The method for detecting defects in movable armature of the signalling relay
Journal Title: Електромагнітна сумісність та безпека на залізничному транспорті - Year 2017, Vol 1, Issue 13
Abstract
Despite significant progress in the development of microelectronic rail automatic systems ob-served 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. Thus, signalling relays used for safety-critical or safety-related applications in railway signal-ling systems should be properly maintained and tested to ensure their performing safely and re-liably throughout their expected service life. With the purpose of developing a method for detecting defects in movable armature of the signalling relay, the time dependences of transient currents during relays switching have been investigated for relay in various technical conditions: in operable condition, as well as with arti-ficially created defects (bends) of contact springs. The measured data have been analyzed in the time and frequency domain using the wavelet transform modifications (CWT, DWT, DWPT). The analysis of the transient currents was carried out using segmentation of the current char-acteristics of the relay. The relay transient current at first and third segments which corresponded to unmovable anchor state, increase with time during relay switch-on approximately as the expo-nential function. The time constants of the relay current were calculated by approximating the measured cur-rent-time dependences at the first segment of the current curve by exponential function. The presence of defects in the movable armature of the relay had practically no effect on the values of calculated time constants. However, these values strongly depended on the technical condition of the relay magnetic circuit and the relay coil, as well as on the voltage applied to the coil terminals. This behavior of the relay time constant on the first segment of the relay current characteristic makes it possible to use this parameter to monitor the technical state of the electromagnetic relay system. Defects of the armature and contact springs led to the appearance of additional features at the second segment of the relay transient current, which corresponded to the movement of the arma-ture. The magnitude of these features on the current curve depended on the value of bending of the relay's contact spring. The width and appearance time of the features at the second segment of the current-switching curve correspond to the non-simultaneous switching of the relay con-tacts. To determine the amplitude (energy) of these features (peaks) on transient current curve, their duration and the times of appearance, the wavelet transform was used. The results of inves-tigations confirmed the possibility of determining the defects of the relay movable armature by using wavelet analysis of the second segment of the relay transient current characteristic.
Authors and Affiliations
V. Havriliuk
Keywords
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