Intelligent life testing methods and apparatus for leakage current protection

This application claims priority of Chinese Patent Application No. 2005 1073 2772.1, filed on Dec. 26, 2005, entitled “Intelligent Life Testing Methods and Apparatus for Leakage Current Protection” by Wusheng CHEN, Fu WANG, and Lianyun WANG, the disclosure of which is incorporated herein by reference in its entirety.

This application is related to four co-pending U.S. patent applications, entitled “Intelligent Life Testing Methods and Apparatus for Leakage Current Protection Device with Indicating Means,” by Feng ZHANG, Honigliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG; “Apparatus and Methods for Testing the Life of a Leakage Current Protection Device,” by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG; “Intelligent Life Testing Methods and Apparatus for Leakage Current Protection,” by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG; and “Intelligent Life Testing Methods and Apparatus for Leakage Current Protection,” by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG, respectively. The above identified co-pending applications were filed on the same day that this application was filed, and with the same assignee as that of this application. The disclosures of the above identified co-pending applications are incorporated herein by reference in their entireties.

The present invention generally relates to a leakage current protection device, and more particularly, to an apparatus and methods for intelligently testing the life of a leakage current protection device.

Leakage current protection can be divided into two categories according to their functionalities: ground fault circuit interrupter (hereinafter “GFCI”) and arc fault circuit interrupter (hereinafter “AFCI”). In order to achieve the goal of leakage current protection, a leakage current protection device used for appliances comprises at least two components: a trip mechanism and a leakage current detection circuit. The trip mechanism comprises a silicon controlled rectifier (hereinafter “SCR”), trip coil, and trip circuit interrupter device. The leakage current detection circuit comprises induction coils, a signal amplifier and a controller.

The operating principle of a GFCI used for appliances is as follows. In a normal condition, the electric current on a hot wire of an electrical socket should be the same as the electric current on a neutral wire in the same electrical socket. When a leakage current occurs, there exists a current differential between the hot wire and the neutral wire of the electrical socket. The inductive coil of the leakage current protection device monitors the current differential and transfers the current differential into a voltage signal. The voltage signal is then amplified by the signal amplifier and sent to the controller. If the current differential exceeds a predetermined threshold, the controller sends a control signal to the trip circuit interrupter to cut off the connection between the AC power and the appliance to prevent damage caused by the leakage current.

For an AFCI used for appliances, in a normal condition, the electric current on a hot wire of an electrical socket should be the same as the electric current on a neutral wire in the same electrical socket, and the variation of both the electric current is same. When an arc fault occurs due to aging or damages of the AFCI device, the current or voltage between the hot wire and the neutral wire of the electrical socket exhibits a series of repeated pulse signals. The inductive coil of the arc fault protection device detects the pulse signals and converts the pulse signals to a voltage signal. The voltage signal is amplified by the signal amplifier and sent to the controller. If the amplitude of the pulse signals or the their occurring frequency exceed certain predetermined threshold, the controller sends a control signal to the trip circuit interrupter to cut off the connection between the AC power and the appliance to prevent further damage caused by the arc fault.

Leakage current protection devices have been widespreadly used because of their superior performance. However, the leakage protection devices may fail to provide such leakage current protection, if they are installed improperly and/or they are damaged due to aging. If a faulty controller can not output a correct control signal, or a trip mechanism fails to cut off the connection between the AC power and the appliance, the leakage current protection device will not be able to provide the leakage current protection, which may cause further damages or accidents. Although most leakage current protection devices are equipped with a manual testing button, usually, users seldom use the manual testing button. Therefore, the leakage current protection devices need an additional circuit to automatically detect malfunctions, faults or the end of the life of such devices. The great relevance would be gained if a leakage current protection device is capable of automatically detecting a fault therein or its end of the life, and consequently alerting a user to take an appropriate action including repairing or replacing the leakage current detection circuit.

Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.

In one aspect, the present invention relates to an apparatus for testing the life of a leakage current protection device. The leakage current protection device has a first inductive coil N 1 , a second inductive coil N 2 , a first input, a second input, a first output electrically coupled to the second input through the first inductive coil N 1 and the second inductive coil N 2 , a second output, a third output, a trip switch SW 101 having two LINE terminals and electrically coupled to the first input and the second input, respectively, for receiving an AC power, and two LOAD terminals and electrically coupled to the inputs of an electrical appliance, respectively, a power supply circuit having an input electrically coupled to the first input, and an output electrically coupled to the second output, a trip coil circuit having a switching device VD 1 having a gate, an anode and a cathode, an input, an output electrically coupled to the third output, and a leakage current detection circuit having an output electrically coupled to the input of the trip coil circuit, and a power supply input, electrically coupled to the output of the power supply circuit and the second output.

In one embodiment, the apparatus includes a trip mechanism state generator having a first input electrically coupled to the third output of the leakage current protection device, a second input electrically coupled to the first input of the leakage current protection device, a third input electrically coupled to the second input of the leakage current protection device, a first output and a second output. The trip mechanism state generator is adapted for generating a trip mechanism state at the first output and the second output, where the trip mechanism state has a first state and a second state. When the trip mechanism state is in the first state, there is no fault exist in the leakage current protection device. When the trip mechanism state is in the second state, there is at least one fault exists in the leakage current protection device.

In one embodiment, the trip mechanism state generator has: a first diode D 1 having a cathode and an anode electrically coupled to the second input of the trip mechanism state generator; a second diode D 2 having a cathode electrically coupled to the cathode of the first diode D 1 and the first input of the trip mechanism state generator, and an anode electrically coupled to the third input of the trip mechanism state generator; a third diode D 3 having an anode and a cathode electrically coupled to the second input of the leakage current protection device and the anode of the second diode D 2 ; a fourth diode D 4 having a cathode electrically coupled to the anode of the first diode D 1 and the first input of the leakage current protection device, and an anode electrically coupled to a first output of the trip mechanism state generator; a fifth resistor R 5 having a first terminal electrically coupled to the first output of the trip mechanism state generator, and a second terminal electrically coupled to the second output; and a sixth resistor R 6 having a first terminal electrically coupled to the second terminal of the fifth resistor R 5 and the second output of the trip mechanism state generator, and a second terminal electrically coupled to the anode of the third diode D 3 .

The apparatus also includes a fault alarm generator having a first input electrically coupled to the first output of the trip mechanism state generator, a second input electrically coupled to the second output of the trip mechanism state generator, and a power supply input electrically coupled to the second output of the leakage current protection device.

In one embodiment, the fault alarm circuit has a multi-vibrator having a light emitting diode (LED) D 8 . The multi-vibrator generates no vibration indicating that there is no fault in the leakage current protection device when the fault alarm circuit receives a negative DC voltage, while the multi-vibrator generates vibrations and a visible alarm through the LED D 8 indicating that there is at least one fault in the leakage current protection device when the fault alarm circuit receives a positive DC voltage. In one embodiment, the fault alarm circuit comprises an audio alarm circuit for generating an audible alarm.

The apparatus further includes a ground fault simulation unit having an input electrically coupled to the first input of the leakage current protection device, and an output electrically coupled to the first output of the leakage current protection device.

In one embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and a second terminal; a second resistor R 2 having a first terminal and a second terminal; a third resistor R 3 having a first terminal and a second terminal; a seventh diode D 7 having a cathode and an anode, wherein the anode of the seventh diode D 7 is connected to the input that is electrically coupled a hot wire of the AC power, and the cathode of the seventh diode D 7 is connected to both the first terminal of the resistor R 1 and the first terminal of the second resistor R 2 ; a first transistor Q 1 having a first collector electrically coupled to the second terminal of the first resistor R 1 , a first emitter electrically coupled to both the second terminal of the third resistor R 3 and the output, and a first base; and a sixth zener diode D 6 having an anode electrically coupled to the base of the first transistor Q 1 , and a cathode electrically coupled to both the second terminal of the second resistor R 2 and the first terminal of the third resistor R 3 .

In another embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and a second terminal; a second resistor R 2 having a first terminal and a second terminal; a third resistor R 3 having a first terminal and a second terminal electrically coupled to the second output 2 ; a seventh diode D 7 having an anode electrically coupled to the input of the ground fault simulation unit, and a cathode electrically coupled to both the first terminal of the first resistor R 1 and the first terminal of the second resistor R 2 ; a first transistor Q 1 having a first collector electrically coupled to the second terminal of the first resistor R 1 , a first emitter electrically coupled to the second input of the leakage current protection device, and a base; and a sixth zener diode D 6 having an anode electrically coupled to the base of the first transistor Q 1 , and a cathode electrically coupled to both the second terminal of the second resistor R 2 and the first terminal of the third resistor R 3 .

In yet another embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and a second terminal; a seventh diode D 7 having an anode electrically coupled to the input, and a cathode electrically coupled to the first terminal of the resistor R 1 ; and a transformer T 1 having a primary winding having a first primary terminal P 1 and a second primary terminal P 2 , and a secondary winding having a first secondary terminal S 1 and a second secondary terminal S 2 , wherein the first primary terminal P 1 is electrically coupled to the second terminal of the first resistor R 1 , the second primary terminal P 2 is electrically coupled to the second input of the leakage current protection device, the first secondary terminal S 1 is electrically coupled to the second secondary terminal S 2 through the first inductive coil N 1 and the second inductive coil N 2 .

In an alternative embodiment, the ground fault simulation unit has: a seventh diode D 7 having a cathode and an anode electrically coupled to the input; and a first resistor R 1 having a first terminal electrically coupled to the cathode of the seventh diode D 7 , and a second terminal electrically coupled to the output.

In yet an alternative embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and second terminal; a seventh diode D 7 having an anode electrically coupled to the input, and a cathode electrically coupled to the first terminal of the first resistor R 1 ; and a sixth zener diode D 6 having a cathode electrically coupled to the second terminal of the first resistor R 1 , and an anode electrically coupled to the output.

In operation, the ground fault simulation unit generates a simulated ground fault signal during every positive half-wave of the AC power, the simulated ground fault signal is detected by the leakage current detection circuit, the leakage current detection circuit responsively generates a signal to turn the switching device VD 1 into its conductive state so as to allow a current to pass therethrough, the passed current is converted into a DC voltage in accordance with a trip mechanism state generated by the trip mechanism state generator, the fault alarm circuit receives and analyzes the DC voltage and indicates whether a fault exists in the leakage current protection device. In one embodiment, the DC voltage is detected at the first terminal and the second terminal of the resistor R 5 of the trip mechanism state generator. The DC voltage is a negative voltage if there is no fault in the leakage current protection device, and wherein the DC voltage is a positive voltage if there is at least one fault in the leakage current protection device.

In another aspect, the present invention relates to a method for intelligently testing the life of a leakage current protection device. The leakage current protection device has a first inductive coil N 1 , a second inductive coil N 2 , a first input, a second input, a first output electrically coupled to the second input through the first inductive coil N 1 and the second inductive coil N 2 , a second output, a third output, a trip switch SW 101 having two LINE terminals and electrically coupled to the first input and the second input, respectively, for receiving an AC power, and two LOAD terminals and electrically coupled to the inputs of an electrical appliance, respectively, a power supply circuit having an input electrically coupled to the first input, and an output electrically coupled to the second output, a trip coil circuit having a switching device VD 1 having a gate, an anode and a cathode, an input, an output electrically coupled to the third output, and a leakage current detection circuit having an output electrically coupled to the input of the trip coil circuit, and a power supply inputp electrically coupled to the output of the power supply circuit and the second output.

In one embodiment, the method includes the step of providing a testing device having a trip mechanism state generator having a first input electrically coupled to the third output of the leakage current protection device, a second input electrically coupled to the first input of the leakage current protection device, a third input electrically coupled to the second input of the leakage current protection device, a first output and a second output, wherein the trip mechanism state generator is adapted for generating a trip mechanism state at the first output and the second output, wherein the trip mechanism state has a first state and a second state; a fault alarm generator having a first input electrically coupled to the first output of the trip mechanism state generator, a second input electrically coupled to the second output of the trip mechanism state generator, and a power supply input electrically coupled to the second output of the leakage current protection device; and a ground fault simulation unit having an input electrically coupled to the first input of the leakage current protection device, and an output electrically coupled to the first output of the leakage current protection device.

The method further includes the steps of generating a simulated ground fault signal during every positive half-wave of the AC power by the ground fault simulation unit; detecting the simulated ground fault signal at the leakage current detection circuit; generating a signal to turn the switching device VD 1 into its conductive state so as to allow a current to pass therethrough; generating a DC voltage in responsive to a trip mechanism state at the trip mechanism state generator, wherein the trip mechanism state is in a first state that there is no fault exist in the leakage current protection device, or in a second state that there is at least one fault exists in the leakage current protection device; receiving the DC voltage at the fault alarm circuit; and indicating whether at least one fault exists in the leakage current protection device. In one embodiment, the indicating step includes the step of producing a visible alarm and/or an audible alarm.

In yet another aspect, the present invention relates to an apparatus for life testing. In one embodiment, the apparatus has a leakage current protection device having a first inductive coil N 1 , a second inductive coil N 2 , a first input, a second input, a first output electrically coupled to the second input through the first inductive coil N 1 and the second inductive coil N 2 , a second output, a third output, a trip switch SW 101 having two LINE terminals and electrically coupled to the first input and the second input, respectively, for receiving an AC power, and two LOAD terminals and electrically coupled to the inputs of an electrical appliance, respectively, a power supply circuit having an input electrically coupled to the first input, and an output electrically coupled to the second output, a trip coil circuit having a switching device VD 1 having a gate, an anode and a cathode, an input, an output electrically coupled to the third output, and a leakage current detection circuit having an output electrically coupled to the input of the trip coil circuit, and a power supply inputp electrically coupled to the output of the power supply circuit and the second output

Furthermore, the apparatus includes a trip mechanism state generator having a first input electrically coupled to the third output of the leakage current protection device, a second input electrically coupled to the first input of the leakage current protection device, a third input electrically coupled to the second input of the leakage current protection device, a first output and a second output. The trip mechanism state generator is adapted for generating a trip mechanism state at the first output and the second output, where the trip mechanism state has a first state and a second state. When the trip mechanism state is in the first state, there is no fault exist in the leakage current protection device. When the trip mechanism state is in the second state, there is at least one fault exists in the leakage current protection device.

Moreover, the apparatus also includes a fault alarm generator having a first input electrically coupled to the first output of the trip mechanism state generator, a second input electrically coupled to the second output of the trip mechanism state generator, and a power supply input electrically coupled to the second output of the leakage current protection device.

Additionally, the apparatus further includes a ground fault simulation unit having an input electrically coupled to the first input of the leakage current protection device, and an output electrically coupled to the first output of the leakage current protection device.

In operation, the ground fault simulation unit generates a simulated ground fault signal during every positive half-wave of the AC power, the simulated ground fault signal is detected by the leakage current detection circuit, the leakage current detection circuit responsively generates a signal to turn the switching device VD 1 into its conductive state so as to allow a current to pass therethrough, the passed current is converted into a DC voltage in accordance with a trip mechanism state generated by the trip mechanism state generator, the fault alarm circuit receives and analyzes the DC voltage and indicates whether a fault exists in the leakage current protection device.

In one embodiment, the trip mechanism state generator has: a first diode D 1 having a cathode and an anode electrically coupled to the second input of the trip mechanism state generator; a second diode D 2 having a cathode electrically coupled to the cathode of the first diode D 1 and the first input of the trip mechanism state generator, and an anode electrically coupled to the third input of the trip mechanism state generator; a third diode D 3 having an anode and a cathode electrically coupled to the second input of the leakage current protection device and the anode of the second diode D 2 ; a fourth diode D 4 having a cathode electrically coupled to the anode of the first diode D 1 and the first input of the leakage current protection device, and an anode electrically coupled to a first output of the trip mechanism state generator; a fifth resistor R 5 having a first terminal electrically coupled to the first output of the trip mechanism state generator, and a second terminal electrically coupled to the second output; and a sixth resistor R 6 having a first terminal electrically coupled to the second terminal of the fifth resistor R 5 and the second output of the trip mechanism state generator, and a second terminal electrically coupled to the anode of the third diode D 3 . In one embodiment, the DC voltage is detected at the first terminal and the second terminal of the resistor R 5 . The DC voltage is a negative voltage if there is no fault in the leakage current protection device, and wherein the DC voltage is a positive voltage if there is at least one fault in the leakage current protection device.

In one embodiment, the fault alarm circuit has a multi-vibrator having a light emitting diode (LED) D 8 . The multi-vibrator generates no vibration indicating that there is no fault in the leakage current protection device when the fault alarm circuit receives a negative DC voltage, while the multi-vibrator generates vibrations and a visible alarm through the LED D 8 indicating that there is at least one fault in the leakage current protection device when the fault alarm circuit receives a positive DC voltage. In one embodiment, the fault alarm circuit comprises an audio alarm circuit for generating an audible alarm.

In one embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and a second terminal; a second resistor R 2 having a first terminal and a second terminal; a third resistor R 3 having a first terminal and a second terminal; a seventh diode D 7 having a cathode and an anode, wherein the anode of the seventh diode D 7 is connected to the input that is electrically coupled a hot wire of the AC power, and the cathode of the seventh diode D 7 is connected to both the first terminal of the resistor R 1 and the first terminal of the second resistor R 2 ; a first transistor Q 1 having a first collector electrically coupled to the second terminal of the first resistor R 1 , a first emitter electrically coupled to both the second terminal of the third resistor R 3 and the output, and a first base; and a sixth zener diode D 6 having an anode electrically coupled to the base of the first transistor Q 1 , and a cathode electrically coupled to both the second terminal of the second resistor R 2 and the first terminal of the third resistor R 3 .

In another embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and a second terminal; a second resistor R 2 having a first terminal and a second terminal; a third resistor R 3 having a first terminal and a second terminal electrically coupled to the second output 2 ; a seventh diode D 7 having an anode electrically coupled to the input of the ground fault simulation unit, and a cathode electrically coupled to both the first terminal of the first resistor R 1 and the first terminal of the second resistor R 2 ; a first transistor Q 1 having a first collector electrically coupled to the second terminal of the first resistor R 1 , a first emitter electrically coupled to the second input of the leakage current protection device, and a base; and a sixth zener diode D 6 having an anode electrically coupled to the base of the first transistor Q 1 , and a cathode electrically coupled to both the second terminal of the second resistor R 2 and the first terminal of the third resistor R 3 .

In yet another embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and a second terminal; a seventh diode D 7 having an anode electrically coupled to the input, and a cathode electrically coupled to the first terminal of the resistor R 1 ; and a transformer T 1 having a primary winding having a first primary terminal P 1 and a second primary terminal P 2 , and a secondary winding having a first secondary terminal S 1 and a second secondary terminal S 2 , wherein the first primary terminal P 1 is electrically coupled to the second terminal of the first resistor R 1 , the second primary terminal P 2 is electrically coupled to the second input of the leakage current protection device, the first secondary terminal S 1 is electrically coupled to the second secondary terminal S 2 through the first inductive coil N 1 and the second inductive coil N 2 .

In an alternative embodiment, the ground fault simulation unit has: a seventh diode D 7 having a cathode and an anode electrically coupled to the input; and a first resistor R 1 having a first terminal electrically coupled to the cathode of the seventh diode D 7 , and a second terminal electrically coupled to the output.

In yet an alternative embodiment, the ground fault simulation unit has: a first resistor R 1 having a first terminal and second terminal; a seventh diode D 7 having an anode electrically coupled to the input, and a cathode electrically coupled to the first terminal of the first resistor R 1 ; and a sixth zener diode D 6 having a cathode electrically coupled to the second terminal of the first resistor R 1 , and an anode electrically coupled to the output.

These and other aspects of the present invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.

The accompanying drawings illustrate one or more embodiments of the invention and, together with the written description, serve to explain the principles of the invention.

Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein:

FIG. 1 shows a block diagram of an apparatus for intelligently testing the life of a leakage current protection device according to one embodiment of the present invention;

FIG. 2 shows a circuit diagram of an apparatus for intelligently testing the life of a leakage current protection device according to one embodiment of the present invention;

FIG. 3 shows (A) an AC power signal waveform; (B) a waveform measured at a first end of the trip coil J, point V 3 shown in FIG. 2 , and (C) the waveform of a simulated ground fault current according to embodiments of the present invention; and

FIG. 4 shows four different embodiments (A)-(D) of a ground fault simulation unit according to embodiments of the present invention.

The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. Moreover, titles or subtitles may be used in the specification for the convenience of a reader, which has no influence on the scope of the invention. Additionally, some terms used in this specification are more specifically defined below.

The terms used in this specification generally have their ordinary meanings in the art, within the context of the invention, and in the specific context where each term is used.

Certain terms that are used to describe the invention are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner in describing the apparatus and methods of the invention and how to make and use them. For convenience, certain terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no influence on the scope and meaning of a term; the scope and meaning of a term is the same, in the same context, whether or not it is highlighted. Whether or not a term is capitalized is not considered definitive or limiting of the meaning of a term. As used in the description herein and throughout the claims that follow, a capitalized term shall have the same meaning as an uncapitalized term, unless the context of the usage specifically indicates that a more restrictive meaning for the capitalized term is intended. It will be appreciated that the same thing can be said in more than one way. Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the invention or of any exemplified term. Likewise, the invention is not limited to various embodiments given in this specification. Furthermore, subtitles may be used to help a reader of the specification to read through the specification, which the usage of subtitles, however, has no influence on the scope of the invention.

As used herein, “around”, “about” or “approximately” shall generally mean within 20 percent, preferably within 10 percent, and more preferably within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term “around”, “about” or “approximately” can be inferred if not expressly stated.

As used herein, the terms “unit” and “circuit” are interchangeable, and refer to a configuration of electrically or electromagnetically electrically coupled components or devices.

The term “switch” or “switching device”, refers to a device for changing the course (or flow) of a circuit, i.e., a device for making or breaking an electric circuit, or for selecting between multiple circuits. As used herein, a switch or switching device has two states: a conductive state and a non-conductive state. When the switching device is in the conductive state, a current is allowed to pass through. When the switching device is in the non-conductive state, no current is allowed to pass through.

As used herein, short names, acronyms and/or abbreviations “AC” refers to alternate current; “DC” refers to direct current; “AFCI” refers to arc fault circuit interrupter; “GFCI” refers to ground fault circuit interrupter; “LED” refers to light emitting diode; “MCU” refers to microcontroller unit; and “SCR” refers to silicon controlled rectifier.

The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings in FIGS. 1-4 . In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to apparatus for intelligently testing the life of a leakage current protection device.

Referring to FIGS. 1-4 , and particularly to FIGS. 1 and 2 first, an apparatus 300 for intelligently testing the life of a leakage current protection device, according to embodiments of the present invention, has a leakage current protection device 100 , a ground fault simulation unit 250 and an intelligent life testing and alarm circuit 200 .

The leakage current protection device 100 has a first input 151 , a second input 153 , a first output 172 , a second output 174 , a third output 176 . The leakage current protection device 100 further has a power supply circuit 102 having an input 102 a electrically coupled to the first input 151 , and an output 102 b electrically coupled to the second output 174 . Moreover, the leakage current protection device 100 has a trip coil circuit 103 having an input 103 a , an output 103 b electrically coupled to the third output 176 . Additionally, the leakage current protection device 100 has a leakage current detection circuit 107 having an output 107 b electrically coupled to the input 103 a of the trip coil circuit 103 , and a power supply input 107 p electrically coupled to the output 102 b of the power supply circuit 102 and the second output 174 . The leakage current protection device 100 also has a trip switch SW 101 , a manual testing circuit 104 and a metal oxide varistors (MOV) MOV 1 . Furthermore, the leakage current protection device 100 has a first inductive coil N 1 and a second inductive coil N 2 coupled with the line phase and neutral wires of an AC power for detecting leakage current.

The trip switch SW 101 has two LINE terminals 151 a and 153 a that are electrically coupled to the first input 151 and the second input 153 , through the first inductive coil N 1 and the second inductive coil N 2 , respectively, and two LOAD terminals 151 b and 153 b electrically connected to one or more electric appliances. The first input 151 and the second input 153 are electrically connected to an incoming AC power. When the trip switch SW 101 is in a conductive state, the AC power is connected from the LINE terminals 151 a and 153 a to the LOAD terminals 151 b and 153 b . When the SW 101 is in a non-conductive state, the AC power to the LOAD terminals 151 b and 153 b is disconnected from the LINE terminals 151 a and 153 a . The LOAD terminals 151 b and 153 b may be also connected to an outlet receptacle.

The two inductive coils N 1 and N 2 are adapted for detecting leakage current. When a current passing through a first input 151 to the LOAD terminal 151 b of the trip switch SW 101 is substantially different from a current passing through the second input 153 for the LOAD terminal 153 b , the inductive coils N 1 and N 2 detect the difference and a leakage current is consequently sent to the leakage current detection circuit 107 .

When the leakage current detection circuit 107 receives the leakage current from the inductive coils N 1 and N 2 , and it compares the leakage current with a predetermined threshold. If the leakage current is greater than the predetermined threshold, a ground fault exists, then the leakage current detection circuit 107 sends a signal to the trip coil circuit 103 to disconnect the AC power from the LINE terminals 151 a and 153 a to the LOAD terminals 151 b and 153 b . The leakage current detection circuit 107 is a part of leakage current protection device 100 and known to those skilled in the art.

The half-wave power supply circuit 102 has a fifth diode D 5 having an anode and a cathode and a seventh current limiting resistor R 7 having a first and second terminals and an eighth current limiting resistor R 8 having a first and second terminals. The anode of the fifth diode D 5 is electrically connected to the second input 153 that is connected the one of the line phase and neutral wires of the AC power, and the cathode of the fifth diode D 5 is electrically connected to both the first terminals of the resistor R 7 and the resistor R 8 . The second terminal of the resistor R 7 is electrically connected to the input 107 a of the leakage current detection circuit 107 . For such a configuration, the current at the cathode of the fifth diode D 5 is direct current. The current limiting resistors are used to convert the current into a voltage and reduce it at the output. The power supply 102 is connected through the second terminal of the seventh resistor R 7 to the leakage current detection circuit 107 . The power supply 102 is also connected through the second terminal of the eighth resistor R 8 to a fault alarm circuit 202 .

The trip coil circuit 103 includes a switching device VD 1 having a gate, an anode and a cathode, a first capacitor C 1 having a first and second terminals, a twelfth resistor R 12 , and a trip coil J electrically connected between the trip mechanism state generator 201 and the anode of the switching device VD 1 . The cathode of the switching device VD 1 is electrically connected to the fault alarm circuit 202 . The twelfth resistor R 12 is electrically connected between the gate of the switching device VD 1 and the output 107 b of the leakage current detection circuit 107 . The first capacitor C 1 has its first terminal connected to the output 107 b of the leakage current detection circuit 107 and its second terminal connected to the fault alarm circuit 202 , as shown in FIG. 2 . An input signal to the gate of the switching device VD 1 from the output 107 b of the leakage current detection circuit 107 through the twelfth resistor R 12 makes the switching device VD 1 either in a conductive or a non-conductive state. When the switching device VD 1 is in the conductive state, the trip coil J is connected to the power supply and the trip coil sets the trip switch SW 101 into a non-conductive state (a trip state).

The manual testing circuit 104 has a resistor R 0 and a push-on release-off switch TEST that are connected in series. The manual testing circuit 104 is electrically connected between the MOV 1 and the LOAD terminal 151 b of the trip switch SW 101 and adapted for manually testing the leakage current protection device 100 .

The trip switch SW 101 maintains its state until a current passes through the trip coil J. The trip switch SW 101 responds to the action of the trip coil J. When the leakage current detection circuit 107 detects the leakage current, a signal from the leakage current detection circuit is sent to the gate of the switching device VD 1 , which sets the switching device VD 1 to its conductive state. The power supply 102 energizes the trip coil J to set the trip switch SW 101 in its non-conductive state so that the AC power is disconnected from the LINE terminals 151 a and 153 a to the LOAD terminals 151 b and 153 b , i.e. in a trip state. If the leakage current protection device 100 does not have an automatic reset circuit, the leakage current protection device in a trip state can be manually reset by pressing a reset button.

As shown in FIG. 1 , the apparatus 300 includes a trip mechanism state generator 201 having a first input 201 a 1 electrically coupled to the third output 176 of the leakage current protection device 100 , a second input 201 a 2 electrically coupled to the first input 151 of the leakage current protection device 100 , a third input 201 a 3 electrically coupled to the second input 153 of the leakage current protection device 100 , a first output 201 b 1 and a second output 201 b 2 . The trip mechanism state generator 201 is adapted for generating a trip mechanism state at the first output 201 b 1 and the second output 201 b 2 , where the trip mechanism state has a first state and a second state. When the trip mechanism state is in the first state, there is no fault exist in the leakage current protection device 100 . When the trip mechanism state is in the second state, there is at least one fault exists in the leakage current protection device 100 .

As shown in FIG. 2 , the trip mechanism state generator 201 has a first diode D 1 having a cathode and an anode electrically coupled to the second input 201 a 2 of the trip mechanism state generator 201 ; a second diode D 2 having a cathode electrically coupled to both the cathode of the first diode D 1 and the first input 201 a 1 of the trip mechanism state generator 201 , and an anode electrically coupled to the third input 201 a 3 of the trip mechanism state generator 201 ; a third diode D 3 having an anode and a cathode electrically coupled to both the second input 153 of the leakage current protection device 100 and the anode of the second diode D 2 ; a fourth diode D 4 having a cathode electrically coupled to both the anode of the first diode D 1 and the first input 151 of the leakage current protection device 100 , and an anode electrically coupled to a first output 201 b 1 of the trip mechanism state generator 201 ; a fifth resistor R 5 having a first terminal electrically coupled to the first output 201 b 1 of the trip mechanism state generator 201 , and a second terminal electrically coupled to the second output 201 b 2 ; and a sixth resistor R 6 having a first terminal electrically coupled to the second terminal of the fifth resistor R 5 and the second output 201 b 2 of the trip mechanism state generator 201 , and a second terminal electrically coupled to the anode of the third diode D 3 .

The trip mechanism state generator 201 generates two distinct states: one indicating that the trip mechanism of the leakage current protection device 100 is working properly, and the other indicating that the trip mechanism of the leakage current protection device 100 is out of order. The trip mechanism state generator 201 is an asymmetric bridge rectifying circuit. The bridge rectifying circuit provides a first current path and a second current path. In one embodiment, the first path starts from a first wire of an AC power (for example, through the first input 151 of the leakage current protection device 100 ), going through the first diode D 1 , the trip coil J, the switching device VD 1 of the trip coil circuit 103 , the fifth resistor R 5 , the sixth resistor R 6 , the third diode D 3 and returning to the second wire of the AC power (for example, through the second input 153 of the leakage current protection device 100 ). The second path starts from the second wire of the AC power, going through the second diode D 2 , the trip coil J, the switching device VD 1 of the trip coil circuit 103 , the fourth diode D 4 and returning to the first wire of the AC power. The first wire of the AC power can be one of a hot wire and a neutral wire, whole the second wire of the AC power is chosen to be the other of a hot wire and a neutral wire.

The apparatus 300 also includes a fault alarm generator 202 having a first input 202 a 1 electrically coupled to the first output 201 b 1 of the trip mechanism state generator 201 , a second input 202 a 2 electrically coupled to the second output 201 b 2 of the trip mechanism state generator 201 , and a power supply input 202 p electrically coupled to the second output 172 of the leakage current protection device 100 , as shown in FIG. 1 .

As shown in FIG. 2 , the fault alarm circuit 202 comprises a light emitting diode (LED) D 8 , a second transistor Q 2 , a third transistor Q 3 , a second capacitor C 2 , a third capacitor C 3 , a ninth resistor R 9 , a tenth resistor R 10 and a eleventh resistor R 11 . The fault alarm circuit 202 is a multi-vibrator. The input to the fault alarm circuit 202 is the voltage between the base of the second transistor Q 2 and the emitters of the second and the third transistors Q 2 and Q 3 . These two terminals are connected to both ends of the fifth resistor R 5 of the trip mechanism state generator 201 . When the voltage is greater than a predetermined level, a vibration is started in the fault alarm circuit 202 and the LED D 8 starts to flash, indicating at least one fault exists in the trip mechanism of the leakage current protection device. When the voltage is less than the predetermined level, the multi-vibrator will not vibrate in the fault alarm circuit 202 and the LED D 8 remains dark, indicating no fault exists in the trip mechanism of the leakage current protection device. In one embodiment, the predetermined level of the voltage can be set to zero. Therefore, when the fault alarm circuit 202 receives a negative DC voltage, the multi-vibrator generates no vibration indicating that there is no fault in the leakage current protection device 100 . When the fault alarm circuit 202 receives a positive DC voltage, the multi-vibrator generates vibrations and a visible alarm through the LED D 8 indicating that there is at least one fault in the leakage current protection device 100 . The fault alarm circuit 202 may include an audio alarm circuit for generating an audible alarm.

In one embodiment, the DC voltage is detected at the first terminal and the second terminal of the resistor R 5 of the trip mechanism state generator 201 .

Furthermore, the apparatus 300 further includes a ground fault simulation unit 250 having an input 250 a electrically coupled to the first input 151 of the leakage current protection device 100 , and an output 250 b electrically coupled to the first output 172 of the leakage current protection device 100 , as shown in FIG. 1 .

As shown in FIG. 2 , the ground fault simulation unit 250 has a first resistor R 1 having a first terminal and a second terminal; a second resistor R 2 having a first terminal and a second terminal; a third resistor R 3 having a first terminal and a second terminal; a seventh diode D 7 having a cathode and an anode, wherein the anode of the seventh diode D 7 is connected to the input 250 a that is electrically coupled to a first wire of an AC power through the first input 151 of the leakage current protection device 100 , and the cathode of the seventh diode D 7 is connected to both the first terminal of the resistor R 1 and the first terminal of the second resistor R 2 ; a first transistor Q 1 having a first collector electrically coupled to the second terminal of the first resistor R 1 , a first emitter electrically coupled to both the second terminal of the third resistor R 3 and the output terminal 250 b , and a first base; and a sixth zener diode D 6 having an anode electrically coupled to the base of the first transistor Q 1 , and a cathode electrically coupled to both the second terminal of the second resistor R 2 and the first terminal of the third resistor R 3 .

This output terminal 250 b of the ground fault simulation unit 250 is connected to a second wire of the AC power after the second wire (the first input terminal 153 of the leakage current protection device 100 , for example) passes the first and the second inductive coils N 1 and N 2 . During a positive half-wave of the AC power, the first transistor Q 1 is in a non-conductive state at first. As the input voltage increases, the first transistor Q 1 remains in its non-conductive state until the input voltage is greater than the voltage difference between the collector terminal and the emitter terminal of the first transistor Q 1 . At this point the first transistor Q 1 becomes conductive. After the input voltage reaches its peak and the first transistor Q 1 remains conductive until the input voltage is less than the voltage difference between the collector terminal and the emitter terminal of the first transistor Q 1 . At this point the first transistor Q 1 becomes non-conductive. The first transistor Q 1 remains non-conductive until the input voltage is greater than the voltage difference between the collector terminal and the emitter terminal of the first transistor Q 1 during the next positive half-wave of the AC power. A square wave signal is formed at the output of the ground fault simulation unit 250 as a simulated ground fault signal.

Referring now to FIG. 3 , three signal waveforms are presented according to one embodiment of the present invention. FIG. 3A is a signal wave form of the AC power input shown in full cycle measured at the input of the ground fault simulation unit 250 marked as V 1 . FIG. 3B shows the signal wave form measured at an output of an asymmetric bridge rectifier circuit marked as V 3 . FIG. 3C is the square wave signal measured at the output of the ground fault simulation unit 250 . The shape of the square wave can be adjusted by varying the parameter of the ground fault simulation unit 250 .

FIG. 4 also shows alternative embodiments of the ground fault simulation unit 250 . As shown in FIG. 3A , the ground fault simulation unit 250 has a first resistor R 1 having a first terminal and a second terminal; a second resistor R 2 having a first terminal and a second terminal; a third resistor R 3 having a first terminal and a second terminal electrically coupled to the second output 250 b 2 ; a seventh diode D 7 having an anode electrically coupled to the input 250 a of the ground fault simulation unit 250 , and a cathode electrically coupled to both the first terminal of the first resistor R 1 and the first terminal of the second resistor R 2 ; a first transistor Q 1 having a first collector electrically coupled to the second terminal of the first resistor R 1 , a first emitter electrically coupled to the second input 153 of the leakage current protection device 100 , and a base; and a sixth zener diode D 6 having an anode electrically coupled to the base of the first transistor Q 1 , and a cathode electrically coupled to both the second terminal of the second resistor R 2 and the first terminal of the third resistor R 3 . The input 205 a of the ground fault simulation unit 250 is electrically connected to a first wire of the AC power, while the output 250 b of the ground fault simulation unit 250 is electrically connected to a second wire of the AC passed the first inductive coil N 1 and the second inductive coil N 2 .

As shown in FIG. 4B , the ground fault simulation unit 250 has: a first resistor R 1 having a first terminal and a second terminal; a seventh diode D 7 having an anode electrically coupled to the input 250 a , and a cathode electrically coupled to the first terminal of the resistor R 1 ; and a transformer T 1 having a primary winding having a first primary terminal P 1 and a second primary terminal P 2 , and a secondary winding having a first secondary terminal S 1 and a second secondary terminal S 2 , wherein the first primary terminal P 1 is electrically coupled to the second terminal of the first resistor R 1 , the second primary terminal P 2 is electrically coupled to the second input 153 of the leakage current protection device 100 , the first secondary terminal S 1 is electrically coupled to the second secondary terminal S 2 through the first inductive coil N 1 and the second inductive coil N 2 .

As shown in FIG. 4C , the ground fault simulation unit 250 has a seventh diode D 7 having a cathode and an anode electrically coupled to the input 250 a ; and a first resistor R 1 having a first terminal electrically coupled to the cathode of the seventh diode D 7 , and a second terminal electrically coupled to the output 250 b . The input 205 a of the ground fault simulation unit 250 is electrically connected to a first wire of the AC power, while the output 250 b of the ground fault simulation unit 250 is electrically connected to a second wire of the AC passed the first inductive coil N 1 and the second inductive coil N 2 .

As shown in FIG. 4D , the ground fault simulation unit 250 has a first resistor R 1 having a first terminal and second terminal; a seventh diode D 7 having an anode electrically coupled to the input 250 a , and a cathode electrically coupled to the first terminal of the first resistor R 1 ; and a sixth zener diode D 6 having a cathode electrically coupled to the second terminal of the first resistor R 1 , and an anode electrically coupled to the output 250 b . The input 205 a of the ground fault simulation unit 250 is electrically connected to a first wire of the AC power, while the output 250 b of the ground fault simulation unit 250 is electrically connected to a second wire of the AC passed the first inductive coil N 1 and the second inductive coil N 2 .

In operation, the ground fault simulation unit 250 generates a simulated ground fault signal during every positive half-wave of the AC power, the simulated ground fault signal is detected by the leakage current detection circuit 107 , the leakage current detection circuit 107 responsively generates a signal to turn the switching device VD 1 into its conductive state so as to allow a current to pass therethrough, the passed current is converted into a DC voltage in accordance with a trip mechanism state generated by the trip mechanism state generator 201 , the fault alarm circuit 202 receives and analyzes the DC voltage and indicates whether a fault exists in the leakage current protection device 100 .

Specifically, referring to FIG. 2 , the ground fault simulation unit 250 generates a simulated ground fault during every positive half-wave of an AC power. The current after the seventh diode D 7 is connected to a voltage divider having the second resistor R 2 and the third resistor R 3 to the second wire of the AC power. The ratio of the voltage divider is determined by the values of these two resistors R 2 and R 3 . During the positive half-wave of the AC power, the voltage across R 2 increases until the voltage exceeds the relative consistent voltage maintained at the sixth zener diode D 6 and the sixth zener diode D 6 becomes conductive. Then the first transistor Q 1 becomes conductive as a result of the sixth zener diode D 6 becoming conductive. After the AC power reaches its peak, the input voltage of the AC power starts to decrease. The voltage at the cathode of the seventh diode D 7 reaches a point where the sixth zener diode D 6 becomes non-conductive. The first transistor Q 1 becomes non-conductive as a result, thus forming the square wave simulated ground fault signal as shown in FIG. 2C . This process repeats every positive half-wave. An approximated square wave or other non-square wave signals can also be used for simulating ground faults.

The simulated ground fault signal is detected by two inductive coils N 1 and N 2 and sent to a leakage current detection circuit 107 for processing. The output of the leakage current detection circuit 107 is fed to a trip coil circuit 103 . The trip coil circuit 103 comprises a twelfth resistor R 12 , a silicon controlled rectifier VD 1 , a coil J for the trip mechanism. The simulated ground fault signal enables the leakage current detection circuit 107 to output a signal to turn the SCR VD 1 into conductive state. During this time, a trip mechanism state generator 201 generates a state related to the status of the trip mechanism. The trip mechanism state generator 201 comprises a first diode D 1 , a second diode D 2 , a third diode D 3 , a fourth diode D 4 , a fifth resistor R 5 and a sixth resistor R 6 . These components form an asymmetric rectifying bridge providing current through the trip coil circuit 103 .

During positive half-wave of the AC power, a first path of current is formed from a first wire of the AC power to the second wire of the AC power through the first diode D 1 , the trip coil J, the VD 1 , the fifth resistor R 5 , the sixth resistor R 6 and the third diode D 3 . The values of the resistors R 5 and R 6 are selected so that the current passing through the first path of current is small enough not to trip the trip mechanism. During negative half-wave of the AC power, a second path of current is formed from the second wire of the AC power to the first wire of the AC power through the second diode D 2 , the trip coil J, the VD 1 , and the fourth diode D 4 . When the inductive coils N 1 and N 2 , an IC inside the leakage current detection circuit, the SCR VD 1 are working properly, the current through the first path generates a negative voltage across the fifth resistor R 5 , i.e. the voltage at the point marked as O 2 is lower than the voltage at the point marked as O 1 . This negative voltage indicates the proper working order of the leakage current protection device. Otherwise, if the leakage current detection circuit 107 fails to detect the simulated ground fault, if the trip coil J is broken so the current could not pass through the first path, or if the VD 1 fails to respond to the signal from the leakage current detection circuit 107 , a current can not pass through the first path and the negative voltage can not be established across the fifth resistor R 5 . Therefore, the negative voltage across the fifth resistor R 5 , marked as O 1 and O 2 , reflects the status of the leakage current protection device.

The both terminals of the fifth resistor R 5 , marked as O 1 and O 2 , are connected to two input terminals of a fault alarm circuit 202 . The fault alarm circuit 202 comprises a second transistor Q 2 , a third transistor Q 3 , a light emitting diode (LED) D 8 , a second capacitor C 2 , a third capacitor C 3 , a ninth resistor R 9 , a tenth resistor R 10 and a eleventh resistor R 11 . The fault alarm circuit 202 is a multi-vibrator. When the voltage between the two input terminals (the voltage across the fifth resistor R 5 ) is negative, the second transistor Q 2 is in non-conductive state and the LED D 8 is not lit. If the voltage between the two input terminals is not negative, the multi-vibrator vibrates and the LED D 8 flashes. The frequency of the LED D 8 flashing depends on the parameters of the components used in the multi-vibrator. The flashing frequency can be chosen from any numbers of flashes per second as long as the flashing can be identified by human eyes. In one embodiment, the flashing rate is one flash per second. The flashing rate can be lower than one flash per second, and also can be higher that one flash per second. Optionally, additional audio alarm circuit can be added to the fault alarm circuit 202 .

Another aspect of the present invention provides a method of intelligently testing the life of a leakage current protection device having a leakage current detection circuit and a trip mechanism. In one embodiment, the method comprises the steps of:

detecting fault in leakage current protection device with a fault detector; and alerting user of the leakage current protection device with a life testing detection unit having an fault alarm circuit when at least one fault is detected in the leakage current protection device.

The step of detecting fault in leakage current protection device with a fault detector comprising the step of detecting fault in a leakage current detection circuit of the leakage current protection device with the fault detector having (i) a trip mechanism state generator, (ii) a ground fault simulation unit, and (iii) a fault alarm circuit having a multivibrator.

The step of alerting user of the leakage current protection device when at least one fault is detected in the leakage current protection device comprises the step of alerting user of the leakage current protection device by producing a visible visual alarm.

The step of detecting fault in leakage current protection device with the fault detector comprising the steps of:

producing a simulated ground fault by the ground fault simulation unit during positive half-wave of an AC power; generating a trip mechanism state by the trip mechanism state generator; detecting the trip mechanism state; and determining whether at least one fault exists in the trip mechanism of the leakage current protection device.

If no fault exists in the leakage current detection circuit of the leakage current detection device, the trip mechanism state disables the vibration of the multivibrator of the fault alarm circuit. If at least one fault exists in the leakage current detection circuit of the leakage current protection device, the trip mechanism state enables the vibration of the multivibrator of the fault alarm circuit.

In another embodiment, the method for intelligently testing the life of a leakage current protection device includes the steps of providing a life testing device as disclosed above; generating a simulated ground fault signal during every positive half-wave of the AC power by the ground fault simulation unit; detecting the simulated ground fault signal at the leakage current detection circuit; generating a signal to turn the switching device VD 1 into its conductive state so as to allow a current to pass therethrough; generating a DC voltage in responsive to a trip mechanism state at the trip mechanism state generator, wherein the trip mechanism state is in a first state that there is no fault exist in the leakage current protection device, or in a second state that there is at least one fault exists in the leakage current protection device; receiving the DC voltage at the fault alarm circuit; and indicating whether at least one fault exists in the leakage current protection device. In one embodiment, the indicating step includes the step of producing a visible alarm and/or an audible alarm.

The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.