System and apparatus for ground fault detection using current measuring coils

Abstract

The present invention relates to a system and method for ground fault detection using current measuring coils. A system for current measurement and ground fault detection is disclosed. In an embodiment, the system includes a plurality of phase current measuring coils configured to detect phase currents associated with at least a portion of a multi-phase system. The system also includes a plurality of phase current measurement circuits connected to the phase current measurement coils and a ground fault detection circuit. The phase current measurement circuits are configured to measure the phase currents detected by the phase current measurement coils, and the ground fault detection circuit is configured to measure the sum of the phase currents detected by the phase current measurement coils.

Description

Background Art

[0001] An oven (or any other device) may employ current measuring coils to measure the current through the respective phases of a multi-phase system that powers one or more components of the oven. These coils effectively implement a transformer that divides the current by a fixed factor. The lower current can then be fed through a resistor (optionally with a rectifier in front), and the voltage across the resistor is then an indication of the current flowing.

[0002] Older ovens utilize only current measurement per power phase. In newer ovens it may be advantageous to also implement a ground fault detection system / circuitry to detect current leakage, for example through the chassis. Summary of the invention

[0003] In one aspect, embodiments of the inventive concepts disclosed herein are directed to a system for current measurement and ground fault detection. In an embodiment, the system includes a plurality of phase current measurement coils configured to detect phase currents associated with at least a portion of a multi-phase system. The system also includes a plurality of phase current measurement circuits connected to the phase current measurement coils and a ground fault detection circuit. The phase current measurement circuits are configured to measure the phase currents detected by the phase current measurement coils, and the ground fault detection circuit is configured to measure the sum of the phase currents detected by the phase current measurement coils.

[0004] On the other hand, embodiments of the inventive concepts disclosed herein are directed to a device including a circuit system for current measurement and ground fault detection. In an embodiment, the device includes one or more components powered by a multi-phase system. The device also includes a plurality of phase current measurement coils configured to detect phase currents associated with at least a portion of the multi-phase system. The device also includes a plurality of phase current measurement circuits connected to the phase current measurement coils and a ground fault detection circuit. The phase current measurement circuit is configured to measure the phase current detected by the phase current measurement coils, and the ground fault detection circuit is configured to measure the sum of the phase currents detected by the phase current measurement coils.

[0005] In another aspect, embodiments of the inventive concepts disclosed herein are directed to a method of current measurement and ground fault detection. In an embodiment, the method includes the following steps: detecting phase currents with a plurality of phase current measuring coils; measuring the phase currents detected by the phase current measuring coils with a plurality of phase current measuring circuits; and measuring the sum of the phase currents detected by the phase current measuring coils with a ground fault detection circuit.

[0006] This summary is provided merely as an introduction to the subject matter that is fully described in the detailed description and accompanying drawings. This summary should not be considered to describe essential features, nor should it be used to determine the scope of the claims. Moreover, it should be understood that both the foregoing summary and the following detailed description are merely examples and explanations and do not necessarily limit the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Embodiments of the inventive concepts disclosed herein may be better understood when considering the following detailed description. Such description refers to the included drawings, which are not necessarily drawn to scale and in which some features may be enlarged and some features may be omitted or may be schematically represented for clarity. Like reference numerals in the drawings may represent and refer to the same or similar elements, features, or functions. In the drawings:

[0008] Figure 1 is a block diagram illustrating a device including circuitry for current measurement and ground fault detection according to an example embodiment of the present disclosure;

[0009] Figure 2 is a schematic diagram of a system / circuitry system for current measurement and ground fault detection according to an exemplary embodiment of the present disclosure;

[0010] Figure 3 According to an embodiment of the present disclosure Figure 2 A schematic diagram of a phase current measurement circuit of the system / circuit system shown;

[0011] Figure 4 According to an exemplary embodiment of the present disclosure Figure 2 A schematic diagram of a ground fault detection circuit of the system / circuitry system shown; and

[0012] Figure 5 is a flow chart illustrating an example implementation of a method of current measurement and ground fault detection. DETAILED DESCRIPTION

[0013] Before explaining in detail at least one embodiment of the inventive concept disclosed herein, it should be understood that the application of the inventive concept is not limited to the details of the arrangement of the construction and components or steps or methods set forth in the following description or shown in the accompanying drawings. In the following detailed description of the embodiments of the inventive concept, many specific details are set forth in order to provide a more thorough understanding of the inventive concept. However, it is obvious to those of ordinary skill in the art who benefit from the present disclosure that the inventive concept disclosed herein can be practiced without these specific details. In other examples, well-known features may not be described in detail to avoid unnecessarily complicating the present disclosure. The inventive concept disclosed herein can have other embodiments, or can be practiced or executed in various ways. Moreover, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered restrictive.

[0014] As used herein, a letter following a reference numeral is intended to indicate an embodiment of a feature or element that may be similar but not necessarily identical to a previously described element or feature with the same reference numeral (e.g., 1, 1a, 1b). Such shorthand notation is used only for convenience and should not be construed as limiting the inventive concepts disclosed herein in any way unless expressly stated to the contrary.

[0015] In addition, unless expressly stated to the contrary, "or" refers to an inclusive "or" rather than an exclusive "or". For example, one of the following conditions satisfies condition A or B: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) or B is true (or exists), and both A and B are true (or exist).

[0016] In addition, "a" or "an" is used to describe the elements and components of the embodiments of the inventive concept. This is done only for convenience and to give a general meaning of the inventive concept, and "a" and "an" are intended to include one or at least one, and the singular also includes the plural, unless it is obvious that it means otherwise.

[0017] Finally, as used herein, any reference to "one embodiment" or "some embodiments" means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the inventive concept disclosed herein. The phrase "in some embodiments" appearing in various places in the specification is not necessarily all referring to the same embodiment, and embodiments of the disclosed inventive concept may include any combination of one or more features expressly described or inherently present herein, or a subcombination of two or more such features, as well as any other features that may not necessarily be expressly described or inherently present in the present disclosure.

[0018] Broadly, embodiments of the inventive concepts disclosed herein relate to systems and methods for current measurement and ground fault detection using current measuring coils. Older ovens only use current measurement for each power phase. In newer ovens, it is also desirable to implement a ground fault detection system / circuitry system to detect current leakage. To this end, some ovens include a dedicated three-phase coil for ground fault detection. In this configuration, all three power phases are fed through three primary windings of the current measuring coil. The current through the secondary winding will be the sum of the three primary currents divided by the winding ratio. When the system is operating normally, the output is equal to zero. If there is an imbalance and the output is not equal to zero, then this indicates that there is a current leakage (also known as a ground fault). This method is effective, but in addition to the current measuring coil, another coil set or multi-phase coil assembly (e.g., a three-phase coil) for ground fault detection needs to be added. In order to implement the current measurement and ground fault detection functions with a reduced set of hardware, for equipment including a multi-phase power system, the embodiments described herein use a set of common coils to measure phase currents and detect ground faults.

[0019] In an embodiment, multiple (e.g., three) phase current measurement coils are placed in series so that the current / voltage across the phase current measurement coils is equal to the sum of their respective outputs. The sum of these outputs is then amplified to obtain a measurement of the sum of the detected phase currents. In order for this configuration to operate correctly, the conventional output of the phase current measurement circuit is to replace the rectifier in front of the resistor with a rectifier behind the sensing resistor, because once rectified, the voltage added together will not be zero under normal circumstances (no leakage current). In addition to working with fewer / smaller components, the current measurement and ground fault detection system / circuitry system with a rectifier behind the sensing resistor also has the advantage of having higher accuracy at current levels below 1A. The offset caused by the series placement of the phase current measurement coils must be removed so that the three currents can be read and processed separately. This is achieved by using three differential amplifiers, for example, by a differential amplifier in each phase current measurement circuit.

[0020] Some advantages of the disclosed current measurement and ground fault detection system / circuit system include the following. The current measurement and ground fault detection system / circuit system can achieve ground fault detection without the need for a separate large, bulky three-phase coil. Instead, the current measurement and ground fault detection system / circuit system utilizes existing phase current measurement coils and only adds a few small, lightweight and inexpensive components. The current measurement and ground fault detection system / circuit system also provides an improved implementation of the current measurement circuit with more linear characteristics.

[0021] Figure 11 is a block diagram illustrating a device 100 that may include a system / circuitry 200 for current measurement and ground fault detection according to an example embodiment of the present disclosure. In an embodiment, the device 100 is coupled to a power source 102 (e.g., a power supply unit (PSU), etc.), which is coupled to and / or is part of a multi-phase system 104 (e.g., a three-phase power system). The multi-phase system 104 may be configured to power one or more device components 106. For example, the device 100 may include an aircraft galley plug-in that includes components such as sensors, actuators, interface devices, controllers, heating / cooling elements, etc. In an example embodiment, the device 100 is an oven having one or more heating elements (components 106) powered by the multi-phase system 104.

[0022] The current measurement and ground fault detection system / circuitry 200 may be coupled to a portion of the multi-phase system 104. For example, in some embodiments, the current measurement and ground fault detection system / circuitry 200 may be coupled to a front end portion of the multi-phase system 104 (e.g., coupled to a connector or transmission line of the power source 102). In other embodiments, the current measurement and ground fault detection system / circuitry 200 may be coupled to an output portion of the multi-phase system 104 (e.g., coupled to a connector or transmission line of a component 106 powered by the multi-phase system 104). The current measurement and ground fault detection system / circuitry 200 may be coupled to any portion of the multi-phase system 104. For example, in some embodiments, the current measurement and ground fault detection system / circuitry 200 may be coupled to a middle portion of the multi-phase system 104 (e.g., coupled to a connector or transmission line between a front end portion and an output portion of the multi-phase system 104).

[0023] According to an exemplary embodiment of the present disclosure, Figure 2 1 . A current measurement and ground fault detection system / circuit system 200 is illustrated in FIG. 1 . In an embodiment, the current measurement and ground fault detection system / circuit system 200 includes a plurality of phase current measurement coils 202 (e.g., coils 202A, 202B, 202C) configured to detect phase currents associated with at least a portion of a multi-phase system 104. For example, the phase current measurement coils 202 may be configured to detect currents of respective phases of the multi-phase system 104 (e.g., currents flowing through respective connectors or transmission lines at the portion of the multi-phase system 104 to which the system / circuit system 200 is coupled). The current measurement and ground fault detection system / circuit system 200 also includes a plurality of phase current measurement circuits 300 (e.g., phase current measurement circuits 300A, 300B, and 300C) connected to the phase current measurement coils 202 and a ground fault detection circuit 400.

[0024] The phase current measurement circuit 300 is configured to measure the phase current detected by the phase current measurement coil 202. For example, each phase current measurement coil 202 may be coupled to a corresponding phase current measurement circuit 300 configured to measure the phase current detected by the phase current measurement coil 202. In an example embodiment, the phase current measurement circuits 300A, 300B, and 300C are coupled to and configured to measure the phase currents detected by the phase current measurement coils 202A, 202B, and 202C, respectively. Figure 2 As shown, each phase current measurement circuit 300 may be coupled to a first end and a second end of the secondary coil of a corresponding one of the phase current measurement coils 202 .

[0025] The ground fault detection circuit 400 is configured to measure the sum of the phase currents detected by the phase current measurement coils 202. For example, the ground fault detection circuit 400 may be configured to measure the sum of the three-phase currents detected by the phase current measurement coils 202A, 202B, and 202C. In an embodiment, the secondary sides (i.e., the secondary coils) of the phase current measurement coils 202 are connected in series with each other, and the ground fault detection circuit 400 is configured to measure the sum of the phase currents by detecting the current / voltage across the phase current measurement coils 202 connected in series. Figure 2 As shown, in an exemplary embodiment, a first end of the phase current measurement coil 202A is coupled to the ground fault detection circuit 400, a second end of the phase current measurement coil 202A is coupled to a first end of the phase current measurement coil 202B, a second end of the phase current measurement coil 202B is coupled to a first end of the phase current measurement coil 202C, and a second end of the phase current measurement coil 202C is coupled to the ground fault detection circuit 400. In this configuration, the ground fault detection circuit 400 can measure the sum of the current / voltage across the phase current measurement coils 202A, 202B, and 202C by detecting the current / voltage between the first end of the phase current measurement coil 202A and the second end of the phase current measurement coil 202C.

[0026] In an embodiment, the current measurement and ground fault detection system / circuitry 200 also includes a plurality of shunt resistors 204 (e.g., shunt resistors 204A, 204B, and 204C) coupled to respective phase current measurement coils 202. For example, each phase current measurement coil 202 may be connected in parallel with a respective shunt resistor 204. In an example embodiment, the phase current measurement coil 202A is connected in parallel with the shunt resistor 204A, the phase current measurement coil 202B is connected in parallel with the shunt resistor 204B, and the phase current measurement coil 202C is connected in parallel with the shunt resistor 204C. In this configuration, the voltage drop across each shunt resistor 204 is associated with the current detected by the phase current measurement coil 202 coupled to the shunt resistor 204. For example, the voltage drop across shunt resistor 204A is associated with the current detected by phase current measurement coil 202A, the voltage drop across shunt resistor 204B is associated with the current detected by phase current measurement coil 202B, and the voltage drop across shunt resistor 204C is associated with the current detected by phase current measurement coil 202C.

[0027] Reference now Figure 3, each phase current measurement circuit 300 is configured to measure the phase current detected by a corresponding one of the phase current measurement coils 202 by detecting a voltage drop across a corresponding one of the shunt resistors 204 (sometimes referred to as a "sense" resistor). In an embodiment, each phase current measurement circuit 300 includes a differential amplifier 302 configured to detect a voltage drop across a corresponding one of the shunt resistors 204. A positive result of this implementation is a more linear characteristic of the circuit (compared to the old approach) due to the improved linearity of the resistive load (Rshunt 204) seen by the current measurement coil 202 by replacing the rectifier diode with electronic rectification of an operational amplifier that produces a high impedance input and the location of the rectification is located after the sense resistor to reduce measurement errors in the current measurement and ground fault detection circuit system / system 200. In an embodiment, each phase current measurement circuit 300 also includes an active rectifier 304 (e.g., based on an operational amplifier) ​​and a low pass filter 306 in series with the differential amplifier 302. The signal from the differential amplifier 302 may be fed through an active rectifier 304 to obtain a DC signal, which is then filtered by a low pass filter 306 to an average voltage level to condition the signal for input to a controller 206 (e.g., a microcontroller, a microprocessor, etc.). In some embodiments, each phase current measurement circuit 300 also includes a buffer amplifier 308 configured to amplify the output (DC) signal from the low pass filter 306 before feeding the output signal to the controller 206. In general, the buffer amplifier 308 may be configured to condition (e.g., amplify or attenuate) the output signal based on the application (e.g., for input to a controller, or for input to another circuit or system).

[0028] As described above, the ground fault detection circuit 400 can measure the sum of the current / voltage across the phase current measurement coils 202A, 202B, and 202C connected in series by detecting the current / voltage between the first end of the phase current measurement coil 202A and the second end of the phase current measurement coil 202C. In an embodiment, the shunt resistors 204 are also connected in series with each other, and the ground fault detection circuit 400 is configured to measure the sum of the phase currents by detecting the voltage drop across the shunt resistors 204. Figure 4As shown, the ground fault detection circuit 400 may include a differential amplifier 402 configured to detect a voltage drop across the phase current measurement coils 202 and / or their corresponding shunt resistors 204. The amplification level (e.g., gain or power level) of the differential amplifier 402 of the ground fault detection circuit 400 may be higher than the amplification level of the differential amplifier 302 of the current measurement circuit 300. In an embodiment, the ground fault detection circuit 400 further includes an active rectifier 404 and a low pass filter 406 connected in series with the differential amplifier 402. The signal from the differential amplifier 402 may be fed through the active rectifier 404 to obtain a DC signal, which is then filtered by the low pass filter 406 to an average voltage level to condition the signal for input to the controller 206. In some embodiments, the ground fault detection circuit 400 further includes a buffer amplifier 408 configured to amplify the output signal (e.g., DC signal) from the low pass filter 406 before feeding the output signal to the controller 206. In general, buffer amplifier 408 may be configured to condition (eg, amplify or attenuate) the output signal based on the application (eg, for input to a controller, or for input to another circuit or system).

[0029] In some embodiments, the outputs of the phase current measurement circuit 300 and the ground fault detection circuit 400 are fed to the controller 206. The controller 206 can be configured to determine the phase current based on the output from the phase current measurement circuit 300. The controller 206 can also be configured to detect a ground fault based on the output of the ground fault detection circuit 400. For example, when the output of the ground fault detection circuit 400 is a non-zero output or indicates a non-zero sum of the currents detected by the phase current measurement coils 202, the controller 206 can detect a ground fault.

[0030] like Figure 2 As shown, in some embodiments, the controller 206 may include at least one processor 208, a memory 210, and a communication interface 212. The processor 208 provides processing functionality for at least the controller 206, and may include any number of processors, microcontrollers, circuit systems, field programmable gate arrays (FPGAs), or other processing systems, as well as resident or external memory for storing data, executable code, and other information accessed or generated by the controller 206. The processor 208 may execute one or more software programs implemented in a non-transitory computer-readable medium (e.g., memory 210) that implement the techniques described herein. The processor 208 is not limited by the materials from which it is formed or the processing mechanisms employed therein, and thus may be implemented via (one or more) semiconductors and / or transistors (e.g., using electronic integrated circuit (IC) components), etc.

[0031] The memory 210 may be an example of a tangible computer-readable storage medium that provides storage functionality to store various data and / or program codes related to the operation of the controller 206 / processor 208, such as software programs and / or code segments, or other data that instructs the processor 208 and possibly other components of the controller 206 to perform the functions described herein. Thus, the memory 210 may store data, such as a program of instructions for operating the controller 206 (including its components (e.g., the processor 208, the communication interface 212, etc.)). It should be noted that although a single memory 210 is described, multiple types and combinations of memories (e.g., tangible, non-transitory memories) may be employed. The memory 210 may be integrated with the processor 208, may include a separate memory, or may be a combination of both. Some examples of memory 210 may include removable and non-removable memory components, such as random access memory (RAM), read-only memory (ROM), flash memory (e.g., a secure digital (SD) memory card), a micro SD memory card and / or a micro SD memory card), a solid-state drive (SSD) memory, magnetic memory, optical memory, a universal serial bus (USB) storage device, hard disk memory, external memory, etc.

[0032] The communication interface 212 may be operably configured to communicate with components of the controller 206. For example, the communication interface 212 may be configured to retrieve data from the processor 208 or other devices (e.g., phase current measurement circuit 300, ground fault detection circuit 400, etc.), send data to be stored in the memory 210, retrieve data from a storage device in the memory 210, etc. The communication interface 212 may also be communicatively coupled with the processor 208 to facilitate data transfer between components of the controller 206 and the processor 208. It should be noted that while the communication interface 212 is described as a component of the controller 206, one or more components of the communication interface 212 may be implemented as external components that are communicatively coupled to the controller 206 via wired and / or wireless connections. The controller 206 may also include and / or be connected to one or more input / output (I / O) devices (e.g., human-machine interface (HMI) devices) via the communication interface 212. In an embodiment, the communication interface 212 may include a transmitter, a receiver, a transceiver, a physical connection interface, or any combination thereof.

[0033] Figure 5 An example implementation of a method 500 employing the current measurement and ground fault detection system / circuitry 200 described herein is illustrated. In general, the operations of a disclosed process (eg, method 500) may be performed in any order unless otherwise provided in the claims.

[0034] At step 502, the method 500 includes detecting phase currents with a plurality of phase current measurement coils 202. For example, the phase current measurement coils 202 may be configured to detect currents of respective phases of the multi-phase system 104 (e.g., currents flowing through respective connectors or transmission lines at a portion of the multi-phase system 104 to which the phase current measurement coils 202 are coupled).

[0035] At step 504, the method 500 includes measuring the phase currents detected by the phase current measurement coils 202 with the plurality of phase current measurement circuits 300. In some embodiments, the phase current measurement circuits 300 can output current measurement signals to the controller 206. The controller 206 can determine the phase current measurements based on the current measurement signals from the phase current measurement circuits 300.

[0036] At step 506, the method 500 includes measuring the sum of the phase currents detected by the phase current measurement coils 202 with the ground fault detection circuit 400. In an embodiment, a ground fault may be detected when the sum of the phase currents is a non-zero value (indicating the presence of a leakage current). For example, the ground fault detection circuit 400 may output a signal associated with a detected voltage drop or current across all phase current measurement coils 202 to the controller 206. When the output of the ground fault detection circuit 400 is a non-zero output or indicates a non-zero sum of the currents detected by the phase current measurement coils 202, the controller 206 may detect a ground fault.

[0037] The method 500 may also include any steps or operations implied or required by the embodiments of the current measurement and ground fault detection system / circuitry 200 described herein. The current measurement and ground fault detection system / circuitry 200 may also include any additional components or functions expressed or implied by the method 500.

[0038] It should be understood that the embodiments of the methods according to the inventive concepts disclosed herein may include one or more of the steps described herein. In addition, such steps may be performed in any desired order, and two or more steps may be performed simultaneously with each other. Two or more of the steps disclosed herein may be combined in a single step, and in some embodiments, one or more of the steps may be performed as two or more sub-steps. In addition, in addition to one or more of the steps disclosed herein, or as a substitute thereof, other steps or sub-steps may also be performed.

[0039] From the above description, it is apparent that the inventive concepts disclosed herein are well adapted to achieve the objects and advantages inherent in the inventive concepts mentioned herein and disclosed herein. Although the present preferred embodiments of the inventive concepts disclosed herein have been described for the purposes of this disclosure, it should be understood that many changes can be made, which are readily apparent to those skilled in the art and are accomplished within the broad scope and coverage of the inventive concepts disclosed and claimed herein.

Claims

1. A system for current measurement and ground fault detection, comprising: a plurality of phase current measurement coils configured to detect phase currents associated with at least a portion of a multi-phase system; a plurality of shunt resistors, wherein each of the phase current measurement coils is connected in parallel with a corresponding one of the shunt resistors; a plurality of phase current measurement circuits connected to the phase current measurement coils and configured to measure the phase currents detected by the phase current measurement coils, wherein each of the phase current measurement circuits is configured to measure the phase current detected by a corresponding one of the phase current measurement coils by detecting a voltage drop across a corresponding one of the shunt resistors, wherein each of the phase current measurement circuits comprises: a differential amplifier configured to detect a voltage drop across a corresponding one of the shunt resistors; and an active rectifier and a low pass filter in series with the differential amplifier; and a ground fault detection circuit connected to the phase current measuring coils and configured to measure a sum of phase currents detected by the phase current measuring coils, wherein the shunt resistors are connected in series with each other, and the ground fault detection circuit is configured to measure the sum of phase currents by detecting a voltage drop across the shunt resistors.

2. The system of claim 1, wherein the multiphase system is a three-phase system.

3. The system of claim 1, wherein each of the phase current measurement circuits further comprises a buffer amplifier configured to amplify the output signal from the low pass filter before feeding the output signal into a controller.

4. The system of claim 1, wherein the ground fault detection circuit comprises: a differential amplifier configured to detect a voltage drop across the shunt resistor; as well as An active rectifier and a low pass filter are connected in series with the differential amplifier.

5. The system of claim 4, wherein the ground fault detection circuit further comprises a buffer amplifier configured to amplify the output signal from the low pass filter before feeding the output signal into a controller.

6. An apparatus for ground fault detection using a current measuring coil, comprising: one or more components; a multi-phase system configured to provide power to the one or more components; a plurality of phase current measurement coils configured to detect phase currents associated with at least a portion of a multi-phase system; a plurality of shunt resistors, wherein each of the phase current measurement coils is connected in parallel with a corresponding one of the shunt resistors; a plurality of phase current measurement circuits connected to the phase current measurement coils and configured to measure the phase currents detected by the phase current measurement coils, wherein each of the phase current measurement circuits is configured to measure the phase current detected by a corresponding one of the phase current measurement coils by detecting a voltage drop across a corresponding one of the shunt resistors, wherein each of the phase current measurement circuits comprises: a differential amplifier configured to detect a voltage drop across a corresponding one of the shunt resistors; and an active rectifier and a low pass filter in series with the differential amplifier; and A ground fault detection circuit is connected to the phase current measuring coils and is configured to measure a sum of the phase currents detected by the phase current measuring coils.

7. The apparatus of claim 6, wherein the multiphase system is a three-phase system.

8. The apparatus of claim 6, wherein each of the phase current measurement circuits further comprises a buffer amplifier configured to amplify the output signal from the low pass filter before feeding the output signal to the controller.

9. The apparatus of claim 6, wherein the ground fault detection circuit comprises: a differential amplifier configured to detect a voltage drop across the shunt resistor; as well as An active rectifier and a low pass filter are connected in series with the differential amplifier.

10. The apparatus of claim 9, wherein the ground fault detection circuit further comprises a buffer amplifier configured to amplify the output signal from the low pass filter before feeding the output signal into a controller.

11. The apparatus of claim 6, wherein the apparatus is an oven and the one or more components include one or more heating elements.

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