adjust the closing displacement of the repulsion mechanism to realize a nonclosing bounce. A prototype repulsion mechanism with an oil damper is developed. Its closing characteristics are tested and compared with the simulation results to verify the absence of a contact bounce.

Analyses of Electromagnetic Buffer Characteristics of Operating Mechanism for Fast Vacuum Transfer Switch

The electromagnetic repulsion model of 400 V/630 A/12.5 kA fast vacuum transfer switch (FVTS) is established using finite element method. The speed and characteristics of the contact bounce of the FVTS are taken as constraints, and the objective is to keep the reliable opening of the mechanism with allowable bounce. The deceleration of the fast operating mechanism in the process of opening and closing is realized by applying the reverse electromagnetic repulsion force. Moreover, the simulation results demonstrate that the electromagnetic buffer effect is available, and the allowable bounce opening of the operating mechanism has been obtained. Furthermore, this paper compares the buffering effects of three kinds of conditions, such as no electromagnetic buffering, 110 V electromagnetic buffering and 220 V electromagnetic buffering. It can be found that the electromagnetic buffering is a necessary part of the 400 V FVTS, and the dynamic characteristics are the optimal scheme when the 220 V electromagnetic buffering is applied. Based on the results of simulation, a FVTS experimental prototype is developed to prove the effectiveness of the design scheme.

Drop Bouncing Dynamics on Ultrathin Films

For drops to contact various surfaces, the removal of the interstitial fluid is the prerequisite to contact. While the conventional understanding is for drops to irreversibly spread on a film made of the same substance, we describe the dynamics of drops initiating contact yet carrying enough momentum to completely lift off of the substrate which we label as contact bouncing. We report new experimental results of the dynamics between drops impacting thin films described by the ratio of the liquid film hL to the drop with diameter D0 for the range of 0.004 < hL/D0 < 0.08. Using high-speed interferometry, we visualize the interfacial gas layer spatiotemporal signatures across the various film thicknesses and Weber numbers. We find that while increasing the deformability of the thin films enhances the gas entrainment phenomenon at early times, it also increases the rate of the gas purging rate, increasing the chance of contact just prior to the gas film retraction and drop lift off sequence. Drops which contact the liquid film during the retraction stage are able to bounce with <5% volume loss.

Theoretical Studies of Bounce in Rod-Type Microswitches

To improve reliability of microswitches, it is necessary to carry out theoretical studies of the switching process both at the moment of switching and at the moment of bouncing. The article presents a dynamic model of microswitches with elastic rod elements, which allows at the design stage to evaluate such basic performance characteristics as response time and contact bounce time. The proposed technique is based on representation of the solution to the differential equation of vibrations of an elastic element in the form of a linear combination of eigenforms and the application of the Bubnov-Galerkin method. Theoretical studies of bounce in a rod microswitch are carried out. It is shown that breakdown precursors of the spacer spring are an increase in the switching time and the time of the first separation in case of bouncing.

Eliminating the contact bounce of AC contactor based on speed feedback

SummaryContactor bounce has a serious impact on its electrical life and closed reliability in the process of closing the main circuit. Controlling the contact movement is one of the effective ways to reduce the bounce effect. In this paper, the contact movement characteristics are concerned directly. A big speed and small acceleration of contact are expected to complete the closure. The mathematical model of the circuit and the magnetic circuit are established, and the dynamic characteristics of the electromagnetic system are analyzed. The closed‐loop control system of contact motion characteristic based on speed feedback is constructed, and the speed tracking effect is improved effectively by fuzzy control. The experiment results showed that the control method proposed is correct, and the actual speed curve of the contact was consistent with the planned motion curve. The contact speed of the contact decreases obviously, which can achieve the goal of restraining the bounce of the contact.

A New Theoretical Model to Study the Closing Bounce Characteristics of the Electromagnetic Relay Under Capacitive Loads

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.

Nanodroplets impact on surfaces decorated with ridges

The dynamics of droplets impacting on solid surfaces are directly related to a variety of engineering applications. As some industrial processes have been refined to the nanoscale, research interest in nanodroplets impact is growing. In this work, molecular dynamics (MD) is employed to investigate the impact processes of nanodroplets on superhydrophobic surfaces decorated with triangular nanoridges. We confirm that the decorated nanoridges can significantly promote the bouncing performance of nanodroplets, including enlarging the bounce domain, reducing the contact time, and enhancing the bounce velocity. We identify five distinct bounce modes for nanodroplets on the nanoridged surfaces, and the variation laws of contact time and bounce velocity of nanodroplets are determined by the characteristics of these bounce modes. Configuration of nanoridges can influence the variation laws of contact time and bounce velocity through changing the bounce modes of nanodroplets. The restitution coefficient can be piecewise fitted as the power functions of the impact Weber number of nanodroplets, regardless of the droplet diameters and ridge configurations. This work elucidates the characteristics and mechanism of nanodroplets impacting on the nanoridged surfaces, which is conducive to the design of nanostructured surfaces for related applications.

A Sequential Adaptive Control Strategy for the Contact Colliding Speed of Contactors Based on Fuzzy Control

In the making process of a contactor, the fast collisions of the movable contact and the static contact lead to the contact bounce, which greatly reduces the electrical life of the contactor. In this article, a neural network model is used to estimate the contact colliding speed and a fuzzy logic controller is designed with the contact colliding speed as the feedback. By controlling the excitation time of the contactor, the contact colliding speed successively approximates a given smaller reference value, thus, the contact bounce is inhibited. The results of the cosimulation show the theoretical feasibility of the proposed scheme. In addition, three contactors of different types are used for an experiment, and the results show that the reduction in the contact bounce time is more than 70% and that the proposed control strategy is universal.

Run-to-Run Control With Bayesian Optimization for Soft Landing of Short-Stroke Reluctance Actuators

There is great interest in minimizing the impact forces of reluctance actuators during commutations, in order to reduce contact bouncing, acoustic noise, and mechanical wear. In this regard, a run-to-run (R2R) control algorithm is proposed to decrease the contact velocity, by exploiting the repetitive operations of these devices. The complete control is presented, with special focus on the optimization method and the input definition. The search method is based on Bayesian optimization, and several additions are introduced for its application in R2R control, e.g., the removal of stored points and the definition of a new acquisition function. Additionally, methods for the input parameterization and dimension reduction are presented. For analysis, in this article, Monte Carlo simulations are performed using a dynamic model of a commercial solenoid valve, comparing the proposed search method with two alternatives. Furthermore, the control strategy is validated through experimental testing, using several devices from the same ensemble of solenoid valves.