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 12 ms and armature travel is less than 10 mm 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.

Generally, the failure rate of a sealed relay is regarded as a constant value, no matter where and how it is used. However, the failure processes of sealed relays won't be the same under different conditions, even for one relay, its failure rate also will be changed during operations. This paper studies the failure process of a kind of sealed relay by analyzing the variations of its time parameters. Among contact resistance and all those time parameters, it is found that closing gap time can indicate the failure process of tested relay very well. For the purpose of verifying this conclusion derived from time parameters, the contacts are observed by microscope after the tested relay failed. Both theoretical calculation result of contacts gap and photos taken by microscope show that the hypothetic failure mode derived from time parameters is reasonable. Based on the failure analysis, the paper also proposes a dynamic reliability estimation method with closing gap time.

Cu-Mo alloy carries forward not only high electrical conductivity and high thermal conductivity from Cu but also high hardness from Mo, which makes it a promising potential application in electrical contact fields. In this paper, arc characteristic and erosion characteristic of Cu-Mo contacts are studied with a bridge-type contact high speed break mechanism on DC270 V/200 A load condition. And in each experiment group, 2500 times break operations are carried out. During every break operation, a high-speed AD card is used to record voltage and current signal of the arc, a high-speed camera is applied to record arcing process, and the temperature of contacts and arc are acquired by thermocouple and spectrometer, respectively. The mass and contact resistance of contacts are measured before and after every group experiment. Besides, the photograph of contact surface is taken by SEM to help analyze the erosion characteristic. The comparison between Cu-Mo contacts and Cu contacts indicates that although Cu contacts have a better electrical conductivity and thermal conductivity, Cu-Mo contacts can decrease the temperature of arc to prevent thermal breakdown, and they are also harder to be ablated and have a longer life span.

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 28 V, the current ranged from 1 to 5 A, and the magnetic flux density changed from 0 to 100 mT. 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.

Research on the electromagnetic compatibility of functional module composed of two independent electromagnetic relays in a hermetically sealed shell is the technical foundation for integration and miniaturization of electronic equipment in the future. In this paper, 3D finite element method (FEM) was used to analyze the dynamic characteristics of twin-type relay interfered by uniform constant magnetic field and identify the sensitive direction in which the relay was easily interfered. The models of twin-type relay in three working states were founded. Through simulation and analysis, it was found out how the operation time and electromagnetic torque of twin-type relay changed with the outer interfered magnetic field. When the relay was on the point of operation failure, the critical value of magnetic field was calculated through simulation. The simulation results of the dynamic characteristics of twin-type relay agree well with the experimental data. The conclusion in this paper is of great value for research on the electromagnetic compatibility of relay functional module.

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.

Axial and transverse magnetic fields are widely used in many kinds of switches to decrease the arc erosion. In this paper, the influence of these two kinds of magnetic fields on the arc phase transition was studied particularly for AgSnO2 contacts breaking a 28 V/25 A circuit. The experiments were carried out under resistive and inductive loads in an atmospheric environment. The relationships between flux densities ranging from 0 to 200 mT and the arc duration were obtained. It was found that the transverse magnetic field was more efficient in balancing the arc phases and decreasing the arc erosion. The results can be used to guide the design of arc extinguishment systems in DC high power relays.

Hermetically sealed electromagnetic relays (EMR) are widely used for high reliability control and executive systems as a device mechanically transferring signals. Now they are more indispensable in space engineering, such as rockets, satellites and other ground attachment, but which mechanical atmosphere is too harsh. So dynamics response of EMR is needed to satisfy particularity of such mechanical atmosphere. In this paper, a typical hermetically sealed EMR structure is modeled by using finite element analysis software-Nastran. In the meantime the equivalent spring elements are introduced to simulate the contact of normally closed contacts, and the contact between armature and iron stopper. Therefore dynamic performance of EMR under different mechanical environment, including sinusoid vibration and shock condition is investigated completely. The factors affecting normal modes and dynamic response of EMR are analyzed. Comparisons show good correlation between experimental and numerical results.

A method which uses the moving time and the over travel time of contact to discover the characteristics of contact and the reliability of aerospace relay is proposed. The Gauss-Newton method and its improved form (Macalto method) are used to identify the nonlinear mathematical model of the parameter during armature initial moving period, which is from the coil is energized at a rated voltage to the moment the armature begins to move. The validity of the method is verified by results of actual experiments and analysis.

Vibration characteristic of electromagnetic relay (EMR), including modal and frequency response are important for increasing operational reliability in mechanical environment. The switching contact system, as function execution component of EMR, is the important parts in this product. This paper presents a dynamic model of contact system by introducing Hertz contact theory, and discusses weakly nonlinear oscillation character. Quasilinear simulation analysis using by finite element analyzing software-NASTRAN is investigated. The factors affecting contact vibration characteristic are determined. Finally, theory analysis and simulation results are verified by the vibration test. The model starts from a typical contact system of EMR, but the approach can be applied to other switching electro-mechanical devices.

This paper presents the electrical contact behaviors of Au-plated material at super low making and breaking velocity conditions by introducing our new designed test rig. The fundamental phenomena in the contact voltage and contact force versus piezoactuator displacement curves were investigated under the load current of 1A and velocity of 50,nm/s. From the repetitive experimental results, we found that the adhesion phenomena during the unloading process are closely correlative with the initial contact stage in the loading process. Furthermore, a mathematical model which is relative to the variation of contact force in loading is built, thus the physical mechanism of adhesion and principal factors of gold-plated materials are discussed. Finally, the physical process of molten bridge under the no mechanical contact situation is also analyzed in detail.

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 αarm_max, initial return spring's force Finiti_return_spring, normally closed (NC) contacts' force FNC_contacts, contacts' gap δgap, and normally opened (NO) contacts' over travel δNO_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.

There has been increasing demand to research the measuring method to characterize the batch consistency of contact rivets. An automated test equipment has been described that makes it possible to measure the electrical contact resistance with high efficiency. The relationship between contact force and contact resistance during the loading and unloading process was measured explicitly using AgPd alloy, stainless steel and sapphire substrate material with Au coatings as sphere indenters separately. To explain the phenomena of contact resistance decreasing more slowly than the traditional theoretical results during loading, the indenter with coating and rivet are modeled by using the commercial FEM software COMSOL Multiphysics. Besides the constriction resistance, the transition region Au coating resistance and the bulk resistance of the substrate are deduced from the simulated current lines profiles and iso-potentials. The difference of electrical conductivity between indenter material and gold coating is the reason for the occurrence of the transition region.

Bridge-type contacts are mainly used in high voltage direct current contactors for their performance of arc extinguishment and break capacity. It is also easy to add external magnetic field in them to blow the arc. Experiments on the arc behaviors were carried out when a copper bridge-type contact pair opening a 270V resistive circuit in the air. Influences of the shape of the movable contact, the opening speed and the magnetic flux density on the key behaviors, such as the arc duration, the arc re-ignition and the stability of arcing process, were investigated by using an oscilloscope and a high-speed camera. It was revealed that a uniform magnetic field with proper density could extinguish the arc stably and could reduce the arc re-ignition.

The micro-mechanism of molten pool and metal droplet sputtering are significant to the material erosion caused by breaking or making arcs especially for high-power switching devices. In this paper, based on Navier-Stokes equations for incompressible viscous fluid and potential equation for electric field, a 2D axially symmetric simplified hydrodynamic model was built to describe the formation of the molten metal droplet sputtering and molten pool under arc spot near electrode region. The melting process was considered by the relationship between melting metal volumetric percentage and temperature, a free surface of liquid metal deformation was solved by coupling moving mesh and the automatic re-meshing. The simulated metal droplet sputtering and molten pool behaviors are presented by the temperature and velocity distribution sequences. The influence mechanism of pressure distribution and heat flux on the formation of molten pool and metal droplet sputtering has been analyzed according to the temperature distribution and sputtering angles. Based on the simulation results, we can distinguish two different models of the molten metal droplet sputtering process: edge ejection and center ejection. Moreover, a new explanation is proposed based on calculated results with arc spot pressure distribution in the form of both unimodal and bimodal. It shows that the arc spot pressure distribution plays an important role in the metal droplet ejected from molten pool, the angle of the molten jet drop can be decreased along with the increment of the arc spot pressure.

An electrical arc is generated by opening the contacts of a relay when the current is above the minimum arc current in a circuit. A magneto-hydrodynamic (MHD) model was employed to simulate this dynamic arcing process. The distributions of arc parameters such as temperature, electrical field and magnetic flux density generated by opening the contacts in a circuit with a 5 A DC low current were obtained. The behaviors of the arc parameters with increasing gap length between the contacts were also simulated. The MHD model was then combined with structured dynamic layering, which is a dynamic meshing technique of computational fluid dynamics (CFD) to calculate the dynamic arcing process, and the arc parameters generated by opening the contacts in the circuit with a 5 A DC low current with a constant velocity were also obtained. It turned out that the computed time-varying contact voltage and arc duration agreed well with the test results. Thus, the validity of the simulation was demonstrated.

At present, during the design of sealed electromagnetic relay, the tolerances of design parameters are given with experience. The designer can't provide quantificational reliability index, and the blindness of tolerance distribution also causes unnecessary increase of machining cost. According to the study of electromagnetic force and spring force characteristics of a certain sealed electromagnetic relay with polarized magnetic system, this paper analyzed the influence of main design parameters' tolerances to the tolerance bands of electromagnetic force and spring force characteristics and achieved the strong correlative factors (viz. design parameters) that have obvious effect on tolerance bands of electromagnetic force and spring force characteristics. Then based on the calculation of reliability, the tolerance distribution method of key design parameters was given. This method not only can make the designed product satisfy requirement of reliability, but also reduce the machining cost.

To study the molten bridge phenomenon of contacts at the initial breaking process, an experimental device of molten bridge between slowly opening contacts was developed. The system consists of the contact moving control module, the circuit load and the observation module. The molten bridge of copper contact under two load conditions 9,V/19,A and 9,V/7.3,A were studied. The voltage and current characteristics curves of Cu molten bridge were extracted and the resistance and the instantaneous power of the molten bridge were analyzed. The image of the Cu molten bridge diameter was captured by CCD under 9,V/19,A and the influences of the contact force and the separation speed on the molten bridge length and the crater diameter of the anode were studied. The root profile of the Cu contacts after separation was analyzed by digital microscope. Research results show that the Cu molten bridge length has the same changing trend as the diameter of the anode crater. They both decrease with the increment of the separation speed and the decrement of the contact force.

High voltage DC contactors, for operation at voltage levels up to at least about 300,volts, find their increasing markets in applications such as electrical vehicles and aircrafts in which size and weight of cables are of extreme importance. The copper bridge-type contact, cooperated with magnetic field provided by permanent magnets and sealed in an arc chamber filled with high pressure gases, is a mainly used structure to interrupt the DC arc rapidly. Arc characteristic in different gases at different pressure varies greatly. This paper is focused on the arc characteristics of the bridge-type contact system when magnetic field is applied with nitrogen and gas at different pressure. The pressure of the gases varies from 1,atm to 2.5,atm. Arc characteristics, such as arc durations at different stages and arc motions in those gases are comparatively studied. The results are instructive for choosing the suitable arcing atmosphere in a DC bridge-type arc chamber of a contactor.

The reliability of electromagnetic relay (EMR) which contains a permanent magnet (PM) can be improved by a robust design method. In this parameter design process, the calculation of electromagnetic system is very important. In analytical calculation, PM is often equivalent to a lumped parameter model of one magnetic resistance and one magnetic potential, but significant error is often caused; in order to increase the accuracy, a distributed parameter calculation model (DPM) of PM bar is established; solution procedure as well as verification condition of this model is given; by a case study of the single PM bar, magnetic field lines division method is adopted to build the DPM, the starting point and section magnetic flux of each segment are solved, a comparison is made with finite element method (FEM) and measured data; the accuracy of this magnetic field line based distributed parameter model (MFDPM) in PM bar is verified; this model is applied to the electromagnetic system of a certain type EMR, electromagnetic system calculation model is established based on MFDPM, and the static force is calculated under different rotation angles; compared with traditional lumped parameter model and FEM, it proves to be of acceptable calculation accuracy and high calculation speed which fit the requirement of robust design.