Study of the Reliability of the Switching-On Process of LV Relays Powered by Distorted AC Supply Source

The article presents research on the reliability of the switching-on process of electromagnetically actuated alternating current (AC) low voltage relays powered by distorted voltage waveforms. The aim of the research was to assess the influence of the nature and level of supply source distortions on particular switching-on time-related parameters. A measurement stand and software developed for the purposes of the experiments allowed for recognizing the impact of particular factors describing dynamics of the switching-on process. During tests, driving coils of relays were powered through the various AC voltage waveforms characterized by similar total harmonic distortion (THD) values that were applied at different phases of voltage waveform. Performed laboratory measurements showed the various impact of individual parameters (RMS value, shape, harmonic content, THD factor) on the reliability of the switching-on operation, e.g., switching time, contact loss, connection reliability. The carried-out analysis indicated the main factors and their impact level upon the reliability of the switching-on process.