Solid-state trip unit of an electrical circuit breaker with contact wear indicator

Abstract From the Canadian patent

A digital solid-state trip unit of an electrical circuit breaker is equipped with an electrical contact wear indicator enabling the degree of wear of these contacts to be known. Each time the circuit breaker performs a break, the microprocessor determines a contact wear value, in terms of the maximum valve of the current broken. The correspondence between the wear value and the current broken is stored in a ROM memory and the successive wear values are added in a NOVRAM memory whose contents are representative of the degree of contact wear. These contents can be displayed to indicate to the user that the condition of the contacts has to be checked.