The article deals with the issue of electromagnetic disturbances caused by electromechanical relays. Electromagnetic compatibility (EMC) is important for the reliable work of electrical and electronic devices. Our research focused on the low-voltage relay, which is the source of electrical fast transients (EFT)/burst disturbances. The voltage and current waveforms were tested on the constructed stand while opening the relays’ contacts. We investigated one-circuit topology with varied element parameters in order to observe their influence on the burst phenomenon. The new technologies in the measurement equipment allow us to observe many detailed aspects of the burst phenomenon, which were not reported up to now. In order to analyze the disturbances, they have been fragmented into restoration, ignition and arc times. The number of disturbance cycles differs depending on the value of the circuit capacitance on the load side. The effect of capacity on times of restoration, ignition and burning arc was also observed. The division into cycles allowed us to observe changes in the studied phenomenon along with the increased distance between the relay contacts during its opening. There were also discrepancies between the presentation of the phenomenon in the standard defining the method of measuring the resistance to interference EFT/burst and the measurement results.

The electric arc is a very complex phenomenon, therefore numerical modeling is not an easy issue. The aim of this article is to present the phenomenon known as showering arc and to compare the results obtained during laboratory measurements with simulations using ready-made element offered in the program Matlab Simulink. This phenomenon is based on a rapid ignition and extinguishing of the electric arc between the relay contacts when opening them. The effect of this phenomenon are electromagnetic disturbances, the maximum voltage of which might be many times greater than the nominal voltage. For this reason, these disturbances may cause malfunctioning electronic devices or lead to its damage.