Static trip circuit breaker with automatic circuit trimming
AssigneeGeneral Electric Company
InventorGraham A. Scott
Life of this patent
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Abstract
Electronic trip units employed within static trip circuit breakers are individually calibrated and automatically adjusted to ensure that the trip transfer characteristics are within specification requirements. A trimming network within the trip unit circuit contains a plurality of parallel resistors each separately connected within the circuit by means of a fusible link. Test input and output values are compard to idealized values that are binary-weighted within a look-up table in the test equipment computer. The percent correction required is determined and the appropriate links are interrupted to provide ideal trip response.
Claims6
A method for calibrating a circuit breaker electronic trip unit comprising the steps of:
- providing a circuit breaker electronic trip unit containing a resistance network arranged as a plurality of trimming resistors electrically in parallel with a base resistor through a corresponding plurality of fusible links;
- applying a test input signal to said trip unit and reading a first pickup level output response;
- comparing said first pickup level output response to a predetermined pickup level and determining a first difference value;
- comparing said first difference value to predetermined binary weighted resistance values to provide a first calibration resistance value;
- and
- adjusting said resistance network within said trip unit to provide said first calibration resistance value to said trip unit.
Dependencies are inferred from the claim text.