Huimin Liang

Mechanical and Electrical Characteristics of the Electromagnetic Relay under Vibration and Shock Environment

The electromagnetic relay, which has mechanical structure and break/make contacts, is affected by vibration and shock environment greatly. Contact wear and failure will be result from serious mechanical conditions. The samples used in this study were relays consisting two spring sets connected with armature component. Simulation results for a variety of vibration levels, frequencies, and shock levels are presented. Thereafter main factors and threshold conditions which influencing contact reliability were determined by the modal analysis and the harmonic response analysis and transient response analysis. The vibration and shock characteristics of movable parts within relay were also obtained by using high speed camera PhantomV7.3�ƒ 10000fps�≈ , thus the mechanism of contact failure is revealed clearly. In addition, the characteristics of contact resistance were investigated when relay working in the mechanical environment. The results are valuable in modeling characteristics degradation and contact failure evaluation caused by mechanical environment for electromagnetic relay. structure. Zhai (3) studied the natural frequency and vibration reaction force of reed by using the analytical method and the finite element program ANSYS/LS-DYNA individually. In his research, the limit vibration acceleration of spring system, referring to the maximum of vibration acceleration which can keep the spring contact reliable, is presented. The results are valuable in determining the thresholds of vibration condition for electromagnetic relay. The other relative research on testing and analyzing performance for relay that working in the mechanical vibration environment were so few, except Flowers (4-7) investigated the electrical connector fretting behavior induced by vibration. We have ever designed the vibration characteristics testing and analyzing system specialized for electromagnetic relay (8). In this paper, simulation model of some commercial electromagnetic relay was built by using FEA software MSC.Patran/Nastran, subsequently modal analysis and harmonic analysis and transient analysis induced by vibration and shock were completed. Experiment results agreed with simulation results well, so the threshold conditions that keep the spring contact reliable was determined. At last the effect of vibration and shock condition on contact resistance of relay is also investigated.

Thermal Analysis of Sealed Electromagnetic Relays Using 3-D Finite Element Method

Up to now, it is difficult to test the inner temperatures of sealed electromagnetic relays. In this paper, the temperature distribution of a sealed electromagnetic relay is obtained by using 3-D finite element analysis. The quality of thermal simulation results depends on the accuracy of both the modeled heat sources and heat sinks. Due to the high performance requirements of sealed electromagnetic relay it is interesting to know not only the temperatures of the conducting parts but also the thermal impact on the plastic components. Therefore, the non-metallic parts of the sealed electromagnetic relay (including the air within the device) are now part of the model. In order to improve the accuracy of simulation, the contact radius is calculated in advance. The relationship between convection heat transfer coefficient and temperature and how to consider connecting wires boundary condition are also researched here. Finally, the temperature distribution of a sealed electromagnetic relay is obtained by this method. Comparisons with experimental results confirm its validity.

A New Automated Test Equipment for Measuring Electrical Contact Resistance of Real Size Rivets

It is well known that electrical contact resistance influencing factors include not only the contact material physical characteristics, contact type (sphere-flat, flat-flat), the contact surface status (clean, contaminated), but also contact current and mechanical load during measuring. Electrical contact material industry has considerable trouble with batch consistency check of rivet contacts. An automated test equipment and a test method have been described that make it possible to measure the electrical contact resistance of many real size rivet-type contacts with shank diameters 1~4mm at small contact loads with high efficiency. A stainless steel hemisphere with gold coating is designed as standard indenter; meanwhile the alternative choice would be the sphere-flat, flat-flat and sphere-sphere rivet contact pairs. Firstly, the voltage vs. current characteristics of AgCdO rivets is tested under different constant contact force. Secondly, the relationship between contact load and contact resistance during loading and unloading is investigated explicitly with different current. Furthermore, the effect of surface roughness and cleanness on the contact resistance is analyzed by comparison with normal and polished rivets, and those of long term exposure to the air. This equipment can be used for finding out the contact resistance consistency of batch contacts effectively for statistics analysis. But it also helps for the research work on the affecting factors of electrical contact resistance of stationary contacts.

Thermal Stability Analysis of Disconnect Switch Based on FEM

Working performance of disconnect switch is affected by maximum permissible temperature exceeding which is caused by the heat loss of resistance. 2-D finite element analysis model of disconnect switch is established. It is used for electrical-thermal coupled field simulation analysis for ensuring its safety and reliability. Firstly, the contact depth and contact radius of disconnect switch in the closed state is calculated. Then, steady-state temperature rise and transient temperature rise of the disconnect switch are simulated. The average temperature rise, temperature distribution and contact temperature versus time curve are presented. Based on the results of simulation, which are compared with the experimental results, thermal stability is analyzed. The analysis result is of academic and practical value for reliability design of disconnect switch.

Method for Identification of Nonlinear Parameters and Its Application to Data Analysis for Aerospace Relay Reliability

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.

Structure classification of electromagnetic relays and comparison of typical magnetic system containing permanent magnet

The electromagnetic relays have lots of structures and are applied widely in the automation control system in aerospace. Firstly, the structures of aerospace electromagnetic relays (AEMR) were classified. According to the structure arrangement, there are three layers, two layers and one layer structures; from electromagnetic system, there are clapper type, balance armature type, polarized magnetic system and balance force magnetic system; from armature returning mode, there are spring returning, permanent magnet returning, permanent magnet magnetic circuit returning and polarized magnetic circuit returning modes. All of these structures were compared separately. Then, the equivalent magnetic circuit model of the typical polarized magnetic system and balance force magnetic system are founded. The ultimate difference between these magnetic systems was illuminated based on the polarized magnetic system criterion. The research conclusions can be used to direct the design of AEMR.

Steady Temperature Rise Analysis of Non Segregated Phase Bus Based on Finite Element Method

In the design and analysis of Non Segregated Phase Bus (NSPB), steady temperature rise calculation is very important especially for the bolt-joint contact structure NSPB. In order to ensure the safety of such products, taking a certain type of NSPB for example, finite element method (FEM) calculation model of NSPB is built based on thermal transfer theory, the maximum temperature rise of NSPB is calculated under different DC and AC loads within the bus working range, the temperature distribution of contact area is simulated; and the temperature correspondence relationship of DC-AC is discussed; the NSPB temperature rise has been tested and compared with the experiment results, the validity of NSPB FEM calculation is verified.

A Type of Attractive Force Calculation Model of Polarized Relay Based on Nonlinear Permanent Magnet Bar Subsection Model

In polarized relay, the armatures are sometimes made of permanent magnet (PM). The attractive force calculation is very important in the design and analysis of polarized relays. For some polarized relays which use less expensive permanent magnet bars that have nonlinear magnetic properties, the modeling of such nonlinear permanent magnet (NPM) bars is particularly important to the design of relay contact force, operation speeds and subsequent effects on switching performances. In this paper, an Equivalent Magnetic Calculation model of a NPM polarized relay is built based on a subsection model. The subsection interfaces of NPM are analyzed and the leakage permeance between the armature and yoke is calculated. Then the electromagnetic force is calculated on various rotation positions. This is compared with a finite element method (FEM) and the accuracy of the subsection calculation model is verified.

Research on the Starting Points of the Combined Subsection Permanent Magnet

One of the important parts for the polarized magnetic system design is the equivalent processing of the permanent magnet (PM) in polarized relay, which affects the design accuracy of the system directly. Based on the combined subsection permanent magnet (CSPM) in the condition of the open magnetic circuit, this paper concludes that the starting points of PM are different, by setting up the equivalent magnetic circuit, and analyzing the relationship between the starting points of PM in theory. Meanwhile, it provides the method of solving the starting points. Finally, the conclusion is validated by the analysis example.