A large current measurement device based on magnetic coupling mutual inductance voltage division structure

Abstract

The present invention discloses a large current measurement device based on a magnetic coupling mutual inductance voltage divider structure, comprising an incoming line shunt, a multi-coupled mutual inductance voltage divider coil, a magnetic energy detection unit, a magnetic energy storage unit and a control module. By setting a plurality of magnetic energy detection units, it is determined whether the current voltage signal exceeds a measurement threshold. If so, unactivated windings and corresponding magnetic energy detection units are continuously connected to ensure that the multi-coupled mutual inductance voltage divider coil does not reach the magnetic saturation in the nonlinear region, thereby achieving high-precision and wide-range current detection. Moreover, if the total voltage signal is still greater than the measurement threshold after all magnetic energy detection units are loaded, the electric energy in the energy storage element is discharged through the magnetic energy storage unit, thereby ensuring that the multi-coupled mutual inductance voltage divider coil does not reach the magnetic saturation in the nonlinear region.

Description

Technical Field

[0001] The present invention relates to the technical field of mutual inductors, and in particular to a large current measuring device based on a magnetic coupling mutual inductance voltage dividing structure. Background Art

[0002] In current high-current sensing applications, the excessive magnetic field strength around high-current conductors can easily lead to oversaturation of magnetic energy in highly sensitive or compact high-precision transformers, resulting in loss of linearity and significant current measurement errors. These transformers are also susceptible to interference from other magnetic sources or current fluctuations, causing circuit overshoot. While these effects can be mitigated by increasing the device size, thinning out the windings, reducing the material's magnetic sensitivity, and even increasing the measurement fit, the device's size, accuracy, and measurement range would not meet realistic installation and application requirements.

[0003] Numerous solutions exist for high-current detection. For example, Chinese Utility Model Application No. 200620026956.X proposes using an air-core coil current transformer to measure high currents. This reduces the device's size and mass, enhances insulation, internal winding core noise immunity, measurement bandwidth, and range, and eliminates the risk of terminal burnout and additional equivalent resistance. However, this structure lacks a magnetic core, making it difficult to accurately detect even small fluctuations in high currents. The output signal is easily affected by changes in the external magnetic field, and ambient temperature can affect the integration and filtering stages of the subsequent digital converter. Chinese Invention Application No. CN202111006599.6 proposes a magnetic modulation current detection method and measurement system using a four-core, six-coil, ultra-large-aperture structure. This system uses zero-flux feedback to suppress transformer effect interference, significantly reducing zero-point offset and improving measurement accuracy and stability. However, the multi-coil mutual inductance structure suffers from complex wiring and a large aperture. Adjustment methods based on feedback coil compensation involve numerous circuit components and a complex topology, thus failing to meet the requirements of compactness and easy installation. The mutual inductance current device mentioned in Chinese invention application CN202011564130.X has a high degree of integration with the digital signal source processing system, which can facilitate the collection of multi-line and large amounts of data. It has a relatively complete acquisition control logic and can accurately and reliably convert analog residual current into digital current signal extraction. However, the back-end processing module of the device is complex to implement and the mutual inductance component is too large, making it unsuitable for large current measurement.

[0004] In summary, existing magnetic current mutual inductance devices cannot simultaneously meet the requirements of high current detection for accuracy and measurement range. Summary of the Invention

[0005] In view of the above problems, the present invention proposes a large current measurement device based on a magnetic coupling mutual inductance voltage division structure, which mainly solves the problems of the background technology.

[0006] To solve the above technical problems, the first aspect of the present invention provides a large current measurement device based on a magnetic coupling mutual inductance voltage divider structure, comprising:

[0007] An incoming line shunt is used to receive input current from the primary bus, and a low-current branch in the incoming line shunt is coupled to the primary side of a multi-coupled mutual inductance voltage divider coil, the secondary side of the multi-coupled mutual inductance voltage divider coil includes multiple groups of parallel magnetically coupled windings, each of the windings includes an independent switching switch;

[0008] The winding is coupled with different magnetic energy detection units through the corresponding switching switches, or is coupled with the same magnetic energy storage unit, or its own closed loop is disconnected;

[0009] The magnetic energy detection unit is used to convert the induced current input by the corresponding winding into a voltage signal of a corresponding proportion. At the same time, at least one magnetic energy detection unit is coupled to one winding;

[0010] The magnetic energy storage unit is used to use the induced current as a current source to charge the energy storage element in the unit;

[0011] a control module, configured to receive the voltage signal and compare the voltage signal with a measurement threshold; if the voltage signal is greater than the measurement threshold, couple the remaining magnetic energy detection units to the winding one by one, accumulate all currently received voltage signals to generate a total voltage signal, and stop loading new magnetic energy detection units when the total voltage signal is less than the measurement threshold;

[0012] If the current total voltage signal is still greater than the measurement threshold after all the magnetic energy detection units are coupled with the corresponding windings, all the windings are coupled with the magnetic energy storage units, and the magnetic energy storage units discharge the electrical energy in the energy storage element.

[0013] In some embodiments, the incoming line diverter includes a potential terminal board and two shunt conductor plates, the surface of the potential terminal board is provided with a shunt plate socket, and the sides of the two shunt conductor plates are fixed with a guide thread knob column, and the guide thread knob column is inserted into the shunt plate socket.

[0014] In some embodiments, the multi-coupled mutual inductance voltage divider coil includes a circular magnetically sensitive core with an elliptical cross-section, a primary side of the circular magnetically sensitive core is coupled to the low current branch, and a secondary side of the circular magnetically sensitive core is coupled to the multiple groups of windings.

[0015] In some embodiments, the magnetic energy detection unit includes an induction current detection circuit and a protection circuit coupled to the induction current detection circuit.

[0016] In some embodiments, the induced current detection loop is a differential mode signal amplifier.

[0017] In some embodiments, the protection circuit is an AC transient suppression tube.

[0018] In some embodiments, the magnetic energy storage unit includes a rectifier stack, an LC filter, a DC converter, a low-bias linear regulator, and the energy storage element coupled in sequence.

[0019] A second aspect of the present invention provides a high current measurement method based on a magnetic coupling mutual inductance voltage divider structure, comprising the following steps:

[0020] receiving an input current from a primary bus, proportionally reducing the current value of the input current by a current shunting method, and proportionally reducing the voltage value of the input current by a voltage dividing method, and finally defining the result as an induced current;

[0021] In the initial stage, a magnetic energy detection unit converts the induced current into a voltage signal of a corresponding proportion. It is determined whether the voltage signal is greater than the measurement threshold. If so, the remaining magnetic energy detection units are loaded one by one. The induced current is measured in parallel by multiple magnetic energy detection units. All currently received voltage signals are accumulated to generate a total voltage signal. When the total voltage signal is less than the measurement threshold, the loading of new magnetic energy detection units is stopped.

[0022] If the current total voltage signal is still greater than the measurement threshold after all the magnetic energy detection units are loaded, the induced current is discharged.

[0023] The beneficial effects of the present invention are as follows: by setting up multiple magnetic energy detection units, it is determined whether the current voltage signal exceeds the measurement threshold. If so, the unactivated windings and corresponding magnetic energy detection units are continuously connected to ensure that the multi-coupled mutual inductance voltage divider coil does not reach the magnetic saturation in the nonlinear region, thereby achieving high-precision and wide-range current detection. Moreover, if the total voltage signal is still greater than the measurement threshold after all the magnetic energy detection units are loaded, the electric energy in the energy storage element is discharged through the magnetic energy storage unit to ensure that the multi-coupled mutual inductance voltage divider coil does not reach the magnetic saturation in the nonlinear region. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a system block diagram of a large current measurement device based on a magnetic coupling mutual inductance voltage division structure disclosed in the first embodiment of the present invention;

[0025] Figure 2 This is a structural diagram of the incoming line splitter disclosed in the first embodiment of the present invention;

[0026] Figure 3 This is a schematic structural diagram of a multi-coupled mutual inductance voltage divider coil disclosed in the first embodiment of the present invention;

[0027] Figure 4 This is a circuit schematic diagram of the magnetic energy detection unit disclosed in the first embodiment of the present invention;

[0028] Figure 5 This is a circuit diagram of the magnetic energy storage unit disclosed in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clearly understood, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the described embodiments are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0030] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected" and "fixed" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0031] Example 1

[0032] This embodiment provides a large current measurement device based on a magnetic coupling mutual inductance voltage division structure, such as Figure 1 As shown, it includes an incoming line shunt 1, a multi-coupled mutual inductance voltage divider coil 2, a magnetic energy detection unit 3, a magnetic energy storage unit 4 and a control module 5.

[0033] An incoming line shunt 1 is used to receive input current from the primary bus, and a low-current branch in the incoming line shunt 1 is coupled to the primary side of a multi-coupled mutual inductance voltage divider coil 2. The secondary side of the multi-coupled mutual inductance voltage divider coil 2 includes multiple sets of parallel magnetically coupled windings, each of which includes an independent switching switch;

[0034] The winding is coupled to different magnetic energy detection units 3 through corresponding switching switches, or coupled to the same magnetic energy storage unit 4, or disconnects its own closed loop;

[0035] The magnetic energy detection unit 3 is used to convert the induced current input by the corresponding winding into a voltage signal of corresponding proportion. At the same time, at least one magnetic energy detection unit 3 is coupled to one winding;

[0036] The magnetic energy storage unit 4 is used to use the induced current as a current source to charge the energy storage element in the unit;

[0037] The control module 5 is used to receive the voltage signal and compare the voltage signal with the measurement threshold. If the voltage signal is greater than the measurement threshold, the remaining magnetic energy detection units 3 are coupled to the winding one by one. All the currently received voltage signals are accumulated to generate a total voltage signal. When the total voltage signal is less than the measurement threshold, the loading of new magnetic energy detection units 3 is stopped.

[0038] If the current total voltage signal is still greater than the measurement threshold after all magnetic energy detection units 3 are coupled with the corresponding windings, all windings are coupled with the magnetic energy storage unit 4, and the magnetic energy storage unit 4 discharges the electrical energy in the energy storage element.

[0039] The overall effect of the device when it is running is as follows:

[0040] When a large busbar current flows into the device, it is split into two current loops by the incoming line current divider 1. The branch currents in both loops ultimately flow back to the busbar node. However, the loop with the smaller current flow is defined as the low-current branch (relative to the other branch) and serves as the primary winding of the multi-coupled mutual inductance voltage divider coil 2. The secondary side of the multi-coupled mutual inductance voltage divider coil 2 has multiple windings with magnetic mutual inductance coupling, each of which can obtain a certain amount of electrical energy from the primary side through the magnetic core via electromagnetic mutual inductance. The induced current generated by the secondary side is input into the magnetic energy detection unit 3 and forms a voltage signal that reflects the magnetic saturation of the multi-coupled mutual inductance voltage divider coil 2 and the magnitude of the primary current on the primary side. This voltage signal is read by the control module 5 and used to generate control information based on the internal algorithm. When the multi-coupled mutual inductance voltage divider coil 2 reaches the set pre-saturation threshold, the control module 5 activates and connects other windings coupled to the currently operating winding to share and absorb the magnetic energy induced by the primary side. The activated windings obtain multiple voltage information through each connected magnetic energy detection unit 3, which is separately input into the control module 5. The control module 5 will integrate these input information and calculate the corresponding bus maximum current value at that moment. The control module 5's strategy for connecting the coupled winding is: continuously connecting the unactivated coupled winding, always keeping the multi-coupled mutual inductance voltage divider coil 2 from reaching the magnetic saturation in the non-linear region, and at the same time maintaining the output voltage of each working winding at the maximum threshold of the winding without exceeding the limit. When the entire device exceeds the measurement threshold due to over-magnetic circuit saturation, the control module 5 will switch to the over-magnetic energy storage unit 4 for energy collection and storage, clear the overflow energy in the multi-coupled mutual inductance voltage divider coil 2, return to the zero magnetization energy storage state, and switch back to the detection mode to prepare for the next measurement. In addition, after the normal current value is collected, the control module 5 will also perform this switching operation once.

[0041] In summary, in this embodiment, by setting up multiple magnetic energy detection units 3, it is determined whether the current voltage signal exceeds the measurement threshold. If so, the unactivated windings and the corresponding magnetic energy detection units 3 are continuously connected to ensure that the multi-coupled mutual inductance voltage divider coil 2 does not reach the magnetic saturation in the nonlinear region, thereby achieving high-precision and wide-range current detection. Moreover, if the total voltage signal is still greater than the measurement threshold after all the magnetic energy detection units 3 are loaded, the electric energy in the energy storage element is discharged through the magnetic energy storage unit 4 to ensure that the multi-coupled mutual inductance voltage divider coil 2 does not reach the magnetic saturation in the nonlinear region.

[0042] Optionally, the structure of the incoming line splitter 1 of the present invention is as follows Figure 2 As shown. The incoming current diverter 1 includes a potential terminal plate 101 and two shunt conductor plates 102. The surface of the potential terminal plate 101 is provided with a shunt plate socket 103. The sides of the two shunt conductor plates 102 are fixed with a guide thread knob column 104, which is inserted into the shunt plate socket 103. The guide thread knob column 104, the potential terminal plate 101 and its connecting hardware are made of copper-nickel alloy, but are not limited to this material. The structure they form has both connecting and conducting functions, serving as both a fixture for the shunt conductor plates 102 and a current converging node. The shunt conductor plates 102 are composed of two copper-manganese alloy resistance strip plates, but are not limited to the aforementioned material. The two shunt conductor plates 102 are arranged vertically in a horizontal and vertical direction. When energized and diverted, they do not produce electrostatic breakdown and capacitance effects as would occur if they were placed in parallel. By changing the thickness of the two shunt conductor plates 102, the impedance of the plates can be changed, and the shunt ratio can be adjusted. During packaging, materials such as polytetrafluoroethylene (PTFE) can be used to seal and separate the two shunt conductor plates 102, facilitating electrical insulation. PTFE, with its excellent chemical stability and heat dissipation properties, is a suitable material for sealing the interior of the incoming shunt, but it is not the only material of choice. Copper-manganese alloy and copper-nickel alloy materials exhibit high temperature stability in their resistivity within a certain temperature range and offer excellent heat dissipation capabilities, making them preferred, but not exclusive, choices.

[0043] Optionally, the multi-coupled mutual inductance voltage divider coil 2 includes a circular magnetic sensitive core with an elliptical cross-section, the primary side of the circular magnetic sensitive core is coupled with the low current branch, and the secondary side of the circular magnetic sensitive core is coupled with multiple windings. Figure 3As shown, the secondary side of the multi-coupled mutual inductance voltage divider coil 2 of the present invention includes a plurality of windings having a magnetic mutual inductance coupling relationship, which are tentatively defined as secondary coupling winding A, secondary coupling winding B, secondary coupling winding C..., assuming that there are N such windings in total, and the number of windings N is determined according to actual needs. For example, the greater the measured bus current, the smaller the magnetic permeability or magnetic saturation of the magnetic core, the more turns of the secondary winding, etc., the more secondary windings N are required. The cross-section of the magnetic core of the multi-coupled mutual inductance voltage divider coil 2 is elliptical, and can be made of neodymium iron boron permanent magnet material as the magnetic core material, but is not limited to this material. The winding method of each winding is based on the mutual coupling relationship, and the tapped outgoing line is respectively connected to the switching switch component, which is responsible for switching the winding tapped outgoing line between the input end of the magnetic energy detection unit 3 and the magnetic energy storage unit 4, and the switching control is mainly completed by the control module 5. When secondary winding A is already in the magnetic circuit and secondary winding B is connected, the mutual induction magnetic field of winding B is established and evenly distributes the corresponding magnetic field energy. This, in turn, consumes the magnetic energy transmitted by the primary through multiple subsequent stages, ultimately achieving a state of magnetic equilibrium among the primary winding, winding A, and winding B, eliminating the existing magnetic saturation. Similarly, if the magnetic circuit formed by these three elements remains magnetically saturated after stabilization, winding C and further windings can be connected. Circular magnetically sensitive cores with elliptical cross-sections not only exhibit superior coercivity, maximum energy product, and permeability, but also possess excellent mechanical properties, enabling lightweight and thin designs.

[0044] Optionally, the magnetic energy detection unit 3 includes an induced current detection circuit and a protection circuit coupled to the induced current detection circuit. Figure 4 As shown, the secondary mutual inductance windings A, B, C, ..., all the way to winding N, can be equipped with corresponding secondary induced current detection circuits, protection circuits, and switching controls. First, the secondary winding current forms a protection circuit with N pairs of transient suppression diodes to prevent overvoltage and surges, preventing fluctuations in the primary mutual inductance from affecting subsequent modules. Second, the secondary windings can be connected to the subsequent current detection circuit or magnetic energy storage unit 4 through N switching components (i.e., S1, S2, S3, ..., N in total). This current detection is performed as shown in the figure, A:A, B:A, C:A, ..., N:A, a total of N. When the switch allows each secondary winding to connect to the current detection circuit, the secondary current is read and converted and amplified into a proportional voltage signal. Ultimately, it is read, stored, and analyzed through the analog-to-digital conversion channel of the control module 5 or an external ADC unit. Optionally, the induced current detection circuit is a differential mode signal amplifier. Optionally, the protection circuit is an AC transient suppression diode.

[0045] The magnetic energy storage unit 4 includes a rectifier stack, an LC filter, a DC converter, a low bias linear regulator and an energy storage element coupled in sequence. Figure 5As shown, it includes a magnetic energy cleaning circuit, a protection circuit, and a switching control for the N mutual inductance windings on the secondary side. First, the current of the secondary winding and N pairs of transient suppression tubes to prevent overvoltage and surge form a protection circuit to prevent the fluctuation of the primary mutual inductance from affecting the subsequent modules. Secondly, the secondary winding can be connected to the subsequent magnetic energy cleaning circuit or the magnetic energy detection unit 3 through N switching components, namely S1, S2, S3... a total of N. When the switching component allows each secondary winding to be connected to the magnetic energy cleaning circuit, the current induced in the secondary winding will be rectified, filtered, chopped, and regulated in sequence through the rectifier stack, LC filter, DC converter, and low-bias linear regulator, and finally stored in the energy storage element to prepare for the power supply of the entire system.

[0046] Example 2

[0047] This embodiment provides a high current measurement method based on a magnetic coupling mutual inductance voltage divider structure, including the following steps:

[0048] Step 1: Receive the input current of the primary bus, proportionally reduce the current value of the input current by a current shunting method, and proportionally reduce the voltage value of the input current by a voltage division method, and finally define it as the induced current;

[0049] Step 2: In the initial stage, a magnetic energy detection unit 3 converts the induced current into a voltage signal of corresponding proportion. It is determined whether the voltage signal is greater than the measurement threshold. If so, the remaining magnetic energy detection units 3 are loaded one by one. The induced current is measured in parallel by multiple magnetic energy detection units 3. All the currently received voltage signals are accumulated to generate a total voltage signal. When the total voltage signal is less than the measurement threshold, the loading of new magnetic energy detection units 3 is stopped.

[0050] Step 3: If the current total voltage signal is still greater than the measurement threshold after all the magnetic energy detection units 3 are loaded, the induced current is discharged.

[0051] In the description herein, it should be understood that terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0052] In this specification, reference to terms such as "one embodiment" or "example" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0053] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0054] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. A large current measurement device based on a magnetic coupling mutual inductance voltage divider structure, characterized in that: include: An incoming line shunt is used to receive input current from the primary bus, and a low-current branch in the incoming line shunt is coupled to the primary side of a multi-coupled mutual inductance voltage divider coil, the secondary side of the multi-coupled mutual inductance voltage divider coil includes multiple groups of parallel magnetically coupled windings, each of the windings includes an independent switching switch; The winding is coupled with different magnetic energy detection units through the corresponding switching switches, or is coupled with the same magnetic energy storage unit, or its own closed loop is disconnected; The magnetic energy detection unit is used to convert the induced current input by the corresponding winding into a voltage signal of a corresponding proportion. At the same time, at least one magnetic energy detection unit is coupled to one winding; The magnetic energy storage unit is used to use the induced current as a current source to charge the energy storage element in the unit; a control module, configured to receive the voltage signal and compare the voltage signal with a measurement threshold; if the voltage signal is greater than the measurement threshold, coupling the remaining magnetic energy detection units to the winding one by one, accumulating all currently received voltage signals to generate a total voltage signal; and stopping loading new magnetic energy detection units when the total voltage signal is less than the measurement threshold; If the current total voltage signal is still greater than the measurement threshold after all the magnetic energy detection units are coupled with the corresponding windings, all the windings are coupled with the magnetic energy storage units, and the magnetic energy storage units discharge the electrical energy in the energy storage element.

2. The large current measurement device based on the magnetic coupling mutual inductance voltage division structure according to claim 1, characterized in that: The incoming line diverter includes a potential terminal board and two shunt conductor plates. The surface of the potential terminal board is provided with a shunt plate socket. The sides of the two shunt conductor plates are fixed with a guide thread knob column, and the guide thread knob column is inserted into the shunt plate socket.

3. The large current measurement device based on the magnetic coupling mutual inductance voltage division structure according to claim 1, characterized in that: The multi-coupled mutual inductance voltage divider coil includes a circular magnetically sensitive core with an elliptical cross-section. The primary side of the circular magnetically sensitive core is coupled to the low current branch, and the secondary side of the circular magnetically sensitive core is coupled to the multiple groups of windings.

4. The large current measurement device based on the magnetic coupling mutual inductance voltage division structure according to claim 1, characterized in that: The magnetic energy detection unit includes an induction current detection circuit and a protection circuit coupled to the induction current detection circuit.

5. The large current measuring device based on the magnetic coupling mutual inductance voltage dividing structure according to claim 4, characterized in that: The induced current detection loop is a differential mode signal amplifier.

6. The large current measuring device based on the magnetic coupling mutual inductance voltage dividing structure according to claim 4, characterized in that: The protection circuit is an AC transient suppression tube.

7. The large current measuring device based on the magnetic coupling mutual inductance voltage division structure according to claim 1, characterized in that: The magnetic energy storage unit includes a rectifier stack, an LC filter, a DC converter, a low-bias linear regulator and the energy storage element coupled in sequence.

8. A method for measuring a large current based on a magnetic coupling mutual inductance voltage divider structure, used in the large current measuring device based on a magnetic coupling mutual inductance voltage divider structure according to any one of claims 1 to 7, characterized in that: The following steps are involved: receiving an input current from a primary bus, proportionally reducing the current value of the input current by a current shunting method, and proportionally reducing the voltage value of the input current by a voltage dividing method, and finally defining the result as an induced current; In the initial stage, a magnetic energy detection unit converts the induced current into a voltage signal of a corresponding proportion. It is determined whether the voltage signal is greater than the measurement threshold. If so, the remaining magnetic energy detection units are loaded one by one. The induced current is measured in parallel by multiple magnetic energy detection units. All currently received voltage signals are accumulated to generate a total voltage signal. When the total voltage signal is less than the measurement threshold, the loading of new magnetic energy detection units is stopped. If the current total voltage signal is still greater than the measurement threshold after all the magnetic energy detection units are loaded, the induced current is discharged.

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