Moving parts / Mechanical indicator
Some power relays have a mechanical indicator fitted. The indicator is connected to the armature. actuator or contact springs to show the actual switching position of the contacts. Mechanical indicators, therefore. indicate the actual switching state, whereas electrical indicators. such as LEDs. only indicate that voltage is applied to the coil terminals.
Depending on the circuit. this may not give information as to the actual switching state of the relay. e.g. in case of a broken coil.
Mechanical system / Wear and tear
Movement of parts within the relay, like the armature, actuator, mechanical indicator and contacts will cause wear,which may in turn lead to changes in the operational characteristics of the relay (such as pull in voltage).
In addition, the generation of particles caused by the rubbing motion of these parts can affect contact reliability.
When using sealed relays for switching medium to high loads with a high level of arcing. corrosion may result. The combination of NQ generated by the arc and water vapour absorbed from the ambient humidity forms highly corrosive nitric acid inside the relay. Accelerated corrosion of the intemal metal parts such as the yoke, amiature and contact springs may adversely affect reliable operation of the relay.
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