Arc fault detector and method

• US 7,009,406 B2
• Filed: 04/23/2004
• Issued: 03/07/2006
• Est. Priority Date: 04/24/2003
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (Aptiv PLC)
• Original Assignee: Delphi Technologies, Inc. (Aptiv PLC)
• Inventors: Naidu, Malakondaiah, Gopalakrishnan, Suresh, Schoepf, Thomas J.
• Primary Examiner(s): Nguyen, Vincent Q.
• Application Number:
  US10/831,733
• Publication Number:
  US 20040263183A1
• Time in Patent Office: 683 Days
• Field of Search: 324/536, 324/539, 324520-522, 324541-544, 340/647, 340/657, 340/658, 361/42, 361/90, 702/58
• US Class Current: 324/536
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities

Abstract

The present invention discloses an arc fault detector including a shunt resistor deployed in a circuit being protected, an arc discriminator sensing voltages across the shunt resistor and outputting an arc detection signal when it detects current variations caused by parallel and series arc faults, a signal transformer buffering the arc detection signal and outputting a pulse, a switch transient detector detecting a voltage differential across load switches and outputting a pulsed switch transient detection signal when the voltage differential across load switches exceeds a reference value, a line interrupter such as a static relay, a switch controller including logic gates generating a trip signal based on predetermined criteria, and a manual switch for resetting the line interrupter. A second embodiment of the present invention senses voltage induced in a coil wrapped around a toroidal core to detect current variations in conductors which pass through the center of the toroidal core.

Claims

1. An arc fault detector for a circuit comprising:

a current shunt resistor coupled in series with said circuit; and

an arc discriminator comprising an amplifier sensing a first voltage on a first side of said current shunt resistor, sensing a second voltage on a second side of said current shunt resistor, and producing a first signal proportional to a current flow through said current shunt resistor, said arc discriminator further comprising a change detector receiving said first signal as input and producing an arc fault detection signal as output when said change detector detects a change in said first signal indicative of a presence of an arc fault in said circuit;

wherein said change detector comprises a first splitter receiving said first signal as input and providing a second and a third signal as outputs, a delay circuit receiving said second signal as input and producing a delayed signal having a predetermined delay as output, a reference circuit receiving said third signal as input and producing a reference signal as output, and a comparator receiving said delayed signal and said reference signal as inputs, and producing said arc fault detection signal as an output when a difference between said reference signal and said delay signal satisfies a predetermined criteria.

2. The arc fault detector as recited in claim 1 wherein said delay circuit comprises an R-C circuit.

3. The arc fault detector as recited in claim 1 wherein said delay circuit comprises a low pass filter.

4. The arc fault detector as recited in claim 3 wherein said reference circuit comprises an amplifier.

5. The arc fault detector as recited in claim 4 wherein said first splitter comprises a buffer.

6. The arc fault detector as recited in claim 1, wherein said change detector comprises a series arc detector and a parallel arc detector.

7. An arc fault detector for a circuit comprising:

a current shunt resistor coupled in series with said circuit; and

an arc discriminator comprising an amplifier sensing a first voltage on a first side of said current shunt resistor, sensing a second voltage on a second side of said current shunt resistor, and producing a first signal proportional to a current flow through said current shunt resistor, said arc discriminator further comprising a change detector receiving said first signal as input and producing an arc fault detection signal as output when said change detector detects a change in said first signal indicative of a presence of an arc fault in said circuit;

wherein said change detector comprises a first buffer having an input coupled to said amplifier, said first buffer having a first and second output;

a delay circuit coupled to said first output of said first buffer, said delay circuit providing a delayed signal as an output;

a reference circuit coupled to said second output of said first buffer, said reference circuit providing a reference signal as an output;

a first comparator having a first input coupled to said delay circuit and a second input coupled to said reference circuit, wherein said first comparator is configured to provide a series arc detection signal only when there is a decrease in voltage of said first signal which thereby causes the voltage of said reference signal to be less than said voltage of said delayed signal; and

a logic gate having a first input coupled to said first comparator, said logic gate being configured to generate said arc fault detection signal as an output when said series arc fault detection signal is detected by said first input.

8. An arc fault detector for a circuit comprising:

a current shunt resistor coupled in series with said circuit; and

an arc discriminator comprising an amplifier sensing a first voltage on a first side of said current shunt resistor, sensing a second voltage on a second side of said current shunt resistor, and producing a first signal proportional to a current flow through said current shunt resistor, said arc discriminator further comprising a change detector receiving said first signal as input and producing an arc fault detection signal as output when said change detector detects a change in said first signal indicative of a presence of an arc fault in said circuit;

wherein said change detector comprises a first buffer having an input coupled with said amplifier, said first buffer having a first and second output;

a delay circuit coupled to said first output of said second buffer, said delay circuit providing a delayed signal as an output;

a reference circuit coupled to said second output of said first buffer, said reference circuit providing a reference signal as an output;

a second comparator having a first input coupled to said delay circuit and a second input coupled to said reference circuit, wherein said second comparator is configured to provide a parallel arc detection signal only when there is a increase in voltage of said first signal which thereby causes the voltage of said reference signal to be greater than said voltage of said delayed signal; and

a logic gate having a second input coupled to said second comparator, said logic gate being configured to generate said arc fault detection signal as an output when said parallel arc fault detection signal is detected by said second input.

9. A method of detecting an arc fault in a circuit comprising:

coupling a current shunt resistor in said circuit;

monitoring a voltage differential across said current shunt resistor;

detecting a change in said voltage differential;

comparing said change to at least one threshold; and

generating a signal when said change exceeds said at least one threshold;

wherein said step of monitoring comprises sensing a first voltage on a first side of said current shunt resistor and sensing a second voltage on a second side of said current shunt resistor,

wherein said change is proportional to a current flow through said current shunt resistor; and

wherein said threshold is indicative of a presence of an arc fault in said circuit.