2,808
edits
Changes
→6.1.1 Low and Medium Electrical Loads
Switching processes at low and medium electrical loads are experienced for example in relays and switches for the measuring technology, telecommunications, automotive usage, and appliances. The switching voltage ranges from μV to 400V with currents between μA and about 100A.
Guided by empirically developed arc-limiting graphs typical switching processes can be distinguished. As <xr id="fig:fig6.1"/>Fig. 6.1 illustrates, voltage and currentdetermine if switching occurs without arcing, results in a glow discharge, short instable arcs are generated, or a fully developed electrical arc is created. The more exact current-voltage curve characte-ristics are depending on the electrical contact material used. They also depend on the contact gap and the atmosphere the switching occurs in; an ambient air atmosphere is assumed in the shown schematic example.<figure id="fig:Arc-limiting graphs">
[[File:Arc-limiting graphs.jpg|right|thumb|Arc-limiting graphs (schematic) 1. Arc-less switching<br /> 2. Short instable arcs <br />3. Glow discharge <br />4. Full electrical arcs]]
</figure>
For the different requirements on the electrical contacts in various applications it is useful to differentiate across the broad spectrum of possible load conditions guided by the arc-limiting graphs between four different partial ranges which result in typical physical effects:
