Arc fault circuit interrupter, systems, apparatus and methods of detecting and interrupting electrical faults

• US 8,879,218 B2
• Filed: 12/18/2009
• Issued: 11/04/2014
• Est. Priority Date: 12/14/2007
• Status: Expired due to Fees

• Current Assignee: True-Safe Technologies, Inc.
• Original Assignee: True-Safe Technologies, Inc.
• Inventors: Tomimbang, Wendell E.
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): BROOKS, ANGELA D
• Application Number:
  US12/642,737
• Publication Number:
  US 20100097733A1
• Time in Patent Office: 1,782 Days
• Field of Search: None
• US Class Current: 361/42
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: H02H 1/0015 Using arc detectors

Abstract

In all electrical circuits, various arcing conditions can arise, however, the primary ones are series arcing (low current arcing), and, parallel arcing (high current arcing). An arc fault circuit interrupter (“AFCI”) that protects for both series and parallel arcing is called a combination type. An AFCI is a device that controls the effects of electrical arcing by opening a circuit through a tripping mechanism that isolates the load from the supply line upon detection of an arcing condition. In this invention, this arc fault is detected by a circuit employing a Hall-Effect sensor (“HES”) integrated circuit, and a microprocessor among other components.

Claims

1. An apparatus to detect electrical circuit faults comprising:

a microprocessor driven electronic circuit, said microprocessor being programed with software code to completely manage said electronic circuit, said microprocessor driven electronic circuit has a current sensor that is a power-driven and is a bi-directional Hall Effect Current Sensor Integrated Circuit comprising a Hall Current Drive with dynamic offset cancellation, gain and temperature coefficient adjustment, amplifiers, zero “

0”

current adjustment, analog and digital outputs, analog to digital converter, a ratio metric output voltage proportional to the current flow, stable output offset voltage and nearly zero magnetic hysteresis, said software code managed electronic circuit continuously monitoring a single or multi-phase AC, or DC, electrical circuit for fault conditions including series and parallel arcs, overcurrent, overload, short circuit, miswire, and end-of-life conditions, and said software code managed electronic circuit limiting the occurrence of nuisance tripping conditions while monitoring said electrical circuit for said faults, said microprocessor driven electronic circuit being assembled in a housing, said electronic circuit having line and load side terminals, said electronic circuit having an electromagnetic actuated circuit tripping contactor, a reset button, a test button, electronic circuit status visual indicators, electronic circuit fault detection audible indicators, and upon said code managed microprocessor driven electronic circuit'"'"'s detecting that one or more of said fault conditions exist, said code managed microprocessor driven electronic circuit then activates the electromagnetic contactor to trip open the electrical circuit and thereby isolate the monitored electrical circuit line and load connections.

2. The apparatus of claim 1, wherein the occurrence of nuissance tripping is limited through the implementation of algorithm-based code routines and selection of circuit components that filter noise and condition the line signal to insure accurate determination of real arcs and distinguish between real arcs from normal electrical load signatures that mimics that of an arc.

3. The apparatus of claim 1, wherein the detection of overload, overcurrent, and short circuit conditions are accomplished by algorithm-based code routines, comparing the output of the current sensor with established thresholds.

4. The apparatus of claim 1, wherein the housing is configured for electrical receptacles, receptacle outlets, circuit breakers, circuit switches, and electrical cords.

5. The apparatus of claim 1, wherein the electromagnetic contactor comprises a trip and reset mechanism using separate solenoid actuators which are independently driven by the trip and reset switching circuits through optically-coupled triacs or optocouplers.

6. The apparatus of claim 1, wherein the reset mechanism is manually-operated and the trip mechanism is solenoid-actuated through hardware and microprocessor code routines.

7. The apparatus of claim 1, wherein the electromagnetic contactor uses a single-solenoid actuator with reversible motion for trip and reset operations through hardware and microprocessor code routines, the reversibility being accomplished by alternately triggering the actuator in either the positive or negative slopes of the AC power supply signal.

8. The apparatus of claim 1, wherein the electromagnetic contactor utilizes a linear, single-motion, single-coil, solenoid actuator for its trip and reset functions by reversing positions with every stroke corresponding to a tripped or reset position through an integrated mechanical locking and displacement assembly.

9. The apparatus of claim 1, wherein the visual and audible indicators are used to annunciate device functions and conditions that include power on, fault condition, and the type of faults that occur including arc, overload, short circuit, miswire, and end-of-life.

10. The apparatus of claim 1, wherein the electronic circuit adopts to 60 hz and other fundamental frequencies by having the hardware timing configured for automatic response to line frequency changes determined through microprocessor code routines.

11. The apparatus of claim 1, wherein the output signals of said current sensor are conditioned by the anti-alias filter, buffer amplifier, and programmable gain amplifier for analysis and processing for detection of electrical faults including the presence of arcs by observing them in both the time and frequency domains.

12. The apparatus of claim 11, wherein a 4-pole butterworth filter is used as an anti-alias filter to prevent aliasing of sampled data and to remove noise in the signal.

13. The apparatus of claim 11, wherein the anti-alias filter causes a phase shift between the voltage signal to the Analog Comparator and the current signal to the Analog to Digital converter (ADC) where the variable threshold provided by the Digital to Analog Converter (DAC) for the analog comparator reference and capacitive elements added to the resistive divider compensate for the said phase shift, the digital to analog converter (DAC) reference signal being set as the high signal limit which is the power supply voltage of the microprocessor.

14. The apparatus of claim 11, wherein the programmable gain amplifier, being a low-drift instrumentation amplifier, maintains the amplitude of the output signal of the Hall Effect Current Sensor Integrated Circuit by auto-ranging or modifying the gain value based on signal levels within a range suitable for analog to digital conversion for the detection of arc and other electrical faults, connecting the low input to the low output and to the DC offset voltage allowing the AC component of the output signal from the Hall Effect Current Sensor Integrated Circuit to be amplified with variable gain while the DC component receives a constant gain.

15. The apparatus of claim 11, wherein the programmable gain amplifier is a microprocessor peripheral.

16. The apparatus of claim 11, wherein a buffer amplifier is used for attenuation and offset of the Hall Effect Current Sensor Integrated Circuit output, and provides the sampling reference and synchronization of the line signal to the output signal of the Hall Effect Current Sensor Integrated Circuit.

17. The apparatus of claim 11, wherein a resistive divider is used to attenuate and DC shift the line voltage at the output of the Current Sensor to match the input limits of the buffer amplifier which provides the reference signal to the analog comparator for positive feedback hysteresis to increase the slope of the reference at the instant of switching and thereby produce a more accurate synchronization of sampling to the AC line voltage.

18. The apparatus of claim 11, wherein the microprocessor comprises the peripherals to generate and process signals received from the Current Sensor and the power line, implement analog to digital data conversion, digital to analog data conversion, data comparison, switching and signaling functions to continuously monitor load conditions, and activate the switching and tripping mechanisms, the visual and audible indicators.

19. The apparatus of claim 1, wherein the microprocessor driven electronic circuit has a power supply that is a switch-mode-power-supply circuit operating at a defined range of input AC voltages with stable DC output to the power-driven components of the apparatus, same comprising an input rectifier and filter, a controller, a high frequency transformer, an output rectifier and filter, and integrated circuit power switcher.

20. The apparatus of claim 19, wherein the power supply circuit is linear.

21. The apparatus of claim 19, wherein the power supply circuit consists of two similar bridge rectifiers connected in parallel on the line and load sides of the electrical circuit to ensure uninterrupted power supply to the electrical circuit when a miswire fault condition occurs.

22. The apparatus of claim 21, wherein the power supply is a part of the apparatus'"'"' miswire protection circuitry.

23. The apparatus of claim 1, wherein the microprocessor is configured with a set of peripherals to perform sampling to support and generate the timing signal required for coherent Direct Fourier Transforms, use their properties to compute and detect arcs, and disengage the contacts when an arc occurs.

24. The apparatus of claim 1, wherein the electromagnetic contactor has a position sensing circuit connected on the load side of the electrical circuit and said sensing circuit determines the contactor position for miswire condition after the peak of the AC line sine wave where the contactor position changes and signal voltage on the load side is either existent or non-existent, according to the contactor position.

25. The apparatus of claim 1, wherein the microprocessor driven electronic circuit electrical circuit miswire fault monitoring protection circuitry utilizes an optocoupler as a test point to determine current flow from the electrical circuit line side of the electromagnetic contactor to the load side of the electrical circuit to detect a miswire condition and then feed back the signal to the microprocessor to initiate code routines to activate the visual indicators, audible indicator, and the electromagnetic contactor trip mechanism.

26. The apparatus of claim 1, wherein the microprocessor driven electronic circuit monitoring of end-of-life fault conditions are defined in its software code and determined through a series of routines and hardware test points as that condition when the apparatus is no longer able to perform its designed functions or unsafe to continue operation, or when the end of a pre-set time or cumulative operation time is reached as determined through a clock or time counter within the microprocessor, or the reset mechanism is unable to engage contacts between the line and load, or the test or trip mechanism is unable to disengage contacts between the line and load, or failure of a code routine to execute routines, the end-of-life being declared after the reset button is pressed but no longer able to reset the contacts.

27. The apparatus of claim 1, wherein the software code uses an infinite loop that starts only after the reset button is pressed to ensure accurate timing of the electromagnetic contactor opening and closing operations.

28. The apparatus of claim 1, wherein the test button sets the software code routine for a ARC DECLARE flag and introduces an arc value above the arc threshold into the data processing routine, enter the infinite loop and becomes interpreted as an arc and thereby go to the DECLAREARC routine to trip the contactor and isolate the line from the load side of the apparatus.

29. The apparatus of claim 1, wherein in the microprocessor'"'"'s software code the DeclareArc Flag is set upon decoding the switch and cannot be cleared by anything other than the reset button, the microprocessor reset function being inactive on end-of-life fault conditions including miswire fault.

30. The apparatus of claim 1, wherein in the microprocessor'"'"'s software code an infinite loop is the basis of the code which includes synchronization of sampling to AC line voltage, the electromagnetic contactor solenoid actuator switching, compute arc, miswire, end-of-life, compute gain, adjust gain, and declare arc;

the first action in the loop being TestArc flag, or DeclareArc Flag, or EndofLife flag, which alternatively could be in the end of the loop.

31. The apparatus of claim 1, wherein in the microprocessor'"'"'s software code the ratio of the amplitude of the 3^rd harmonic to the amplitude of the 2nd harmonic line signal multiplied by an arbitrary number is set as threshold for determining the occurrence of arcs which sets or clears the DeclareArc flag in the code routine.

32. The apparatus of claim 1, wherein the microprocessor driven electronic circuit'"'"'s synchronization of sampling to the AC line voltage is the basis for all its operations, where ADC sampling is on both the electrical circuit'"'"'s line current and line voltage sensor'"'"'s signals.

33. The apparatus of claim 1, wherein in the microprocessor'"'"'s software code a coherent Direct Fourier Transform (DFT) is used for processing sampled data including the DC (0^th harmonic), 2^nd and 3^rd harmonics in the detection of arcs, making possible the use of low-cost microprocessors and ensuring there is no spill-over between the frequency bins, thereby eliminating the need for windowing.

34. The apparatus of claim 1, wherein in the microprocessor'"'"'s software code the analog comparator interrupt service routine (ISR) differentiates between positive and negative slope zero-crossings where the main function is synchronized to the AC line positive slope zero-crossing provided by a variable which is set in the ISR to signal the main routine when this occurs, the analog comparator ISR driving the contactor solenoid switches when the appropriate flag is set to ensure that switching occurs at zero voltage to enhance the life of the electromagnetic contactor.

35. The apparatus of claim 1, wherein said software code managed electronic circuit also continuously monitors the electrical circuit for ground faults, and when a ground fault condition exists, said code managed microprocessor driven electronic circuit then activates the visual and audible indicators and the electromagnetic contactor to trip open the electrical circuit and thereby isolate the monitored electrical circuit line and load connections.

36. A method to detect electrical circuit faults comprising:

having a microprocessor driven electronic circuit, said microprocessor being programed with software code to completely manage said electronic circuit, said microprocessor driven electronic circuit has a current sensor that is a power-driven and is a bi-directional Hall Effect Current Sensor Integrated Circuit comprising a Hall Current Drive with dynamic offset cancellation, gain and temperature coefficient adjustment, amplifiers, zero “

0”

current adjustment, analog and digital outputs, analog to digital converter, a ratio metric output voltage proportional to the current flow, stable output offset voltage and nearly zero magnetic hysteresis, said software code managed electronic circuit continuously monitoring a single or multi-phase AC, or DC, electrical circuit for fault conditions including series and parallel arcs, overcurrent, overload, short circuit, miswire, and end-of-life conditions, and said software code managed electronic circuit limiting the occurrence of nuisance tripping conditions while monitoring said electrical circuit for said faults, said microprocessor driven electronic circuit being assembled in a housing, said electronic circuit having line and load side terminals, said electronic circuit having an electromagnetic actuated circuit tripping contactor, a reset button, a test button, electronic circuit status visual indicators, electronic circuit fault detection audible indicators, and upon said code managed microprocessor driven electronic circuit'"'"'s detecting that one or more of said fault conditions exist, said code managed microprocessor driven electronic circuit then activates the electromagnetic contactor to trip open the electrical circuit and thereby isolate the monitored electrical circuit line and load connections.