A qualitative analysis on the effect of external vibrations on the performance of relays

When using relays in stationary devices which are exposed to external vibrations due to, say, a nearby electrical machine, the relay is in addition loaded with external mechanical vibrations of different amplitudes and frequencies. These additional loads cause periodical oscillations to all nonmovable and movable parts within the relay which in turn result into a change of start-off and release currents of the relay, hence affecting the protective capability of the relay. This paper gives a qualitative analysis of the change of the relay capability. The start-off time is found to decrease due to a periodical decrease of the working gap in the magnetic system and a decrease in frictional coefficient in the bearings and the pusher, while the release current increases due to the periodical increase of the armature load.