US 5,181,155 A · Overcurrent trip circuit

Abstract

An overcurrent trip circuit monitors the rate of rise of the current and the magnitude of the current in a power conductor and opens a circuit containing the power conductor when either the rate of rise of the current exceeds a first preselected limit value or the magnitude of the current exceeds a second preselected limit value. The inherent inductance in a metering shunt is used to produce a voltage signal that contains a component which is representative of the rate of change of current in a power conductor. This voltage signal is compared to a first reference signal to produce a trip signal when the voltage exceeds the first reference signal. In addition, the voltage signal is processed and the processed voltage signal is compared to a second reference signal to produce a second trip signal when the magnitude of the processed voltage signal exceeds the magnitude of the second reference signal. The power circuit is then opened in response to either of the first or second trip signals.

Claims7

Dependent claims

An overcurrent trip circuit comprising:

means for producing a status signal representative of current and rate of rise of the current in a power conductor, said means for producing a status signal including a shunt sensor inline with said power conductor, said shunt sensor having a resistive component for use in producing that portion of said status signal that is representative of said current in said power conductor and further having an inductive component for use in producing that portion of said status signal that is representative of said rate of rise of the current in said power conductor;
means for comparing said status signal to a first reference signal representative of a first preselected limit value for the rate of rise of current in said power conductor, and for producing a first trip signal when the magnitude of said status signal exceeds the magnitude of said first reference signal;
means for processing said status signal to produce a processed status signal, said processed status signal representative of an average value of the current through said power conductor;
means for comparing said processed status signal to a second reference signal and for producing a second trip signal when the magnitude of said processed status signal exceeds the magnitude of said second reference signal;
and
means for opening a circuit in response to said first or second trip signals.

3 more elements

Dependencies are inferred from the claim text.

Overcurrent trip circuit

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Overcurrent trip circuit

Life of this patent

Abstract

Claims7