Communications: electrical – Condition responsive indicating system – With particular system function
Reexamination Certificate
2002-07-16
2004-04-13
Pope, Daryl (Department: 2632)
Communications: electrical
Condition responsive indicating system
With particular system function
C340S635000, C340S644000, C340S003430, C200S05200R, C324S415000, C324S500000, C324S509000
Reexamination Certificate
active
06720872
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to circuit interrupters and, more particularly, to ground fault/arc fault circuit interrupters. The invention also relates to methods of testing ground fault/arc fault circuit interrupters.
2. Background Information
During the early 1970's, people protecting ground fault circuit interrupters were introduced to provide protection against electrocution.
Today, people protecting ground fault circuit interrupters include both circuit breakers and receptacles. These devices are covered by Underwriters Laboratory (UL) Standard UL 943. The Standard UL 943 requires that a ground fault circuit interrupter (GFCI) device include a built-in test circuit including a test button, which allows a user to periodically test the device. When the test button is depressed, a simulated ground fault current is produced that causes the GFCI device to open if such device is operating properly. The device must be manually reset, in order to be returned to service. Otherwise, if the GFCI device has failed, then the device will not open in response to the test button.
Today, a ground fault receptacle employs two buttons, TEST and RESET. See, for example, U.S. Pat. No. 4,595,894.
Recently, a GFCI receptacle employing a “lockout” test procedure has been introduced. See U.S. Pat. Nos. 6,381,112; and 6,040,967. In this GFCI receptacle, the button labeled TEST simply manually opens the receptacle by freeing a spring charged trip mechanism, rather than by producing an artificial ground test current. The GFCI receptacle opens regardless whether it is functional. The actual test is performed when the RESET button is pushed. During this process, an artificial ground test current is generated and the trip spring is charged. If the GFCI receptacle passes the test, then the trip latch mechanism moves to a position such that when the RESET button is released, the spring is latched in the charged position and the contacts of the GFCI receptacle close. Otherwise, if the GFCI receptacle trip circuit is inoperable, then the spring is not latched and the contacts remain open. In this manner, if the GFCI receptacle fails the test, then it is unable to apply power to the protected circuit. See, for example, U.S. Pat. Nos. 6,309,248; 6,288,882; 6,282,070; 6,246,558; and 6,040,967.
An arc fault circuit interrupter (AFCI) provides protection against hazardous electrical arcing. UL Standard UL 1699 covers conformance testing of these devices and requires a mechanism to test the AFCI device via a TEST button as is required for a GFCI receptacle. In the case of the AFCI device, the test waveform simulates an arc fault. The Standard UL 1699 contemplates that someday a device (e.g., circuit breaker; receptacle) would be developed that meets both the requirements of a GFCI device and an AFCI device in a single package. In this case, the Standard UL 1699 requires that both functions be tested independently.
Some AFCI/GFCI circuit breakers may employ a first test button for an arc fault test and a second test button for a ground fault test. See, for example, U.S. Pat. No. 5,459,630.
U.S. patent application Ser. No. 09/069,355, filed Apr. 29, 1998, discloses a miniature circuit breaker with a common rocker button which is rotated in one direction to actuate the ground fault test circuit, and the opposite direction to actuate the arc fault test circuit. See, also, U.S. Pat. Nos. 6,215,378; and 6,285,534.
U.S. Pat. No. 5,982,593 discloses a circuit breaker including a ground fault test circuit for testing a ground fault detector trip mechanism, and an arc fault test circuit for testing an arc fault detector trip mechanism. A state machine circuit responsive to a single test push button automatically sequentially tests both of the ground fault and arc fault detector trip mechanisms.
The wiring device industry has spent years educating the consumer on the purpose and function of the two buttons labeled TEST and RESET on a GFCI device that, otherwise, looks like a conventional receptacle.
There is room for improvement in circuit interrupters, such as GFCI/AFCI devices.
SUMMARY OF THE INVENTION
In the case of a combined GFCI/AFCI circuit interrupter, such as a receptacle, it is desirable to retain the two-button TEST/RESET paradigm, while adding a new test for the AFCI function. It is desired, therefore, to retain only two buttons (i.e., TEST and RESET) for a GFCI/AFCI receptacle, while performing three functions, namely: an arc fault test, a ground fault test, and a mechanical reset of the receptacle.
As one aspect of the invention, a method of testing a circuit interrupter comprises engaging a test button; opening separable contacts responsive to the step of engaging the test button; testing an arc fault protection circuit responsive to the step of engaging the test button; engaging a reset button; testing a ground fault protection circuit responsive to the step of engaging the reset button; and closing the separable contacts responsive to successfully testing at least one of the arc fault protection circuit and the ground fault protection circuit.
The method may comprise energizing a trip coil responsive to successfully testing the arc fault protection circuit; and opening the separable contacts responsive to the step of energizing the trip coil.
The method may comprise activating an indicator responsive to successfully testing the arc fault protection circuit; and closing the separable contacts responsive to successfully testing the ground fault protection circuit.
The method may comprise closing the separable contacts responsive to successfully testing both of the arc fault protection circuit and the ground fault protection circuit.
Power may be removed from the ground fault protection circuit responsive to unsuccessfully testing the arc fault protection circuit.
As another aspect of the invention, a circuit interrupter for a power circuit comprises: a first terminal; a second terminal; separable contacts electrically connected between the first terminal and the second terminal; an operating mechanism for opening the separable contacts, the operating mechanism having a closed position for closing the separable contacts; a trip mechanism cooperating with the operating mechanism to trip open the separable contacts; a ground fault protection circuit operatively associated with the power circuit; an arc fault protection circuit operatively associated with the power circuit; a test button; a reset button; and means for testing the ground fault protection circuit, testing the arc fault protection circuit, and restoring the operating mechanism to the closed position responsive to sequential activation of the test button and the reset button.
The reset button may have an engaged position, and the means for testing includes a ground fault test circuit producing a ground fault test current for the ground fault protection circuit responsive to the engaged position of the reset button. The reset button may further have an disengaged position. The trip mechanism may include a trip solenoid. The ground fault protection circuit may energize the trip solenoid after a successful test of the ground fault protection circuit with the ground fault test current. The operating mechanism may move to the closed position responsive to the reset button moving from the engaged position to the disengaged position in order to close the separable contacts.
The means for testing may include means for restoring the operating mechanism to the closed position to close the separable contacts after successful test of both of the ground fault protection circuit and the arc fault protection circuit.
The means for testing may include means for indicating a successful test of the arc fault protection circuit.
As another aspect of the invention, a method of testing a circuit interrupter comprises the steps of: engaging a test button; opening separable contacts responsive to the step of engaging the test button; testing a first fault protection circuit responsive to the step of engaging the test bu
Elms Robert T.
Engel Joseph C.
Schlotterer John C.
Eaton Corporation
Moran Martin J.
Pope Daryl
LandOfFree
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