Tester for Frequency-Related Ground Fault Interruption Wiring Device

Abstract

The present invention discloses a tester for a frequency-related ground fault interruption wiring device, including a tester circuit. The tester circuit includes: a switch disposed between a first terminal and a second terminal, wherein when a voltage is applied between the first terminal and the second terminal, a leakage current flows through a leakage path between the first terminal and the second terminal, and the magnitude of the leakage current is at least partially determined by the conductivity of the switch; and a waveform generator configured to generate a periodic output signal having a frequency; wherein the switch is driven to modulate the magnitude of the leakage current such that the frequency of the leakage current is substantially equal to the frequency of the waveform generator.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit and priority of U.S. Provisional Patent Application No. 62 / 982,394, filed on February 27, 2020, the entire content of which is incorporated herein by reference. Technical Field

[0003] This application generally relates to a test device for a ground - fault interrupt wiring device, and more particularly, to a test device for a frequency - related ground - fault interrupt wiring device. Background Art

[0004] Modern electrical appliances employ switched - mode power supplies that often leak high - frequency currents to the ground. A ground - fault circuit interrupter (GFCI) wiring device is designed to protect users from electric shock caused by current leakage. It can interpret such high - frequency current leakage as a dangerous current leakage and trip, preventing power flow to the wiring device outlet. However, high - frequency currents, as demonstrated by the Dalziel curve, are not as dangerous as low - frequency current leakage. Thus, the tripping of a GFCI wiring device in response to high - frequency current leakage from a switched - mode power supply is not always dangerous. This means that such tripping can generally be classified as a nuisance trip - i.e., an unnecessary trip that only annoys the user, who now has to reset the GFCI wiring device to continue using the appliance that caused the trip.

[0005] Typically, to create a fault at the 60 Hz fundamental frequency, a passive impedance (such as a resistor / inductor / capacitor network) is placed to form a path from the load hot to the neutral line. In such a case, the fault current takes the form of the fundamental frequency and does not contain any other frequency content. Thus, there is a need in the art for an active circuit that is designed to allow leakage currents other than the 60 Hz fundamental frequency. Summary of the Invention

[0006] The examples described in this disclosure can be combined in any technically possible way.

[0007] According to one aspect, a tester for a frequency-related ground fault interruption wiring device is disclosed, comprising: a tester circuit including: a switch disposed between a first terminal and a second terminal, wherein when a voltage is applied between the first terminal and the second terminal, a leakage current flows through a leakage path between the first terminal and the second terminal, and the magnitude of the leakage current is at least partially determined by the conductivity of the switch; a waveform generator configured to generate a waveform generator output signal; and a comparator configured to generate a comparator output signal based on a comparison between the waveform generator output signal and a current sensing signal representing the leakage current, wherein the conductivity of the switch is adjusted according to the comparator output signal such that the leakage current follows the waveform generator output signal.

[0008] In an example, the waveform generator output signal is a periodic waveform having a frequency, wherein the frequency of the waveform generator output signal is greater than the frequency of the voltage applied between the first terminal and the second terminal.

[0009] In an example, the voltage applied between the first terminal and the second terminal is a power supply voltage.

[0010] In an example, the tester further includes a second switch disposed between the first terminal and the second terminal, wherein during a negative half-cycle of the voltage applied between the first terminal and the second terminal, a second leakage current flows through a second leakage path, and the magnitude of the second leakage current is at least partially determined by the conductivity of the second switch, and wherein during a positive half-cycle of the voltage applied between the first terminal and the second terminal, the leakage current flows through the leakage path.

[0011] In an example, the tester further includes a second comparator configured to generate a second comparator output signal based on a comparison between an inverted periodic output signal, which is an inversion of the periodic output signal, and a second current signal representing the second leakage current, wherein the conductivity of the second switch is adjusted according to the second comparator output signal such that the frequency of the second leakage current is substantially equal to the frequency of the waveform generator.

[0012] In an example, the waveform generator includes a voltage-controlled oscillator.

[0013] In an example, the waveform generator output signal is a periodic waveform having a frequency, wherein the waveform generator is configured to change the frequency of the periodic output signal.

[0014] In an example, the waveform generator is configured to change the magnitude of the waveform generator output signal.

[0015] In an example, the output signal of the waveform generator is a non-sinusoidal output signal.

[0016] In an example, the output of the waveform generator is non-periodic.

[0017] In an example, the voltage applied between the first terminal and the second terminal is a full-wave rectified supply voltage.

[0018] In an example, the first terminal is in electrical communication with the load hot terminal of the frequency-dependent ground fault interrupt wiring device, and the second terminal is in electrical communication with the ground terminal of the frequency-dependent ground fault interrupt wiring device.

[0019] In an example, the tester circuit is disposed within a housing, wherein the housing includes a plurality of blades sized and arranged to engage a receptacle of the frequency-dependent ground fault interrupt wiring device, wherein the first terminal is in electrical communication with the load hot terminal through one of the plurality of blades that engages the load hot receptacle of the frequency-dependent ground fault interrupt wiring device, and the second terminal is in electrical communication with the ground terminal through one of the plurality of blades that engages the ground receptacle of the frequency-dependent ground fault interrupt wiring device.

[0020] In an example, the first terminal is in electrical communication with the load hot terminal of the frequency-dependent ground fault interrupt wiring device, wherein the second terminal is in electrical communication with the line neutral terminal of the frequency-dependent ground fault interrupt wiring device.

[0021] In an example, the first terminal is in electrical communication with the line hot terminal of the frequency-dependent ground fault interrupt wiring device, wherein the second terminal is in electrical communication with the load neutral terminal of the frequency-dependent ground fault interrupt wiring device.

[0022] According to another aspect, a tester for a frequency-dependent ground fault interrupt wiring device is disclosed, comprising: a tester circuit including: a switch disposed between a first terminal and a second terminal, wherein when a voltage is applied between the first terminal and the second terminal, a leakage current flows through a leakage path between the first terminal and the second terminal, and the magnitude of the leakage current is at least partially determined by the conductivity of the switch; and a waveform generator configured to generate a waveform generator output signal, wherein the switch is driven to modulate the magnitude of the leakage current such that the leakage current follows the waveform generator output signal.

[0023] In an example, the waveform generator output signal is a periodic waveform having a frequency, wherein the frequency of the waveform generator output signal is greater than the frequency of the voltage applied between the first terminal and the second terminal.

[0024] In an example, the voltage applied between the first terminal and the second terminal is a supply voltage.

[0025] In an example, the tester further includes a second switch disposed between the first terminal and the second terminal, wherein during a negative half-cycle of the voltage applied between the first terminal and the second terminal, a second leakage current flows through a second leakage path, and a magnitude of the second leakage current is at least partially determined by a conductivity of the second switch, and wherein during a positive half-cycle of the voltage applied between the first terminal and the second terminal, the leakage current flows through the leakage path.

[0026] In an example, the waveform generator includes a voltage-controlled oscillator.

[0027] In an example, the output signal of the waveform generator is a periodic waveform having a frequency, and wherein the waveform generator is configured to change the frequency of the periodic output signal.

[0028] In an example, the waveform generator is configured to change a magnitude of the periodic output signal.

[0029] In an example, the output signal of the waveform generator is a non-sinusoidal output signal.

[0030] In an example, the output of the waveform generator is non-periodic.

[0031] In an example, the voltage applied between the first terminal and the second terminal is a full-wave rectified supply voltage.

[0032] In an example, the first terminal is in electrical communication with a load hot terminal of the frequency-dependent ground fault interruption wiring device, and the second terminal is in electrical communication with a ground terminal of the frequency-dependent ground fault interruption wiring device.

[0033] In an example, the tester circuit is disposed within a housing, and wherein the tester includes a plurality of blades sized and arranged to engage a receptacle of the frequency-dependent ground fault interruption wiring device, and wherein the first terminal is in electrical communication with the load hot terminal through one of the plurality of blades that engages a load hot receptacle of the frequency-dependent ground fault interruption node device, and wherein the second terminal is in electrical communication with the ground terminal through one of the plurality of blades that engages a ground receptacle of the frequency-dependent ground fault interruption wiring device.

[0034] In an example, the first terminal is in electrical communication with a load hot terminal of the frequency-dependent ground fault interruption wiring device, and the second terminal is in electrical communication with a line neutral terminal of the frequency-dependent ground fault interruption wiring device.

[0035] In an example, the first terminal is in electrical communication with the line hot terminal of the frequency - related ground - fault interrupt wiring device, and the second terminal is in electrical communication with the load neutral terminal of the frequency - related ground - fault interrupt wiring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be more fully understood and appreciated by reading the following detailed description in conjunction with the accompanying drawings: The drawings only illustrate typical embodiments of the disclosed subject matter and should not be considered as limiting its scope, since the disclosed subject matter may admit other equivalent embodiments. Now briefly refer to the drawings, wherein:

[0037] Figure 1 Illustrates a tester for testing a frequency - related ground - fault interrupt wiring device according to an example.

[0038] Figure 2 Illustrates a schematic diagram of a tester circuit for testing a frequency - related ground - fault interrupt wiring device according to an example.

[0039] Figure 3 Illustrates a timing diagram of a tester circuit for a frequency - related ground - fault interrupt wiring device according to an example. DETAILED DESCRIPTION

[0040] The various examples described herein relate to a test circuit and apparatus that modulates leakage current to test the trip threshold of a GFCI wiring device at frequencies other than the fundamental frequency of the supply voltage. Alternatively or additionally, the test circuit and apparatus are capable of modulating the leakage current using any non - sinusoidal waveform including non - periodic waveforms. Such non - sinusoidal waveforms can be used to test the response of the wiring device to, for example, a harmful load or an arc fault.

[0041] Figure 1 Depicts a ground - fault circuit interrupter outlet tester 100 for testing a frequency - related ground - fault interrupt (GFCI) wiring device. As shown, the tester 100 includes a housing 102 that houses the tester circuit (in Figure 2(An example of the tester circuit 200 is described in detail). A set of blades 104 extends from the housing 102 and is sized and arranged to be inserted into the receptacle of a frequency - related GFCI wiring device. At a high level, when the tester 100 is inserted into the GFCI wiring device, current leaks thermally from the load to ground. In other words, the current flowing through the thermal conductor to the load hot terminal returns through ground rather than through the neutral conductor. The GFCI wiring device monitors the current difference between the hot conductor and the neutral conductor and detects that the current in the hot conductor is different from the current in the neutral conductor. If the difference is greater than the trip threshold for a predetermined time (e.g., 5 ms) and the GFCI wiring device is operational, the GFCI wiring will trip. It should be understood that the exact form of the housing 102 and the blades 104 of the tester 100 can vary as long as the tester 100 houses a circuit that engages with the GFCI wiring device and tests the trip threshold of the GFCI wiring device by modulating the leakage current at a frequency greater than the fundamental frequency of the supply voltage.

[0042] For the purposes of the present invention, leakage current is defined as any current that flows through the GFCI hot conductor to the load and does not return through the GFCI neutral conductor, or any current that flows through the GFCI neutral conductor to the load and does not return through the GFCI hot conductor, such that the current difference between the hot conductor and the neutral conductor is detected by the toroidal coil of the GFCI wiring device. Here, the load is not necessarily a connected device but should be understood as the ultimate destination of the current.

[0043] Figure 2 A circuit schematic of an example tester circuit 200 to be included in the tester 100 is depicted. The example tester circuit 200 modulates the leakage current according to a waveform generator V1, which in some instances is capable of generating a frequency greater than the fundamental frequency of the supply voltage. As shown, in this example, the tester circuit 200 includes a waveform generator V1 and at least one switch Q1, Q2 that modulates the current flowing through at least one leakage path according to the output of the waveform generator V1. More specifically, in this example, the main active leakage current paths are provided in two paths: (1) a positive path starting from the load hot, passing through R3, D5, Q1, and R10 and ending at ground, and (2) a negative path starting from ground, passing through R11, Q2, D6, and R3 and ending at the load hot. Generally, due to the polarities of the diodes D5 and D6, when the line voltage is positive, the modulated current will flow through the positive path between the load hot terminal and the ground terminal, and when the line voltage is negative, it will flow through the negative path between the ground terminal and the load hot terminal.

[0044] Typically, during operation, the load hot terminal, load neutral terminal, and ground terminal of the tester circuit 200 are connected to the load hot terminal, load neutral terminal, and ground terminal of the GFCI wiring device socket, respectively, through the blades 104 inserted into the GFCI socket panel. However, in an alternative example, by connecting the load hot terminal of the tester circuit 200 to the GFCI load hot terminal and connecting the ground terminal of the tester circuit 200 to the GFCI line neutral terminal, the response of the GFCI wiring device to a forward polarity fault can be tested. Similarly, by connecting the load hot terminal of the tester circuit 200 to the GFCI line hot terminal and connecting the ground terminal of the tester circuit 200 to the GFCI load neutral terminal, the response to a reverse polarity fault can be tested.

[0045] It should be understood that within the range where the terminals of the tester circuit 200 are connected to the GFCI line hot terminal or the GFCI line neutral terminal, this connection cannot be created by inserting the blades into the socket face of the GFCI wiring device. Instead, the connection can be created by connecting to the terminals that are typically exposed on the side of the GFCI wiring device and are typically arranged within the wall box after installation. Thus, in this example, the forward polarity ground fault test or the reverse polarity ground fault test is typically completed before installation. For example, the forward or reverse polarity ground fault test can include tests performed by the manufacturer or a third party before selling the GFCI wiring device (e.g., during the manufacturing process) or by a technician or other user after the device is sold but before installation is completed (since the terminals located on the side of the device can be accessed before installation is completed).

[0046] First, turning to the operation of the positive path, during the positive half - cycle, the diode D5 is forward - biased, allowing leakage current to flow from the load hot terminal to the ground terminal. The magnitude of the leakage current is adjusted by the amount of current allowed by the switch Q1. That is, if Q1 is in the active state, the maximum amount of leakage current is allowed to flow through the positive path to the ground; while if Q1 is in the cutoff state, the minimum amount of leakage current flows through. Thus, by changing the voltage at the base (or gate, where Q1 is a FET) of Q1, the amount of leakage current can be modulated.

[0047] When Q1 is in the active state, R3 is the main maximum leakage current limiting component and R10 is secondary. The main use of R10 is as a current sensing resistor, and its output is compared by comparator 202, which consists of operational amplifier U1A and its associated components, resistors R6 and R8, with the output of waveform generator V1. (V1 can be implemented as a voltage controlled oscillator (VCO), or in an alternative example, as a bench-top waveform generator, or as any suitable circuit for generating the desired waveform.) As will be described in more detail below, the output of comparator 202 (which is input to switch Q1) changes to keep the voltage across resistor R10 equal to the output of waveform generator V1. Thus, the input to Q1 changes in a manner that modulates the leakage current such that it follows the waveform of waveform generator V1, i.e., the frequency of the leakage current is substantially equal to (i.e., within ±10 hz) the frequency of the output signal of waveform generator V1. Thus, the frequency of the leakage current can be set or adjusted according to the frequency of waveform generator V1.

[0048] More specifically, when a positive leakage current passes through resistor R10, the resulting voltage is measured by U1A at the inverting input. This leakage current sensing voltage is compared with the signal generated by waveform generator V1. If the leakage current detection voltage at resistor R10 is less than the output voltage of V1, the voltage output by U1A will increase. This can be seen at time t1 in Figure 3 : the output voltage of V1 increases, so the R10 leakage current sensing voltage is less than the V1 output voltage at time t1, and the output of U1A increases. This increase continues until the leakage current sensing voltage equals the output voltage of waveform generator V1, at which point the waveform generator output reaches a peak and starts to decrease. At time t2, the waveform generator V1 output signal decreases, so the leakage current sensing voltage at R10 is greater than the V1 output signal, causing the output of U1A to decrease. This decrease continues until the leakage current sensing voltage equals the V1 output voltage, at which point the V1 output voltage reaches a minimum and starts to increase. Thus, the operation of U1A serves to regulate the conductivity of BJT Q1 between the saturation and cut-off modes, i.e., typically regulated in the linear mode according to the respective values of V1 and the line voltage, so as to modulate the leakage current flowing between HOT and NEU during the positive half-cycle. In this way, the output of comparator 202 changes the input to switch Q1 such that the current through R10 follows the voltage waveform of waveform generator V1, thereby modulating the leakage current in a manner that follows the voltage waveform of waveform generator V1. For the purposes disclosed herein, "following" or "follows" means that the leakage current regenerates the shape of the waveform generator output signal as a proportional waveform.

[0049] The negative path (which again includes R11, Q2, D6, and R3) operates in the negative half - cycle in the same manner as the positive path in the positive half - cycle. That is, the comparator 204 adjusts the switch Q2 to modulate the leakage current flowing from the ground terminal to the load hot terminal such that the current through R11 follows the reverse voltage of the waveform generator V1. A secondary path is employed in this example because even though the output of the comparator 202 will be negative in the negative half - cycle, the switch Q1 (here an NPN BJT) will enter the cut - off state, blocking the leakage current flowing from the ground terminal to the load hot terminal. Thus, the negative path employs a PNP BJT that enters the active mode in response to the negative input voltage from the comparator 204. Note that, in addition to the polarity difference, an inverter 206 is included, which includes the operational amplifier U1C and its associated components, resistors R4 and R5, to invert the V1 output signal to make it compatible with the comparator 204.

[0050] Thus, during the positive half - cycle of the line voltage, the positive path is used to modulate the leakage current; while during the negative half - cycle, the negative path is used to modulate the leakage current. As Figure 3 shown, the net current through R3 is modulated during the positive half - cycle to form a sine wave with a positive offset (i.e., according to the waveform generator V1, the waveform will oscillate from 0 to some positive value), and is modulated to form a sine wave with a negative offset (i.e., according to the waveform generator V1, the waveform will oscillate from 0 to some negative value).

[0051] The amplitude of the leakage current (IF) can be selected by choosing the amplitude of V1 such that is the positive half - cycle, is the negative half - cycle. As described above, the frequency of the leakage current can be similarly selected by choosing the frequency of the waveform generator V1. In this way, the waveform generator V1 will actively control the properties of the leakage current, including frequency, amplitude, and shape (sine, sawtooth, square wave, aperiodic waveform, etc.).

[0052] The waveform generator V1 can be configured to automatically scan from the minimum frequency to the maximum frequency in order to test the GFCI wiring device at various frequencies, including frequencies higher than the fundamental frequency of the supply voltage. Alternatively, the user can select the frequency or other characteristics of the waveform generator V1 according to the user interface (such as buttons or a touch screen set on the outside of the housing 102).

[0053] The waveform generator as used in the present disclosure is capable of generating any desired arbitrary waveform, including, for example, non-sinusoidal and non-periodic waveforms. For example, waveform generator V1 can be configured to generate non-sinusoidal waveforms to simulate a harmful load (such as a vacuum cleaner) or an arc fault. For example, an arc fault can be simulated by creating a waveform that adds current peaks and / or "shoulders" to a sine wave. In combination with the present disclosure, it will be readily understood by those skilled in the art that various waveforms can be generated to simulate various harmful loads or arc faults.

[0054] In some examples, during testing, the magnitude of the leakage current can be set to be slightly lower than the trip threshold at one or more frequencies above the power frequency to ensure that the GFCI wiring device does not trip due to a leakage current value lower than the minimum value required by the standard. These same frequencies or different frequencies can be used to test leakage current values above the trip threshold to ensure that the value at which the GFCI wiring device trips is correct. Since the magnitude and frequency of the leakage current can be selected according to the magnitude and frequency of waveform generator V1, the user can select the desired frequency and leakage current for a particular test. This can be achieved through a user interface such as a connected computer or mobile device, or through buttons or a touch screen located on the tester itself. In some examples, the user can pre-load a particular test routine into a memory that tests the GFCI wiring device at the desired frequency and leakage current value. The test routine can be selected by pressing a button or can start automatically and run repeatedly when the tester is first turned on.

[0055] As used in the present invention, a comparator is any circuit adapted to produce an output based on a comparison between the output of waveform generator V1 and a value representative of the leakage current. Since the output of the comparator is input to switches (such as switches Q1, Q2) that change the magnitude of the current flowing through the leakage path, the value representative of the leakage current serves as a feedback signal to the comparator. In other words, the comparator acts together with switches Q1, Q2 to adjust the magnitude of the current through the leakage path, the magnitude of which is then input to comparator 202 as a value to be compared with the output of waveform generator V1. This function generally keeps switches Q1, Q2 in the linear region to appropriately modulate the leakage current according to the output of V1. Therefore, the comparator used in the present invention should not be limited to that class of operational amplifier topologies that do not have a feedback signal or that output only at the positive or negative rail of the operational amplifier based on the comparison of input signals. In fact, in various alternative examples, the comparator can take the form of an inverting or non-inverting amplifier or a differential amplifier operational amplifier topology.

[0056] Comparators 202 and 204 are powered by power supply circuits 208 and 210, which are functionally low-pass filters that generate a positive DC voltage V+ and a negative DC voltage V-. The operation of power supply circuits 208 and 210 will be generally understood and will not be described here. Additionally, power supply circuits 208 and 210 are provided only as examples of power supply circuits that can be used to generate the DC voltage inputs for comparators 202 and 204, and any suitable power supply circuit can be used.

[0057] As Figure 2 shown, the modulated leakage current does not follow a true sine wave but is offset according to each half-cycle. This is due to the way the leakage current modulates the line voltage, resulting in a completely positive waveform when the line voltage is positive and a completely negative waveform when the line voltage is negative. This can be resolved by fully rectifying the power supply voltage applied between the load hot terminal and the ground terminal of the tester. In this example, according to the half-cycle of the power supply voltage, the current does not alternate between positive and negative currents but remains positive or negative (depending on the rectification method) regardless of the half-cycle. Such an example eliminates the need for one of the leakage paths because Figure 2 provides two leakage paths to handle the two half-cycles. Thus, if a full-wave rectifier applies a completely positive voltage between the load hot terminal and the ground terminal, only a positive leakage path (e.g., the leakage path including components R3, Q1, and R10) and one comparator (e.g., comparator 202) need to be included because no negative current can act on the negative leakage path. Alternatively, if a full-wave rectifier applies a completely negative voltage between the load hot terminal and the ground terminal, only a negative leakage path (e.g., the leakage path including components R3, Q2, and R11) and one comparator (e.g., comparator 204) need to be included because no positive current can act on the positive leakage path.

[0058] Although several inventive embodiments have been described and illustrated herein with reference to certain exemplary embodiments, those skilled in the art will readily envision various other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each such variation and / or modification is to be regarded as within the scope of the inventive embodiments described herein (and those skilled in the art will understand that various detailed changes may be made therein without departing from the spirit and scope of the invention as defined by the claims, which can be supported by the written description and the drawings). More generally, those skilled in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are exemplary, and the actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications using the teachings of the invention. Through routine experimentation alone, those skilled in the art will recognize or be able to ascertain many equivalents to the specific inventive embodiments described herein. Accordingly, it should be understood that the foregoing embodiments are presented by way of example only and are within the scope of the appended claims and their equivalents. The embodiments of the invention may be practiced in a different manner than specifically described and claimed. In addition, when describing exemplary embodiments with reference to a certain number of elements, it will be understood that the exemplary embodiments may be implemented with fewer or more than a certain number of elements.

[0059] All reference documents cited herein, including publications, patent applications, and patents, are incorporated by reference into this application to the same extent as if each reference document were individually and specifically indicated to be incorporated by reference in its entirety into this application.

[0060] All definitions defined and used herein shall be understood to control dictionary definitions, definitions in the documents incorporated by reference, and / or the ordinary meaning of the defined terms.

[0061] In the context of describing the present invention (particularly in the context of the following claims), the use of the terms "a", "an", and "the" and similar referents shall be construed to cover both the singular and the plural unless otherwise stated herein or clearly contradicted by the context. The terms "comprising", "having", "including", and "containing" shall be construed as open-ended terms (i.e., meaning including but not limited to), unless otherwise specified. The term "connected" shall be understood to mean partially or wholly included, attached, or joined together, even if there is something intervening without direct attachment.

[0062] As used in this specification and the claims, the phrase "at least one" in reference to a list of one or more elements should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements, nor excluding any combinations of elements in the list of elements. This definition also allows that an element may optionally be present rather than an element explicitly identified in the list of elements to which the phrase "at least one" refers, whether or not those elements are related to the explicitly identified elements. Thus, as a non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B", or equivalently "at least one of A and / or B") may, in one embodiment, refer to at least one (optionally including more than one) A, with no B present (optionally including elements other than B); in another embodiment, at least one, optionally including more than one B, and no A present (and optionally including elements other than A); in yet another embodiment, at least one, optionally including more than one A, and at least one, optionally including more than one B (and optionally including other elements); and so on.

[0063] It should also be understood that, unless there is an express contrary indication, in any method claimed herein that includes a plurality of steps or acts, the order of the steps or acts need not be limited to the order of the steps or acts.

[0064] The specification and claims may use approximate language to modify any quantitative representation that allows for permissive variation without resulting in a change in the relevant function. Thus, a value modified by one or more terms such as "about" and "substantially" is not limited to the precise value specified. In at least some instances, the approximate language may correspond to the precision of the instrument used to measure the value. Throughout this specification and the claims, range limitations may be combined and / or interchanged. Such ranges will be identified and all sub-ranges subsumed therein will be included unless the context or language indicates otherwise.

[0065] References to a numerical range should be understood as a shorthand method of referring individually to each separate numerical value falling within that range, unless otherwise indicated, and each separate numerical value is incorporated in the specification as if it were individually recited.

[0066] All methods described herein may be performed in any suitable order, unless otherwise indicated or clearly in conflict. Unless otherwise indicated, any or all of the embodiments provided herein, or the exemplary language (e.g., "such as") should only be understood as better illustrating embodiments of the invention and not as limiting the scope of the invention.

[0067] No language in the specification should be construed as indicating that any non-claimed element is essential for the practice of this aspect.

[0068] In the claims and in the foregoing specification, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "consisting of," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" are to be respectively closed or semi-closed transitional phrases, as set forth in section 2111.03 of the United States Patent and Trademark Office's Manual of Patent Examining Procedure.

[0069] It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. It is not intended to limit the invention to the specific forms disclosed, but on the contrary, it is intended to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined by the appended claims. Accordingly, the invention is intended to cover modifications and variations of the invention falling within the scope of the appended claims and their equivalents.

Claims

1. A tester for a frequency-related ground fault interruption wiring device, comprising: A tester circuit, comprising: A switch disposed between a first terminal and a second terminal, wherein when a voltage is applied between the first terminal and the second terminal, a leakage current flows through a leakage path between the first terminal and the second terminal, and a magnitude of the leakage current is at least partially determined by a conductivity of the switch; A waveform generator configured to generate a waveform generator output signal; and A comparator configured to generate a comparator output signal based on a comparison between the waveform generator output signal and a current sensing signal representing the leakage current, wherein the conductivity of the switch is adjusted according to the comparator output signal such that the leakage current follows the waveform generator output signal.

2. The tester according to claim 1, wherein the waveform generator output signal is a periodic waveform having a frequency, and wherein the frequency of the waveform generator output signal is greater than the frequency of the voltage applied between the first terminal and the second terminal.

3. The tester according to claim 2, wherein the voltage applied between the first terminal and the second terminal is a power supply voltage.

4. The tester according to claim 1, further comprising a second switch disposed between the first terminal and the second terminal, wherein during the negative half-cycle of the voltage applied between the first terminal and the second terminal, a second leakage current flows through a second leakage path, and the magnitude of the second leakage current is at least partially determined by the conductivity of the second switch, and wherein during the positive half-cycle of the voltage applied between the first terminal and the second terminal, the leakage current flows through the leakage path.

5. The tester according to claim 4, further comprising a second comparator configured to generate a second comparator output signal based on a comparison of an inverted periodic output signal and a second current signal, the inverted periodic output signal being the inversion of the periodic output signal, the second current sensing signal representing the second leakage current, and wherein the conductivity of the second switch is adjusted according to the second comparator output signal such that the frequency of the second leakage current is substantially equal to the frequency of the waveform generator.

6. The tester according to claim 1, wherein the waveform generator includes a voltage-controlled oscillator.

7. The tester according to claim 1, wherein the waveform generator output signal is a periodic waveform having a frequency, and wherein the waveform generator is configured to change the frequency of the periodic output signal.

8. The tester according to claim 1, wherein the waveform generator is configured to change the magnitude of the waveform generator output signal.

9. The tester according to claim 1, wherein the waveform generator output signal is a non-sinusoidal output signal.

10. The tester according to claim 9, wherein the waveform generator output is non-periodic.

11. The tester according to claim 1, wherein the voltage applied between the first terminal and the second terminal is a full-wave rectified supply voltage.

12. The tester according to claim 1, wherein the first terminal is in electrical communication with the load hot terminal of the frequency-dependent ground fault interrupt wiring device, and the second terminal is in electrical communication with the ground terminal of the frequency-dependent ground fault interrupt wiring device.

13. The tester according to claim 12, wherein the tester circuit is disposed within a housing, and the housing includes a plurality of blades sized and arranged to engage a receptacle of the frequency-dependent ground fault interrupt wiring device, and the first terminal is in electrical communication with the load hot terminal through one of the plurality of blades that engages the load hot receptacle of the frequency-dependent ground fault interrupt wiring device, and the second terminal is in electrical communication with the ground terminal through one of the plurality of blades that engages the ground receptacle of the frequency-dependent ground fault interrupt wiring device.

14. The tester according to claim 1, wherein the first terminal is in electrical communication with the load hot terminal of the frequency-dependent ground fault interrupt wiring device, and the second terminal is in electrical communication with the line neutral terminal of the frequency-dependent ground fault interrupt wiring device.

15. The tester according to claim 1, wherein the first terminal is in electrical communication with the line hot terminal of the frequency-dependent ground fault interrupt wiring device, and the second terminal is in electrical communication with the load neutral terminal of the frequency-dependent ground fault interrupt wiring device.

16. A tester for a frequency-dependent ground fault interrupt wiring device, comprising: A tester circuit, comprising: A switch disposed between a first terminal and a second terminal, wherein when a voltage is applied between the first terminal and the second terminal, a leakage current flows through a leakage path between the first terminal and the second terminal, and a magnitude of the leakage current is at least partially determined by the conductivity of the switch; and A waveform generator configured to generate a waveform generator output signal, wherein the switch is driven to modulate the magnitude of the leakage current such that the leakage current follows the waveform generator output signal.

17. The tester according to claim 16, wherein the waveform generator output signal is a periodic waveform having a frequency, and the frequency of the waveform generator output signal is greater than the frequency of the voltage applied between the first terminal and the second terminal.

18. The tester according to claim 17, wherein the voltage applied between the first terminal and the second terminal is a supply voltage.

19. The tester according to claim 16 further includes a second switch disposed between the first terminal and the second terminal, wherein during a negative half-cycle of the voltage applied between the first terminal and the second terminal, a second leakage current flows through a second leakage path, and a magnitude of the second leakage current is at least partially determined by a conductivity of the second switch, and wherein during a positive half-cycle of the voltage applied between the first terminal and the second terminal, the leakage current flows through the leakage path.

20. The tester according to claim 16, wherein the waveform generator includes a voltage-controlled oscillator.

21. The tester according to claim 16, wherein the output signal of the waveform generator is a periodic waveform having a frequency, and wherein the waveform generator is configured to change a frequency of the periodic output signal.

22. The tester according to claim 21, wherein the waveform generator is configured to change a magnitude of the periodic output signal.

23. The tester according to claim 16, wherein the output signal of the waveform generator is a non-sinusoidal output signal.

24. The tester according to claim 23, wherein the output of the waveform generator is non-periodic.

25. The tester according to claim 16, wherein the voltage applied between the first terminal and the second terminal is a full-wave rectified supply voltage.

26. The tester according to claim 16, wherein the first terminal is in electrical communication with a load hot terminal of the frequency-dependent ground fault interruption wiring device, and the second terminal is in electrical communication with a ground terminal of the frequency-dependent ground fault interruption wiring device.

27. The tester according to claim 26, wherein the tester circuit is disposed within a housing, and wherein the tester includes a plurality of blades sized and arranged to engage a receptacle of the frequency-dependent ground fault interruption wiring device, and wherein the first terminal is in electrical communication with the load hot terminal through one of the plurality of blades that engages a load hot receptacle of the frequency-dependent ground fault interruption node device, and wherein the second terminal is in electrical communication with the ground terminal through one of the plurality of blades that engages a ground receptacle of the frequency-dependent ground fault interruption wiring device.

28. The tester according to claim 16, wherein the first terminal is in electrical communication with a load hot terminal of the frequency-dependent ground fault interruption wiring device, and the second terminal is in electrical communication with a line neutral terminal of the frequency-dependent ground fault interruption wiring device.

29. The tester according to claim 16, wherein the first terminal is in electrical communication with the line hot terminal of the frequency-dependent ground fault interruption wiring device, and the second terminal is in electrical communication with the load neutral terminal of the frequency-dependent ground fault interruption wiring device.

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