Solid-state trip unit of an electrical circuit breaker with contact wear indicator
AssigneeMerlin Gerin
InventorsLuc Weynachter, Vincent Corcoles
Life of this patent
Estimating the term…
Abstract
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 value 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.
Claims7
A digital solid-state trip unit including an electrical circuit breaker with separable contacts, comprising:
- detection circuit means for generating an analog signal proportional to current flowing in a conductor protected by the circuit breaker;
- analog-to-digital convertor means, connected to said detection circuit means, for converting said analog signal into a sampled digitized signal;
- digital processing means connected to said analog-to-digital convertor means and generating a tripping order after at least one of a long time delay and short time delay when said sampled digitized signal exceeds respective predetermined thresholds, said tripping order being time delayed as a function of a magnitude of said sampled digitized signal;
- means, responsive to said tripping order, for opening said separable contact;
- said digital processing means comprising:
- means for detecting a maximum value of current broken each time said separable contacts open by comparison between the successive values of said digitized signals which are applied to said processing means between the time the circuit breaker tripping order is generated and effective opening of the contacts occur;
- means for generating, upon each opening of said separable contacts, a wear value representative of wear of said separable contacts as a function of a respective said maximum value of current;
- means for calculating a sum of a succession of said wear values generated from a succession of said contact openings;
- means for storing said sum in a memory;
- and
- means for displaying said sum to provide an indication of a degree of wear of said contacts.
Dependencies are inferred from the claim text.