Self-calibrating overcurrent detector
First Claim
1. 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, andfirst means for comparing the threshold voltage with the first voltage in order to provide a fault detection indication after the initialization cycle.
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Accused Products
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.
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Citations
10 Claims
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1. Self-calibrating overcurrent detector characterized in that it includes:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification