PREDICTION OF THE DYNAMIC BEHAVIOUR OF ELECTROMAGNETIC RELAYS SUBMITTED TO MECHANICAL SHOCKS

摘要

During space flights, pyrotechnic devices are widely used to separate structural subsystems, to unfold solar panels or to activate propellant valves. The firing of these pyrotechnic devices generates severe shock waves (so-called pyroshocks) with high intensity and wide frequency range, which can damage the surrounding electronic equipment. Common observed damages more especially concern relay chatter and transfer, as well as failure of magnetic components. There is a lack of failure criteria for electronic equipment as well as computational techniques able to predict the dynamic behaviour of complex structures subjected to high frequency shock waves. The pyrotechnic shock behaviour is checked experimentally: test specifications imposed through embarked electronic devices are generally defined as a maximum limit imposed to the Shock Response Spectrum (SRS). This paper describes a methodology to check the electrical and mechanical behaviours of some electromagnetic relays submitted to severe mechanical shocks. Experimental results obtained when checking the perturbations induced by shocks on the electrical behaviour of some relays, such as the latching GP250 relay are also presented. Microswitches levels have been corre- lated with the magnitude and shape of different Shock Response Spectra. This paper presents also a simplified model of electromagnetic relays allowing to predict the electrical dysfunctions such as the micro-openings. The model has been updated using experimental frequency and modal analysis.