Modelling of the Dynamic Behaviour of Electromechanical Relays for the Analysis of Sensitivity to Shocks and Vibrations

Abstract

During their operating life, electromechanical relays (EMRs) are subjected to external mechanical vibrations that can induce undesirable vibratory responses in the movable part of the relay and thus produce an unwanted temporary break in electric connections. This paper presents a simplified multiphysics model dedicated to the prediction of the maximum vibration levels that these relays can undergo before a loss of contact occurs. Our methodology considers the magnetic aspects as well as the mechanical aspects. The dynamic behaviour of the movable part is modelled as a cantilever beam subjected at its extremity to an elastic force. The dynamic parameters were updated from the identification of the first natural modes of the movable part of the relay. The magnetic force acting on the movable part was computed using a one-dimensional approach with an equivalent magnetic circuit and was corroborated thanks to experimental measurements and two-dimensional Finite Element simulations. The interaction between the electromagnetic and mechanical phenomena was taken into account using a parameterization coupled approach. Our methodology has been applied to the study of the PED PXC-1203 relay. The numerical predictions were validated using experimental data measured in the frequency range [2][3][4][5][6][7][8]. A parametric analysis of our model was performed and shows the influence of some factors, like the air gap and the rated voltage, that affect the performance of the relay under external mechanical vibrations.

A New Model of Electromechanical Relays for Predicting the Motion and Electromagnetic Dynamics

“…Substituting (10) in (2), and solving the system of (1) and (2), the explicit equation for the dynamics of the magnetic flux is finally obtained.…”

“…Now, if angular position θ 1 is known, (11) can be solved by numerical integration and then the current through the coil is directly obtained by using (2) and (10). In addition, inductance L of the coil can also be calculated by means of (10) and considering that L = N 2 / .…”

“…Some works combining the two methods can also be found. See, e.g., the research in [9], where a MEC-based model is improved by using a correction factor calculated from FEM simulations, or [10], where an one-dimensional MEC model and a two-dimensional FEM analysis are compared. On the other hand, pure FEM-based models have been proposed, e.g., for calculating the attractive torque of a permanent-magnet relay [11].…”

“…A mechanical model based on the Euler-Bernoulli theory for beams is proposed to predict the motion of a relay in [12], where a viscoelastic spring-damper model is also presented for explaining the contact bounces. The beam theory is used in other researches [10], but the most widespread approach is the use of rigid-body models with rectilinear motions and a single degree of freedom [4], [7], [8].…”

The method for detecting defects in movable armature of the signalling relay

“…Despite significant progress in the development of microelectronic rail automatic systems observed in recent decades, relay-contact devices are still widely used in railway signalling systems, that are fundamental to the safe operation of railways and must perform predictably and reliably [1][2][3][4][5][6]. Thus, signalling relays used for safety-critical or safety-related applications in railway signalling systems should be properly maintained and tested to ensure their performing safely and reliably throughout their expected service life.…”