Method and apparatus for determining the wear on a contact element

An electronic unit for an electrical switch, the electronic unit comprising:

• a value input module for obtaining electrical values which represent a variable, which is relevant to the power flowing through the switch during a switching operation, as a function of time;
• and
• a wear determination module having a computation unit and a non-transitory data memory having an executable program recorded thereon for execution by the computation unit, wherein the program comprises:
• a plurality of wear contribution calculation rules (fi) for calculating respective wear contribution values from respective subsets (I(ti);
• I([ti;t′i])) of the recorded electrical values, wherein at least two of the wear contribution calculation rules (fi) differ from one another,
• a wear value calculation routine for calculating a wear value (d), which represents the wear on a contact element, from the wear contribution values, and
• a percentage wear calculation routine, which comprises:
• calculating, based on the calculated wear value, a percentage wear of the contact element of the electrical switch, as a proportion of a maximum wear value that the calculated wear value constitutes;
• determining whether the calculated percentage wear is greater than a predefined warning threshold value;
• and
• outputting a command to block operation of the electrical switch when the calculated percentage wear is determined to be greater than the predefined warning threshold value.