Sigma Instruments, Inc.

Joseph R Thibodeau

Thomas Yeh

John J Powers

Matthew G Dillon

An inrush restraint in a fault indicator disables trip in response to the current in the cable being monitored changing from reset to trip values within a predetermined period.

Fault indicator with inrush restraint

A faulted circuit indicator includes an inrush restraint circuit that suppresses a trip signal when an inrush current rises from below a minimum value to a trip value within a predetermined time and then drops again to another value such as the trip value. According to various aspects the restraint ends after a fixed time or after a variable time. According to another aspect a second trip circuit overrides the inrush restraint circuit when the current rises a given amount beyond the first trip value.

Faulted current indicators and inrush restraints therefor

The reset circuit of a fault indicator is coupled to a transformer secondary winding by a cable having an elongated conductor and a resistance close to the secondary winding. The resistance is capable of withstanding a minimum transient impulse of 10 kv.

Fault indicating means

In the device disclosed, a load is energized from energy-carrying lines. A detector responsive to a cyclically recurring physical condition, such as daylight, places a switch either in an operating mode or an idling mode in response to the absence of the condition. A control shifts from an idling mode to an operating mode in response to the detector being in a given one of its modes and shifts back to the idling mode after a given time less than the period of the cyclically recurring physical condition. A circuit responds to the control being shifted to its operating mode in response to the given one of the modes of the detector and responds to the detector simultaneously being in the operating mode so as to connect the lines to the load.

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Dedham, MA, United States of America

Joseph R Thibodeau