Self-calibrating overcurrent detector
AssigneeInternational Business Machines Corporation
InventorAnthony J. Rice
Life of this patent
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Abstract
Circuit for detecting a fault current in an installation where the load (RL) varies. Total current (IS) is converted into a voltage (VS). During an initialization cycle, means such as counter (9), digital-to-analog converter (10), comparator (5), resistors (R1, R2) generate a voltage (VS) equal to VS at the end of the initialization cycle, and a threshold voltage VS=kVS. During operation, voltage VS is compared with threshold VD in order to provide a fault detection indication which is transmitted to the protection circuit by a logic circuit, that is, AND gate (17) and OR gate (19). During the initialization cycle, protection is obtained by comparing VS with a reference voltage in a comparator (7). This device is used to protect machines having an expandable configuration.
Claims10
Self-calibrating overcurrent detector characterized in that it includes:
- means for generating a first voltage (VS) which is proportional to the current whose fault value is to be detected,
- means which are active during an initialization cycle for generating a second increasing voltage (VC) which, at the end of the initialization cycle, is equal to the first voltage and for deriving from said second voltage a threshold voltage (VD) such that VS=kVC, k being a numerical factor higher than 1, and
- first means for comparing the threshold voltage with the first voltage in order to provide a fault detection indication after the initialization cycle.
Dependencies are inferred from the claim text.