Current transformer assembly

Abstract

A current transformer for a ground fault circuit breaker (GFCI) may include an iron core having a closed loop shape, the iron core having a first side, a second side, and an iron core opening, and a sense coil wound around the iron core, the sense coil configured to be magnetically coupled to a plurality of conductors passing through the iron core opening. The current transformer may include a first magnetic shield disposed on a first side of the core over the sense coil, and a second magnetic shield disposed on a second side of the core over the sense coil.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of U.S. Non - Provisional Patent Application No. 18 / 125,116, filed on March 23, 2023, and U.S. Provisional Application No. 63 / 436,446, filed on December 30, 2022, the entire contents of which are incorporated herein by reference in their entirety. Technical field

[0003] The present disclosure relates to current transformers. Background art

[0004] Conventional current transformers (CTs) for determining ground faults may have non - uniform coils and experience asymmetric magnetic coupling with the relative positions of two or more conductors passing through the CT. This asymmetry can lead to false indications regarding the presence of a ground fault. For example, even though the currents on two lines may be substantially the same and should theoretically cancel out, a current is induced in the CT. Thus, even when there is actually no current mismatch between the conductors, the induced current on the CT sensing coil may falsely indicate the presence of a ground fault.

[0005] Such conventional methods and systems are generally considered satisfactory for their intended purposes. However, there is still a need for improvement in the art. The present disclosure provides a solution to this need. Summary of the invention

[0006] A current transformer for a ground - fault circuit interrupter (GFCI) can include a core having a loop shape and a sensing coil wound around the core. The loop shape has a first side, a second side, and a core opening, and the sensing coil is configured to be magnetically coupled to a plurality of conductors passing through the core opening. The current transformer can include a first magnetic shield disposed on the first side of the core above the sensing coil, and a second magnetic shield disposed on the second side of the core above the sensing coil.

[0007] In some embodiments, the loop shape can be a toroidal shape. For example, the first magnetic shield and the second magnetic shield are washer - shaped or complementary to the core shape.

[0008] The first magnetic shield and the second magnetic shield can be made of a ferromagnetic material (e.g., metal and / or alloy). The current transformer can include a housing configured to hold and / or enclose the first magnetic shield and the second magnetic shield with the core and the sensing coil.

[0009] In some embodiments, the current transformer can include a third magnetic shield having a conduit shape disposed in the core opening. The housing can include an inner wall extending into the core opening. The inner wall can be disposed between the sensing coil and the third magnetic shield.

[0010] The conduit shape of the third magnetic shield can have an eyelet shape including a flange portion and a neck. The neck can be inserted into the iron core opening. The flange can be used as an axial stop.

[0011] The housing can be made of an electrically insulating material (e.g., plastic). The housing can include an outer wall, wherein an inner wall can define an iron core hole having a shape complementary to the iron core and configured to receive the iron core therein. For example, the first magnetic shield can be disposed within the iron core hole. For example, the first magnetic shield can be disposed on and / or engaged (e.g., non-electrically adhered) to the sense coil (e.g., and the iron core).

[0012] The housing can define a shield hole separated from the iron core hole by a partition wall extending between the outer wall and the inner wall of the housing. The second magnetic shield can be disposed in the shield hole and separated from the sense coil and the iron core by the partition wall.

[0013] In some embodiments, the housing can be a single-piece material. In some embodiments, the housing can include a first portion and a second portion configured to be assembled together to enclose the iron core, the sense coil, and at least one of the first magnetic shield and the second magnetic shield.

[0014] In some embodiments, the first magnetic shield and the second magnetic shield can have different sizes. For example, the first magnetic shield and the second magnetic shield can have different inner diameters.

[0015] In some embodiments, the housing can define a plurality of terminal connectors including a first sense terminal and a second sense terminal operably connected to opposite ends of the sense coil. In some embodiments, the current transformer can include a test coil wound around a portion of the iron core together with the sense coil. The plurality of terminals can include a first test terminal and a second test terminal operably connected to opposite ends of the test coil. In some embodiments, the plurality of terminals can be aligned in the axial direction.

[0016] According to at least one aspect of the present disclosure, a GFCI can include a line conductor, a neutral conductor, and a current transformer. The current transformer can be any suitable current transformer, e.g., as described above. The line conductor and the neutral conductor can, for example, pass through the iron core opening. Any suitable number of conductors is contemplated herein.

[0017] According to at least one aspect of the present disclosure, a GFCI may include line conductors, neutral conductors, and current transformers, for example, as described above. The current transformer may include a sensing coil and a test coil wound around an iron core. The sensing coil is configured to be magnetically coupled to the line conductor and the neutral conductor passing through the opening of the iron core, and the test coil is wound around the iron core and is configured to be magnetically coupled to the sensing coil through the iron core to provide a test signal to the sensing coil. For example, the current transformer may include the first shield, the second shield, and / or the third shield as described above.

[0018] These and other features of the embodiments of the present disclosure will become more apparent to those skilled in the art from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Therefore, those skilled in the art to which the present disclosure pertains will readily understand how to manufacture and use the devices and methods of the present disclosure without undue experimentation. Embodiments thereof will be described in detail below with reference to certain drawings, wherein:

[0020] Figure 1A is a front view of an embodiment of a current transformer according to the present disclosure;

[0021] Figure 1B is Figure 1A a cross-sectional view of an embodiment of

[0022] Figure 1C is Figure 1A a rear view of an embodiment of

[0023] Figure 1D is Figure 1A a side view of an embodiment of

[0024] Figure 1E is Figure 1A a bottom view of an embodiment of

[0025] Figure 1F is a plan view of an embodiment of a wound iron core of an embodiment according to the present disclosure Figure 1A of

[0026] Figure 2A is a perspective view of another embodiment of a current transformer according to the present disclosure;

[0027] Figure 2B is Figure 2A a front view of an embodiment of

[0028] Figure 2C is Figure 2A a cross-sectional view of an embodiment of

[0029] Figure 2D is Figure 2ARear perspective view of an embodiment;

[0030] Figure 2E is Figure 2A Bottom view of an embodiment;

[0031] Figure 2F is Figure 2A Top view of an embodiment;

[0032] Figure 2G is Figure 2A Side view of an embodiment;

[0033] Figure 2H is Figure 2A Side view of an embodiment;

[0034] Figure 2I is Figure 2A Front perspective view of an embodiment;

[0035] Figure 2J is Figure 2A Front view of an embodiment, showing a part of the housing and the magnetic shield removed to expose the iron core with the sensing coil thereon;

[0036] Figure 2K Perspective view of an embodiment of the sensing coil and the test coil wound around the iron core;

[0037] Figure 2L shows Figure 2A Exploded front view of an embodiment;

[0038] Figure 2M shows Figure 2A Perspective exploded view of an embodiment;

[0039] Figure 2N shows Figure 2A Front view of an embodiment with the housing removed;

[0040] Figure 2O shows Figure 2O Cross-sectional view of the view shown;

[0041] Figure 3A is Figure 2A Perspective view of an embodiment of a ground fault circuit interrupter in an embodiment in which

[0042] Figure 3B is Figure 3A Partial plan view of an embodiment;

[0043] Figure 3C is Figure 3A Partial front perspective view of an embodiment;

[0044] Figure 3DYes Figure 3A Partial rear perspective view of an embodiment of

[0045] Figure 4 Shows a comparison of coil distributions, showing a uniform distribution on the left and three different types of non-uniform coils around a toroidal magnet core;

[0046] Figure 5 Is a schematic diagram of an arrangement with a current transformer having a non-uniform coil wound around a core, and three conductors passing through the core opening also causing a winding effect;

[0047] Figure 6 Is Figure 5 Perspective view of an arrangement of , showing a first magnetic shield and a second magnetic shield;

[0048] Figure 7 Is a schematic diagram of an embodiment of a test structure for evaluating the effect of coil distribution;

[0049] Figure 8 Is a schematic diagram of an embodiment of a test structure for evaluating the coil distribution effect and the surrounding effect;

[0050] Figure 9 Shows Figure 8 Cross-sectional view of an embodiment of in use, showing probe rotation and double-conductor positions within the current transformer at four different locations;

[0051] Figure 10 Shows experimental results plotted for comparing an unshielded current transformer with a shielded current transformer according to the present disclosure, each showing the relationship of voltage to time using the rotation and arrangement shown in Figure 9 ;

[0052] Figure 11 Is a schematic diagram of an embodiment of a GFCI having a current transformer with a single core and multiple coils, where both ground fault detection and grounded neutral detection operate on the sense coil, and a test signal is sent on the test coil;

[0053] Figure 12 Shows Figure 11 Embodiment of a circuit diagram of an embodiment of ; and

[0054] Figure 13 Shows an embodiment of a test signal scheme using Figure 11 and Figure 12 of an embodiment, showing the use of a microprocessor to generate a waveform that will be sent through the test coil and coupled to the sense coil to be received by a test detection module to determine that a test has occurred and / or whether the GFCI is operating properly. DETAILED DESCRIPTION

[0055] Reference will now be made to the accompanying drawings, in which like reference numerals identify similar structural features or aspects of the present disclosure. For purposes of explanation and illustration and not limitation, illustrative views of embodiments of current transformers in accordance with the present disclosure are shown in Figure 1A and Figure 2A and are generally designated by reference numerals 100 and 200, respectively. Other embodiments and / or aspects of the present disclosure are shown in Figure 1B - 1F and 2B-13.

[0056] Referring to Figures 1A to 2O , current transformers 100, 200 for a ground fault circuit interrupter (GFCI) (e.g., as shown in Figures 3A to 3D ) may include a core 101 having a loop shape (e.g., a closed loop shape, a segmented loop shape, a toroidal shape, an annulus, a square toroidal shape) (e.g., as shown in Figure 1F ), which has a first side 101a, a second side 101b, and a core opening 101c. The current transformers 100, 200 may include a sensing coil 103 wound around the core 101, the sensing coil 103 being configured to be magnetically coupled to a plurality of conductors (e.g., at least a line conductor and a neutral conductor) passing through the core opening 101c.

[0057] The current transformers 100, 200 may include a first magnetic shield 105, 205 disposed on the first side 101a of the core 101 above the sensing coil 103 (e.g., not in electrical communication with the sensing coil 103 or the core 101). The current transformers 100, 200 may include a second magnetic shield 107, 207 disposed on the second side 101b of the core 101 above the sensing coil 103 (e.g., not in electrical communication with the sensing coil 103 or the core 101). The core 101 may be made of any suitable current transformer core material (e.g., nanocrystalline material).

[0058] In some embodiments, the loop shape may be, for example, a toroidal shape. The loop shape may be any suitable shape that causes a magnetic circuit. For example, the first magnetic shields 105, 205 and the second magnetic shields 107, 207 may be washer-shaped (e.g., circular with flat sides) or otherwise complementary shaped to the core 101. In some embodiments, the first magnetic shields 105, 205 and the second magnetic shields 107, 207 may be ellipsoidal in shape, and / or any other shape conformal to the core shape.

[0059] The first magnetic shields 105, 205 and the second magnetic shields 107, 207 may be made of a ferromagnetic material (e.g., a metal and / or an alloy). Any other suitable magnetic shielding material is contemplated herein.

[0060] The current transformer 100 may include housings 109, 209 configured to hold and / or enclose a first magnetic shield 105, 205 and a second magnetic shield 107, 207 with a core 101 and a sensing coil 103.

[0061] The housings 109, 209 may be made of an electrically insulating material (e.g., plastic). The housings 109, 209 may include outer walls 111a, 211a and inner walls 111b, 211b that define core holes 113, 213 having a shape complementary to the core 101 (e.g., including the sensing coil 103 wound therearound) and are configured to receive the core 101 therein (e.g., where the sensing coil 103 is wound around the core 101). For example, the inner walls 111b, 211b may form a tubular shape onto which the wound cores 101, 103 may be inserted. The inner walls 111b, 211b may extend into the core opening 101c.

[0062] For example, the first magnetic shields 105, 205 may be disposed within the core holes 113, 213. For example, the first magnetic shields 105, 205 may be disposed on and / or joined to the sensing coil 103 (e.g., and the core 101). In some embodiments, the first magnetic shields 105, 205 and the second magnetic shields 107, 207 may be bonded within the housings 109, 209 using a material 114 (e.g., an adhesive, a thermoplastic, etc.), as Figure 1B shown. In some embodiments, the material 114 may be non-conductive and provide an electrical barrier. Any other suitable method of holding the magnetic shields 105, 205, 107, 207 within the housings 109, 209 (e.g., and / or against the wound cores 101, 103) is contemplated herein.

[0063] The housings 109, 209 may define shield holes 115, 215 separated from the core holes 113, 213 by partition walls 117, 217 extending between the outer walls 111a, 211a and the inner walls 111b, 211b of the housings 109, 209. The second magnetic shields 107, 207 may be disposed in the shield holes 115, 215 and separated from the sensing coil 103 and the core 101 by the partition walls 117, 217. In some embodiments, the housing 109 may be a single-piece material, e.g., as Figure 1A shown in the embodiment of. In some embodiments, the second magnetic shields 107, 207 may first be inserted into the core holes 113, after which an insulating washer may be added, and then the core 101 may be inserted. Any other suitable arrangement of insulating and holding the shields from the core 101 is contemplated herein.

[0064] In some embodiments, for example, as shown in the embodiment of Figure 2A , the housing 209 may include a first portion 209a and a second portion 209b, which are configured to be assembled together to contain the iron core 101, the sensing coil 103, and at least one of the first magnetic shield 205 and the second magnetic shield 207 (e.g., enclosing the first magnetic shield 205 as shown in the embodiment of Figure 2A ). For example, the first portion 209a may be the main body portion, and the second portion 209b may be a cover (e.g., via clips 218a and openings 218b) clipped onto the main body portion to enclose the wound iron core 101, 103, and the first magnetic shield 205. In some embodiments, the first portion 209a may form an outer wall 211a, an inner wall 211b, an iron core hole 213, and a shield hole 215.

[0065] In some embodiments, the current transformers 100, 200 may include third magnetic shields 119, 219 having a conduit shape disposed in the iron core opening 101c. For example, the inner walls 111b, 211b may be disposed between the sensing coil 103 and the third magnetic shields 119, 219 (e.g., when assembled as shown in Figure 1B and 2C ). The conduit shape of the third magnetic shields 119, 219 may have an eyelet shape including a flange portion and a neck, for example, as shown in the figure. As shown in the figure, the neck may be inserted into the iron core opening 101c. For example, the flange may be used as an axial stopper. The third magnetic shields 119, 219 may be made of any suitable material (e.g., similar to the first magnetic shields 105, 205 and / or the second magnetic shields 107, 207).

[0066] In some embodiments, the first magnetic shield 205 and the second magnetic shield 207 may have the same size. In some embodiments, the first magnetic shield 205 and the second magnetic shield 207 may have different sizes, for example, as shown in the embodiment of ... Figure 2A . For example, the first magnetic shield 205 and the second magnetic shield 207 may have different inner diameters (e.g., the second magnetic shield 207 may have a larger inner diameter than the first magnetic shield 205, as shown in the figure). Any suitable size for generating the desired shielding is contemplated herein.

[0067] In some embodiments, the housings 109, 209 may define a plurality of terminal connectors 121, 221, including first sensing terminals 121a, 221a and second sensing terminals 121b, 221b operably connected to opposite ends 103a, 103b of the sensing coil 103. In some embodiments, for example, as shown in Figure 2AAs shown in the embodiments, the current transformer 200 may include a test coil 223 (e.g., as shown in Figure 2K and 2N ). The test coil 223 is wound around a portion of the iron core 101 together with the sensing coil 103. The plurality of terminals 221 may include a first test terminal 221c and a second test terminal 221d operatively connected to opposite ends 223a, 223b of the test coil 223. In some embodiments, the plurality of terminals 221 may be aligned in the axial direction, e.g., in a row extending radially from the housing 209 as shown.

[0068] According to at least one aspect of the present disclosure, with further reference to Figures 3A - 3D , the GFCI 300 may include a first conductor 301 (e.g., a line, neutral, or ground wire), a second conductor 303 (e.g., a line, neutral, or ground wire), and a current transformer. The current transformer may be any suitable current transformer, such as the 200 described above. The first conductor 301 and the second conductor 303 may pass through the core opening 101c, for example. Any suitable number of conductors (e.g., three as shown) for any suitable application is contemplated herein. According to at least one aspect of the present disclosure, the GFCI may include a line conductor, a neutral conductor, and a current transformer, e.g., as described above. The current transformer may include a sensing coil 103 wound around the iron core 101, and the sensing coil 103 is configured to be magnetically coupled to the line conductor and the neutral conductor passing through the core opening 101c. The GFCI may include a test coil 223 wound (e.g., partially) around the iron core 101 and configured to be magnetically coupled to the sensing coil 103 through the iron core 101 to provide a test signal to the sensing coil 103. For example, the current transformer 200 may include the first shield, the second shield, and / or the third shield as described above.

[0069] Figure 4 A comparison of coil distributions is shown, which shows a uniform distribution on the left and three different types of non-uniform coils around the toroidal core. Figure 5 is a schematic diagram of an arrangement with a current transformer having a coil (e.g., non-uniform or uniform) wound around an iron core, and the passage of three conductors through the core opening also causes a winding effect. Figure 6 is Figure 5 a perspective view of the arrangement of

[0070] Figure 7 showing a first magnetic shield and a second magnetic shield. Figure 8It is a schematic diagram of an embodiment of a test structure for evaluating coil distribution effects and surrounding effects. For example, two conductors can be offset from the center of a current transformer, and there can be a bent conductor outside the current transformer to provide a winding effect. Figure 9 Shows in use Figure 8 A cross-sectional view of an embodiment, showing probe rotation and dual conductor positions within a current transformer at four different locations.

[0071] Figure 10 Shows experimental results plotted for comparing an unshielded current transformer with a shielded current transformer according to the present disclosure, each showing the relationship of voltage to time using the Figure 9 Rotation and arrangement shown. As shown, shielding the current transformer with a first magnetic shield, a second magnetic shield, and a third magnetic shield results in a reduction in peak voltage attributed to non-uniform coils and surrounding effects. The results are less than the maximum value of 0.1 mV shown, while being higher than the maximum value of 0.1 mV without shielding. The results show a significant percentage reduction in peak voltage, independent of the set maximum value. Any other suitable maximum value is contemplated herein.

[0072] Figure 11 Shows a schematic diagram of an embodiment of a GFCI having a current transformer with a single iron core and multiple coils. Ground fault detection and grounded neutral detection are shown to both operate on a sensing coil, and a test signal is sent on a test coil magnetically coupled to the sensing coil. Figure 12 Shows Figure 11 An embodiment of a circuit diagram of an embodiment. Figure 13 Shows using Figure 11 And Figure 12 An embodiment of a test signal scheme of an embodiment, showing the use of a microprocessor to generate a waveform that will be sent through the test coil and coupled to the sensing coil to be received by a test detection module to determine that a test has occurred and / or whether the GFCI is operating properly.

[0073] According to the present disclosure, coil distribution is defined by how the coils geometrically rotate around the iron core. An unbalanced coil is when there are more or fewer turns around a particular part of the iron core, and due to this asymmetry, this can lead to improper current in the sensing coil. This unwanted current can be further exacerbated by conductors outside the current transformer that cause surrounding effects (e.g., the field of a conductor outside the current transformer that induces current in the sensing coil). Embodiments can include magnetic shielding to mitigate these effects. For example, embodiments can include two washer-shaped shields and an inner diameter insert for further shielding. The inner diameter insert can be used for load transfer applications, such as whenever there are different magnetic fields from parallel lines passing through the current sensor, such that the inner diameter insert can mitigate the effects of non-concentric lines.

[0074] Embodiments of the method may include one or more of the following: fixing a wound iron core (such as 101, 103) to the housing with a material (such as an adhesive, plastic, or any other suitable retainer), orienting the iron core such that when it is installed in the housing, the termination lead comes from the outer diameter and the start lead comes from the inner diameter, routing the start lead along the corner and away from the termination lead pin, routing the termination lead above and away from the start lead such that the start and termination leads should not touch, assembling a first shield into the housing above the inner wall of the housing (such as a tube), assembling a second shield onto the inner wall tube until it sits against the wound iron core, and / or fixing the first shield and the second shield to the ends of the iron core 101 using a thin bead material applied to the outer edge of the iron core 101. Embodiments of the method may include soldering the terminals (such as and then testing according to set specifications). After the terminals are soldered and set, the embodiment may have a minimum force of 4 pounds to move the pins. The leads may be provided with stress relief and may be coated from the housing to the pins with a suitable material. For example, an embodiment of the method may include pressing a third shield into the housing until the bottom of the flange of the shield is set on the face of the housing. The wire may have a visible strain relief loop. Embodiments of the method may include fixing the third shield to the housing with a material, such as as described above. For example, the position of the start / termination leads of the sense coil may be determined by the coil position that produces the lowest coil distribution test result.

[0075] Certain embodiments may include a dual - coil, shielded ground - fault current transformer. The magnetic influence of the current path on the current transformer output voltage can be controlled by using a magnetic shield near the sensor. Such a shield can face the current path and capture stray magnetic flux or unwanted energy.

[0076] Certain embodiments may include a magnetic shield structure for a toroidal transformer. Certain embodiments may include two or three magnetic shield structures that exert a high shielding effect on the magnetic flux generated by the current path. Certain embodiments may reduce inconsistent detection of ground faults under handle rated load conditions. Certain embodiments may include clamping a wound iron core between two iron washers to reduce the unintended flux interaction between the primary current path and the wound iron core (such as a nanocrystalline core wrapped with copper wire).

[0077] Certain embodiments may include a sense coil having many turns (such as approximately 176 turns). The coil distribution can be defined as the geometric distribution of the total number of turns around the iron core of the transformer (such as around 360°). Figure 4 A side - by - side comparison of different coil distributions is shown. The surrounding effect can be defined as the magnetic influence of nearby conductors (the surrounding effect). Figure 5 The winding effect from the conductors associated with the current transformer is shown.

[0078] The random distribution of the number of turns of the coil combined with the winding effect results in an output voltage Vout, the amplitude of which is different from zero. Compared with the ideal case (e.g., uniform coil distribution), the output voltage Vout has a significantly higher value. Vout is the result of the sum of the induced currents per turn (each turn having a positive or negative amplitude), and the contribution of each turn highly depends on its physical position around the iron core and relative to the line conductors (L1 and L2) or the neutral (N) conductor. To reduce the influence of nearby conductors, embodiments may include a shield of a washer-shaped high-permeability material (e.g., steel or high-permeability alloy).

[0079] The coil distribution screening has the purpose of verifying the output voltage deviation of the sensor (such as the quantization of the amplitude in a randomly distributed coil being ≠0) in the presence of a balanced 60A current flowing out and returning through the center of the current transformer (current loop). The surrounding effect screening simulates the effect of the current path on the current transformer (CT).

[0080] As described above regarding Figures 7 - 10 shown, the eccentric probe with two conductors rotates and generates an electromagnetic effect on the CT. Due to the randomly asymmetric coil, the CT changes its output voltage at any time according to the position of the conductor. This screening has the possibility of simultaneously checking the coil distribution and the winding effect on the CT. Then, the process can find the maximum value during a 360° rotation and check if it is below a defined limit (e.g., 0.1mV as shown in Figure 10 shown) and restart if so. Figure 10 It is shown that the CT equipped with a magnetic shield performs significantly better than the CT without a shield, and the difference between the peak and valley values and the amplitude of the highest peak are reduced. Embodiments may also have a dual coil on a shared iron core and retain the benefits of the shield.

[0081] Certain embodiments may include a magnetic shield for the ground fault protection iron core. The magnetic shield can reduce interference from unwanted flux sources that interfere with accurate ground fault detection. As shown in Figure 11 the embodiments shown may also include a push test signal decoupling function, which is more controllable and repeatable and has a lower possibility of field inconsistency due to a continuous ground fault. As shown in Figures 12 - 13As shown, embodiments may include a self - test method controlled and generated by a microcontroller. Embodiments can reduce the likelihood that the self - test function is affected by external factors because it can be controlled by a microcontroller and applied through an additional CT coil. Embodiments can provide increased protection against magnetic interference caused by manufacturing inconsistencies and changes in wire path routing, as well as increased consistency in field performance due to low - level persistent ground faults. In certain embodiments, the additional test coil makes the self - test function of the ground - fault detection circuit independent of voltage, frequency, and current, making the function more controllable and repeatable, with a lower likelihood of field inconsistencies due to long - term ground faults.

[0082] Embodiments may include any suitable computer hardware and / or software modules to perform any suitable functions (e.g., as disclosed herein). As will be understood by those skilled in the art, aspects of the present disclosure may be embodied as a system, method, or computer program product. Thus, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which possibilities may be referred to herein as a "circuit", "module", or "system". A "circuit", "module", or "system" may include one or more portions of one or more separate physical hardware and / or software components that may together perform the disclosed functions of the "circuit", "module", or "system", or a "circuit", "module", or "system" may be a single self - contained unit (e.g., of hardware and / or software). Additionally, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer - readable media having computer - readable program code embodied thereon.

[0083] Any combination of one or more computer - readable media may be utilized. A computer - readable media may be a computer - readable signal medium or a computer - readable storage medium. A computer - readable storage medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non - exhaustive list) of the computer - readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read - only memory (ROM), an erasable programmable read - only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read - only memory (CD - ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer - readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0084] A computer-readable signal medium may include a propagated data signal having computer-readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including but not limited to electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0085] The program code embodied on the computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wired, fiber optic cable, RF, etc., or any suitable combination of the foregoing.

[0086] The computer program code for performing the operations of the aspects of the present disclosure may be written in any combination of one or more programming languages, including object-oriented programming languages such as Java, Smalltalk, C++, etc., and conventional procedural programming languages such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter case, the remote computer may be connected to the user's computer through any type of network connection, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0087] Aspects of the present disclosure may be described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each block of any flowchart and / or block diagram, and combinations of blocks in any flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing apparatus create means for implementing the functions / acts specified in one or more blocks of any flowchart and / or block diagram.

[0088] These computer program instructions may also be stored in a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other device to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions for implementing the functions / acts specified in one or more blocks of the flowchart and / or block diagram.

[0089] Computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer-implemented process such that the instructions executed on the computer or other programmable apparatus provide a process for implementing the functions / acts specified herein.

[0090] Those of ordinary skill in the art will understand that any numerical values disclosed herein can be exact values or values within a range. Additionally, any approximate terms used in this disclosure (e.g., "about", "approximately", "substantially") can represent the values within the range. For example, in certain embodiments, the range can be within (plus or minus) 20%, or within 10%, or within 5%, or within 2%, or within any other suitable percentage or number as understood by those of ordinary skill in the art (e.g., for known tolerance limits or error ranges).

[0091] Unless the context clearly dictates otherwise, the articles "a", "an", and "the" as used in this specification and the appended claims are used herein to refer to one or more than one (i.e., at least one) grammatical object of the article. For example, "an element" means one element or more than one element.

[0092] As used herein in the specification and claims, the phrase "and / or" should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are present conjointly in some cases and separately in other cases. Multiple elements listed with "and / or" should be construed in the same manner, i.e., "one or more" of the elements so conjoined. Other elements may optionally exist in addition to the elements specifically identified by the "and / or" clause, whether related or unrelated to the elements specifically identified. Thus, as a non-limiting example, when used in conjunction with open-ended language such as "comprising", a reference to "A and / or B" can, in one embodiment, refer to only A (optionally including elements other than B); in another embodiment, only to B (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); and so on.

[0093] As used herein in the specification and claims, "or" shall be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be interpreted as inclusive, i.e., including at least one of a plurality of elements or a list of elements, but also including more than one, and optionally, additional unlisted items. Only terms that explicitly indicate the contrary, such as "only one of... " or "exactly one of... ", or when used in a claim, "consisting of... " will refer to including exactly one element of a plurality of elements or a list of elements. Generally, when preceded by an exclusive term (e.g., "either", "one of... ", "only one of... " or "exactly one of... "), the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e., "one or the other but not both").

[0094] As would be understood by one of ordinary skill in the art in view of the present disclosure, any suitable combination of any disclosed embodiment and / or any suitable portion thereof is contemplated herein.

[0095] The embodiments of the present disclosure described above and shown in the figures provide improvements in their respective fields. While the subject matter disclosed includes reference to certain embodiments, those skilled in the art will readily understand that changes and / or modifications can be made thereto without departing from the spirit and scope of the subject matter disclosed.

Claims

1. A current transformer for a ground fault circuit interrupter (GFCI), comprising: an iron core having a loop shape, the iron core having a first side, a second side, and a core opening; a sensing coil wound around the core, the sensing coil being configured to magnetically couple to a plurality of conductors passing through the core opening; a first magnetic shield disposed on a first side of the core above the sensing coil; and A second magnetic shield is disposed on the second side of the core above the sensing coil. The current transformer according to claim 1 , wherein the closed loop is in the shape of a ring. 3 . The current transformer according to claim 1 , wherein the first magnetic shield and the second magnetic shield are in a washer shape or a shape complementary to the core. 4 . The current transformer according to claim 3 , wherein the first magnetic shield and the second magnetic shield are made of ferromagnetic material. 5 . The current transformer according to claim 1 , further comprising a housing configured to hold and / or surround the first magnetic shield and the second magnetic shield with the core and the sensing coil. 6 . The current transformer according to claim 5 , further comprising a third magnetic shield having a conduit shape provided in the core opening. 7 . The current transformer of claim 6 , wherein the housing includes an inner wall extending into the core opening, wherein the inner wall is disposed between the sensing coil and the third magnetic shield. 8 . The current transformer according to claim 7 , wherein the conduit shape of the third magnetic shield is an eyelet shape including a flange portion and a neck portion.

9. The current transformer of claim 8, wherein the neck is inserted into the core opening, wherein the flange serves as an axial stop.

10. The current transformer according to claim 5, wherein the housing is made of an electrically insulating material.

11. The current transformer of claim 10, wherein the housing comprises an outer wall and an inner wall, the inner wall defining a core aperture having a shape complementary to the core and configured to receive the core therein. 12 . The current transformer according to claim 11 , wherein the first magnetic shield is disposed in the core hole. 13 . The current transformer according to claim 12 , wherein the first magnetic shield is provided on and / or joined to the sensing coil.

14. The current transformer of claim 13 , wherein the housing defines a shield hole, the shield hole being separated from the core hole by a partition wall extending between an outer wall and an inner wall of the housing, wherein the second magnetic shield is disposed in the shield hole and is separated from the sensing coil and the core by the partition wall.

15. A current transformer according to claim 14, wherein the housing is a single piece of material.

16. The current transformer according to claim 14, wherein the housing includes a first part and a second part, and the first part and the second part are configured to be assembled together to accommodate the iron core, the sensing coil, and at least one of the first magnetic shield and the second magnetic shield.

17. The current transformer according to claim 11, wherein the first magnetic shield and the second magnetic shield have different sizes, and wherein the first magnetic shield and the second magnetic shield have different inner diameters.

18. The current transformer according to claim 5, wherein the housing defines a plurality of terminal connectors, and the plurality of terminal connectors include a first sensing terminal and a second sensing terminal operatively connected to opposite ends of the sensing coil.

19. The current transformer according to claim 18, further comprising a test coil wound around a portion of the iron core together with the sensing coil, and wherein the plurality of terminals include a first test terminal and a second test terminal operatively connected to opposite ends of the test coil.

20. The current transformer according to claim 19, wherein the plurality of terminals are aligned in the axial direction.

21. A ground fault circuit interrupter (GFCI) comprising: a line conductor; a neutral conductor; and a current transformer including: an iron core having a closed-loop shape, the iron core having a first side, a second side, and an iron core opening, wherein the line conductor and the neutral conductor pass through the iron core opening; a sensing coil wound around the iron core, the sensing coil being configured to be magnetically coupled to the line conductor and the neutral conductor passing through the iron core opening; a first magnetic shield disposed on the first side of the iron core above the sensing coil; and a second magnetic shield disposed on the second side of the iron core above the sensing coil.

22. A ground fault circuit interrupter (GFCI) comprising: a line conductor; a neutral conductor; and a current transformer including: an iron core having a closed-loop shape, the iron core having a first side, a second side, and an iron core opening, wherein the line conductor and the neutral conductor pass through the iron core opening; a sensing coil wound around the iron core, the sensing coil being configured to be magnetically coupled to the line conductor and the neutral conductor passing through the iron core opening; and a test coil wound around the iron core and configured to be magnetically coupled to the sensing coil through the iron core to provide a test signal to the sensing coil.

23. The GFCI according to claim 22, further comprising: a first magnetic shield disposed on the first side of the iron core above the sensing coil; and a second magnetic shield disposed on the second side of the iron core above the sensing coil.

24. The GFCI according to claim 22, further comprising a third magnetic shield having a conduit shape and disposed in the iron core opening.

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