Arc fault circuit interrupter and method for disabling series arc protection during current transients

• US 7,359,168 B2
• Filed: 10/18/2005
• Issued: 04/15/2008
• Est. Priority Date: 10/18/2005
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Elms, Robert T., Parker, Kevin L.
• Primary Examiner(s): Sherry; Michael
• Assistant Examiner(s): THOMAS, LUCY M
• Application Number:
  US11/253,193
• Publication Number:
  US 20070086124A1
• Time in Patent Office: 910 Days
• Field of Search: 702/58, 361/42, 361/44
• US Class Current: 361/42
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 1/043 to inrush currents H02H1/046 takes precedence; differential protection of transformers H02H7/045

Abstract

An arc fault circuit interrupter includes a line terminal, a load terminal, separable contacts electrically connected between the line terminal and the load terminal, and a current sensor structured to sense current associated with the load and flowing between the line terminal and the load terminal and through the separable contacts. The sensed current includes a plurality of line cycles. An arc fault detection circuit is structured to provide series arc protection and to generate a trip signal responsive to the sensed current from the current sensor. The arc fault detection circuit collects a plurality of samples of the sensed current over the line cycles, determines a single current transient associated with energization of the load, and responsively inhibits the series arc protection. An operating mechanism is structured to open the separable contacts responsive to the trip signal.

Claims

1. An arc fault circuit interrupter for an electrical circuit including a load, said arc fault circuit interrupter comprising:

a line terminal;

a load terminal;

separable contacts electrically connected between said line terminal and said load terminal;

a current sensor structured to sense current associated with said load and flowing between said line terminal and said load terminal and through said separable contacts, said sensed current including a plurality of line cycles;

at least one arc fault detection circuit structured to provide series arc protection and to generate a trip signal responsive to said sensed current from said current sensor, one of said at least one arc fault detection circuit being structured to collect a plurality of samples of said sensed current over said line cycles, determine a single current transient associated with energization of said load, and responsively inhibit said series arc protection;

an operating mechanism structured to open said separable contacts responsive to said trip signal;

wherein said one of said at least one arc fault detection circuit is further structured to determine a first maximum value of said sensed current from one of said line cycles and a second maximum value of said sensed current from the subsequent one of said line cycles, determine if the difference between said first and second maximum values is greater than a first predetermined value and responsively set a first variable to a second predetermined value, and responsively increment a second variable by a third predetermined value; and

wherein said one of said at least one arc fault detection circuit is further structured, for each of said line cycles, to determine if the first variable is greater than zero and to responsively decrement said first variable by a predetermined value.

2. An arc fault circuit interrupter for an electrical circuit including a load, said arc fault circuit interrupter comprising:

a line terminal;

a load terminal;

separable contacts electrically connected between said line terminal and said load terminal;

a current sensor structured to sense current associated with said load and flowing between said line terminal and said load terminal and through said separable contacts, said sensed current including a plurality of line cycles;

at least one arc fault detection circuit structured to provide series arc protection and to generate a trip signal responsive to said sensed current from said current sensor, one of said at least one arc fault detection circuit being structured to collect a plurality of samples of said sensed current over said line cycles, determine a single current transient associated with energization of said load, and responsively inhibit said series arc protection;

an operating mechanism structured to open said separable contacts responsive to said trip signal;

wherein said one of said at least one arc fault detection circuit is further structured to determine a first maximum value of said sensed current from one of said line cycles and a second maximum value of said sensed current from the subsequent one of said line cycles, determine if the difference between said first and second maximum values is greater than a first predetermined value and responsively set a first variable to a second predetermined value, and responsively increment a second variable by a third predetermined value; and

wherein said one of said at least one arc fault detection circuit is further structured, for each of said line cycles, to determine if the second variable is greater than zero and to responsively decrement said second variable by a predetermined value.

3. A method of enabling or disabling series arc protection for an electrical circuit including a load, said method comprising:

providing series arc protection for said electrical circuit;

sensing current associated with said load and flowing in said electrical circuit, said sensed current including a plurality of line cycles;

collecting a plurality of samples of said sensed current over said line cycles;

determining a single current transient associated with energization of said load, responsively inhibiting said providing series arc protection;

further comprising

determining a first maximum value of said sensed current from one of said line cycles and a second maximum value of said sensed current from the subsequent one of said line cycles;

determining if the difference between said first and second maximum values is greater than a first predetermined value and responsively setting a first variable to a second predetermined value, and responsively incrementing a second variable by a third predetermined value; and

further comprising

for each of said line cycles, determining if the first variable is greater than zero and responsively decrementing said first variable by a predetermined value.

4. A method of enabling or disabling series arc protection for an electrical circuit including a load, said method comprising:

providing series arc protection for said electrical circuit;

sensing current associated with said load and flowing in said electrical circuit, said sensed current including a plurality of line cycles;

collecting a plurality of samples of said sensed current over said line cycles;

determining a single current transient associated with energization of said load, responsively inhibiting said providing series arc protection;

further comprising

determining a first maximum value of said sensed current from one of said line cycles and a second maximum value of said sensed current from the subsequent one of said line cycles;

determining if the difference between said first and second maximum values is greater than a first predetermined value and responsively setting a first variable to a second predetermined value, and responsively incrementing a second variable by a third predetermined value; and

further comprising

for each of said line cycles, determining if the second variable is greater than zero and responsively decrementing said second variable by a predetermined value.