Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Reexamination Certificate
2000-08-04
2004-01-13
Tso, Edward H. (Department: 2838)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
Reexamination Certificate
active
06678137
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to arc fault current interrupting (AFCI) circuit breakers. More specifically, the present invention relates to a temperature compensation circuit for an AFCI breaker.
AFCI circuit breakers are well known. These breakers comprise contacts that open upon sensing arcing from line to ground, or from line to neutral. Arc fault current breakers typically use a differential transformer to measure arcing from line to ground. Detecting arcing from line to neutral is accomplished by detecting rapid changes in load current by measuring voltage drop across a relatively constant resistance, usually a bi-metallic strip within the circuit breaker. Tripping of the AFCI breaker occurs when a predetermined number of arcs above a certain current level are detected within a predetermined time.
One characteristic of the bimetal element found in an AFCI breaker is that its resistance decreases as the ambient temperature decreases. It can be appreciated that the effect of the above characteristic is that the voltage developed across the bimetal element decreases with temperature for a given current. Typically, the electronic sensing circuitry in an arc fault current interrupting (AFCI) breaker is designed to have a fixed gain within a range of operating temperatures. Because the gain is fixed, low current arcs measured at low temperatures will develop a voltage that is interpreted to be below a certain threshold and will not be counted as “arcs”. In other words, because the bimetal element caused a loss of gain as a result of temperature characteristics, the arcs or voltage developed across the bimetal element is made insufficient to count as an “arc”. The result is that the number “arcs”, or the number of voltages that are below a predetermined current threshold are reduced along with the sensitivity of the AFCI breaker to the occurrence of arc faults.
Schemes for an increase in overall gain are known. This approach typically solves problems related to inadequate gain at low temperatures. However, nuisance tripping is increased at room and higher temperatures. To offset the increased gain and prevent nuisance tripping, changes to decrease the response to low frequencies can be made. Arc faults typically cause a signal that is high frequency in nature, whereas noise is typically low frequency in nature. This approach works to reduce nuisance tripping, however, arc faults can cause a signal that has a low frequency. Therefore, changes to decrease the response to low frequencies can reduce the sensitivity of the circuit breaker to some arc faults. In sum, a trade off between gain, frequency response, and temperature is difficult to make.
BRIEF SUMMERY OF THE INVENTION
In an embodiment of the present invention, a temperature compensation circuit is used for an arc fault current interrupting circuit breaker. The arc fault current interrupting circuit breaker is configured to stop a flow of electrical current to a portion of an electrical distribution circuit. The temperature compensation circuit includes a low pass filter configured to receive a signal indicative of a voltage in the electrical distribution circuit. The low pass filter includes an input resistance configured to receive the signal. The input resistance has a positive temperature coefficient. The low pass filter also includes an operational amplifier having a first input and an output, the first input is electrically connected to the input resistance. A feedback resistance is electrically connected to the first input and to an output of the operational amplifier, and a feedback capacitance electrically connected to the first input and to an output of the operational amplifier.
In an alternative embodiment, the feedback resistance has a negative temperature coefficient. In yet another embodiment, both the input resistance has a positive temperature coefficient, and the feedback resistance has a negative temperature coefficient.
REFERENCES:
patent: 3401363 (1968-09-01), Vyskocil et al.
patent: 3443258 (1969-05-01), Dunham et al.
patent: 3596218 (1971-07-01), Layton
patent: 3596219 (1971-07-01), Erickson
patent: 4208690 (1980-06-01), McGinnis et al.
patent: 4345288 (1982-08-01), Kampf et al.
patent: 4466071 (1984-08-01), Russell, Jr.
patent: 4513268 (1985-04-01), Seymour et al.
patent: 4513342 (1985-04-01), Rocha
patent: 4552018 (1985-11-01), Legatti et al.
patent: 4573259 (1986-03-01), Seymour et al.
patent: 4589052 (1986-05-01), Dougherty
patent: 4598183 (1986-07-01), Gardner et al.
patent: 4636910 (1987-01-01), Chadwick
patent: 4641216 (1987-02-01), Morris et al.
patent: 4641217 (1987-02-01), Morris et al.
patent: 4658322 (1987-04-01), Rivera
patent: 4667263 (1987-05-01), Morris et al.
patent: 4672501 (1987-06-01), Bilac et al.
patent: 4686600 (1987-08-01), Morris et al.
patent: 4688134 (1987-08-01), Freeman et al.
patent: 4702002 (1987-10-01), Morris et al.
patent: 4847850 (1989-07-01), Kafka et al.
patent: 4878143 (1989-10-01), Kalal et al.
patent: 4878144 (1989-10-01), Nebon
patent: 4931894 (1990-06-01), Legatti
patent: 4936894 (1990-06-01), Larson et al.
patent: 5089796 (1992-02-01), Glennon et al.
patent: 5121282 (1992-06-01), White
patent: 5166887 (1992-11-01), Farrington et al.
patent: 5185684 (1993-02-01), Beihoff et al.
patent: 5185685 (1993-02-01), Tennies et al.
patent: 5185686 (1993-02-01), Hansen et al.
patent: 5185687 (1993-02-01), Beihoff et al.
patent: 5206596 (1993-04-01), Beihoff et al.
patent: 5208542 (1993-05-01), Tennies et al.
patent: 5223682 (1993-06-01), Pham et al.
patent: 5224006 (1993-06-01), MacKenzie et al.
patent: 5229730 (1993-07-01), Legatti et al.
patent: 5245302 (1993-09-01), Brune et al.
patent: 5245498 (1993-09-01), Uchida et al.
patent: 5250918 (1993-10-01), Edds et al.
patent: 5299730 (1994-04-01), Pasch et al.
patent: 5303113 (1994-04-01), Goleman et al.
patent: 5307230 (1994-04-01), MacKenzie
patent: 5359293 (1994-10-01), Boksiner et al.
patent: 5418463 (1995-05-01), Fleming et al.
patent: 5420740 (1995-05-01), MacKenzie et al.
patent: 5432455 (1995-07-01), Blades
patent: 5434509 (1995-07-01), Blades
patent: 5452223 (1995-09-01), Zuercher et al.
patent: 5453723 (1995-09-01), Fello et al.
patent: 5459630 (1995-10-01), MacKenzie et al.
patent: 5475609 (1995-12-01), Apothaker
patent: 5483211 (1996-01-01), Carrodus et al.
patent: 5485093 (1996-01-01), Russell et al.
patent: 5493278 (1996-02-01), MacKenzie et al.
patent: 5506789 (1996-04-01), Russell et al.
patent: 5510946 (1996-04-01), Franklin
patent: 5510949 (1996-04-01), Innes
patent: 5512832 (1996-04-01), Russell et al.
patent: 5519561 (1996-05-01), Mrenna et al.
patent: 5546266 (1996-08-01), MacKenzie et al.
patent: 5550751 (1996-08-01), Russell
patent: 5561605 (1996-10-01), Zuercher et al.
patent: 5578931 (1996-11-01), Russell et al.
patent: 5583732 (1996-12-01), Seymour et al.
patent: 5590012 (1996-12-01), Dollar, II
patent: 5600526 (1997-02-01), Russell et al.
patent: 5614878 (1997-03-01), Patrick et al.
patent: 5615075 (1997-03-01), Kim
patent: 5629824 (1997-05-01), Rankin et al.
patent: 5659453 (1997-08-01), Russell et al.
patent: 5694101 (1997-12-01), Lavelle et al.
patent: 5706154 (1998-01-01), Seymour
patent: 5774319 (1998-06-01), Carter et al.
patent: 5805397 (1998-09-01), MacKenzie
patent: 5818671 (1998-10-01), Seymour et al.
patent: 5831500 (1998-11-01), Turner et al.
patent: 5939991 (1999-08-01), Deng
patent: 5940256 (1999-08-01), Mackenzie et al.
patent: 6057997 (2000-05-01), Mackenzie et al.
patent: 6128169 (2000-10-01), Neiger et al.
patent: 6259340 (2001-07-01), Fuhr et al.
patent: 6331763 (2001-12-01), Thomas et al.
patent: 6477021 (2002-11-01), Haun et al.
patent: 2036032 (1991-08-01), None
patent: WO 91/13454 (1991-09-01), None
patent: WO 95/20235 (1995-07-01), None
Mason, Jr. Henry H.
Tilghman Douglas B.
Cantor Colburn lLP
General Electric Company
Tibbits Pia
Tso Edward H.
LandOfFree
Temperature compensation circuit for an arc fault current... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature compensation circuit for an arc fault current..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature compensation circuit for an arc fault current... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3253948