CN111198292A - Current sensing device and method - Google Patents
Current sensing device and method Download PDFInfo
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- CN111198292A CN111198292A CN201811366173.XA CN201811366173A CN111198292A CN 111198292 A CN111198292 A CN 111198292A CN 201811366173 A CN201811366173 A CN 201811366173A CN 111198292 A CN111198292 A CN 111198292A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/02—Measuring effective values, i.e. root-mean-square values
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R13/00—Details of coupling devices of the kinds covered by groups H01R12/70 or H01R24/00 - H01R33/00
- H01R13/66—Structural association with built-in electrical component
- H01R13/665—Structural association with built-in electrical component with built-in electronic circuit
- H01R13/6683—Structural association with built-in electrical component with built-in electronic circuit with built-in sensor
Abstract
When the existing non-contact current measuring device utilizes the magnetic sensor to sense the induced magnetic field derived from the cable, the environmental magnetic field component carried by the sensed magnetic field signal is not filtered, so that the accuracy of the current value calculated by the rear-end processor is not high or the current value varies greatly. In view of the above, the present invention provides a current sensing apparatus and method, wherein the current sensing apparatus comprises: the magnetic sensor comprises at least one magnetic sensor, a signal receiving unit and a processor. In particular, the invention utilizes a mode of planning an environmental magnetic field filtering unit and an effective current operation unit in the processor; the environment magnetic field filtering unit is used for filtering an environment magnetic field component carried by a magnetic field sensing signal, so that the effective current computing unit can compute a current value transmitted by a cable according to a first magnetic field sensing signal, and the sensing accuracy of the current sensing device on the current carried by the cable is improved by the method.
Description
Technical Field
The present invention relates to the field of current sensing technologies, and more particularly, to a current sensing apparatus and method.
Background
In recent years, taiwan pays more attention to the problems of global warming and energy shortage, so that people are often encouraged to save energy and electricity through the implementation of reward measures. For example, taiwan power companies often launch power saving reward activities in summer. In order to enable people to detect the electricity consumption condition of household electrical appliances, for example, a power supply sensor of an intelligent electric meter is provided in the market, and the functions of detecting the voltage, the current, the electricity consumption, the power and the electricity consumption of the electrical appliances are provided.
The non-contact power sensing device called "electric meter sticky note" is introduced by the institute of industrial technology, and the technology thereof is disclosed in U.S. patent publication No. US2017/0023625a 1. Fig. 1 is a perspective view of a non-contact three-phase three-wire power line measuring device disclosed in U.S. patent publication No. US2017/0023625a 1. As shown in fig. 1, the non-contact three-phase three-wire power line measuring device 1' mainly includes: a housing 10 ', a plurality of current sensors 11', a plurality of voltage sensors 12 ', and an electronic module 13'; the housing 10 ' is used for covering the three cables 2 ', and the plurality of current sensors 11 ' and the plurality of voltage sensors 12 ' are disposed on the outer surface of the housing 10 '. In particular, the current sensor 11' is a magnetic sensor; on the other hand, the voltage sensor 12' is known as a metal electrode by referring to U.S. Pat. No. US9,007,077B2.
Briefly, the non-contact power sensing device introduced by the institute of industrial technology has a variety of functions, including: non-contact current measurement, non-contact voltage measurement, and power consumption calculation and display. However, based on the fact that the non-contact current measurement is performed by using one or more magnetic sensors (current sensors 11 '), the inventors found in the practical research process that such non-contact current measurement technique may cause significant errors in current measurement due to the different thickness of the cable or the different installation positions of the housing 10'. Please refer to fig. 2, which shows the magnetic force line distribution of two current transmission lines. According to the ampere (right-hand) law, if a long straight wire carrying current I vertically penetrates out of a paper surface, a circle with radius r can be drawn by taking the wire as the center of the circle, wherein the magnetic field of each point on the circumference of the circle is equal in magnitude and can be calculated by the following formula:
therefore, when a multifunctional power sensor (i.e., a non-contact three-phase three-wire power line measuring device disclosed in U.S. patent publication No. US2017/0023625a 1) introduced by the research institute of industrial technology performs two current detections on one current-carrying cable 2 ', if the distance between the current sensor 11 ' for the first current detection and the cable 2 ' is different from the distance between the current sensor 11 ' for the second current detection and the cable 2 ', the current values measured by the two current detections are significantly different. The reason is that: the magnitude of the magnetic field derived from the current carried by a long straight wire is inversely proportional to the radius r. On the other hand, when the current detection is performed, the conventional multifunctional power sensor does not filter out the dc component in the current signal, so that the accuracy of the measured current value varies too much, which cannot be compared with the conventional electric meter.
Engineers familiar with electromagnetic theory and non-contact current sensing technology can learn from the above description that the existing non-contact current sensing device shows high measurement inaccuracy and instability in practical application; accordingly, the present invention is directed to a current sensing apparatus and method thereof.
Disclosure of Invention
The current measuring device of the prior art does not filter out the dc component of the current signal when performing the current detection, which results in a large variation of the accuracy of the current value. Meanwhile, the existing non-contact current measuring device can generate obvious errors in current measurement due to different thicknesses of cables to be measured or different installation positions of the measuring device. It is therefore a primary objective of the claimed invention to provide a current sensing apparatus and method to improve or solve the above-mentioned shortcomings of the prior art.
To achieve the above objective of the present invention, the present inventors provide an embodiment of the current sensing apparatus, which includes:
at least one magnetic sensor located at an initial sensing position and spaced from a cable by a sensing distance; the magnetic sensor senses a first sensing magnetic field of the cable at the initial sensing position and outputs a first magnetic field sensing signal;
a signal receiving unit electrically connected to the magnetic sensor for receiving the first magnetic field sensing signal; and
a processor electrically connected to the signal receiving unit and having an ambient magnetic field filtering unit and an effective current computing unit;
the environment magnetic field filtering unit is used for filtering an environment magnetic field component carried by the first magnetic field sensing signal, so that the effective current computing unit can compute a current value transmitted by the cable according to the first magnetic field sensing signal.
To achieve the above objective of the present invention, the present inventors also provide an embodiment of the current sensing method, which includes the following steps:
(1) providing a current sensing device comprising at least one magnetic sensor, a signal receiving unit and a processor; wherein, the processor is provided with an environmental magnetic field filtering unit and an effective current operation unit;
(2) enabling the magnetic sensor to sense a first sensing magnetic field of the cable on an initial sensing position and outputting a first magnetic field sensing signal;
(3) the processor receives the first magnetic field sensing signal output by the magnetic sensor through the signal receiving unit;
(4) the ambient magnetic field filtering unit filters an ambient magnetic field component carried by the first magnetic field;
(5) the effective current computing unit computes a current value transmitted by the cable according to the first magnetic field sensing signal.
Drawings
FIG. 1 is a perspective view showing a non-contact three-phase three-wire power cord measuring device disclosed in U.S. patent publication No. US2017/0023625A 1;
FIG. 2 is a diagram showing the distribution of magnetic lines of force of two current transmission lines;
FIG. 3 is a perspective view showing a first embodiment of the current sensing device of the present invention;
FIG. 4 is a diagram showing the structure of a first embodiment of the current sensing device of the present invention;
FIG. 5 is an exploded view showing a portion of a power plug having a current sensing device of the present invention;
FIG. 6 is a top view showing the base of the power plug and the magnetic sensor;
FIG. 7 is a top view showing the power plug and wires;
FIG. 8 is a graph of data showing measured current versus sensed current;
FIG. 9 is a graph of data showing measured current versus sensed current;
FIG. 10 is a graph of data showing the stability of the sensed current;
FIG. 11 is a diagram showing the structure of a second embodiment of the current sensing device of the present invention;
FIG. 12 is a side cross-sectional view showing the cable and magnetic sensor;
FIG. 13 is a top view showing the base of the power plug, the magnetic sensor, and the sensing position adjusting unit;
fig. 14 is a perspective view showing a power plug;
fig. 15 is a perspective view showing a magnetic ring and a magnetic sensor;
FIG. 16A is a flow chart illustrating a current sensing method of the present invention;
FIG. 16B is a flow chart showing a current sensing method of the present invention; FIG. 16C is a flow chart showing a current sensing method of the present invention.
Wherein the reference numerals are:
31 base
32 Top cover
33 electric connection terminal
2 cable conductor
1 Current sensing device
11 magnetic sensor
12 signal receiving unit
13 processor
14 signal transmission unit
10 circuit board
16 power supply unit
131 ambient magnetic field filtering unit
132 effective current operation unit
134 microprocessor unit
4 electronic device
17 sensing position adjusting unit
133 sense current correction unit
18 magnetic ring
181 gap
171 track group
172 carrying element
173 control member
S1-S5 steps
Step S6
S6a-S8a steps
21 conducting wire
22 insulating sheath
Pin initial sensing position
P1 first adjustment sensing position
1' non-contact three-phase three-wire power line measuring device
10' shell
11' current sensor
12' voltage sensor
13' electronic module
2' cable conductor
Detailed Description
In order to more clearly describe the current sensing apparatus and method of the present invention, a preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
First embodiment
The current sensing device of the present invention can be applied to any conventional power supply device, such as: a contactless Power sensor, an electric meter (Power meter), a Power outlet (Power outlet), a Power plug (Power plug), a Power converter, a Power adapter (Power adapter), or a Power extension cord. Fig. 3 and 4 are a perspective view and an architecture diagram illustrating a first embodiment of the current sensing device of the present invention, and fig. 5 is a partial exploded view illustrating a power plug having the current sensing device of the present invention. As can be seen from fig. 5, the power plug 3 mainly includes: a base 31, a top cover 32, two electrical connection terminals 33, and two electrical cables 2. On the other hand, as shown in fig. 3 and 4, the current sensing apparatus 1 of the present invention mainly includes: at least one magnetic sensor 11, a signal receiving unit 12, a processor 13, and a signal transmitting unit 14.
In order to make the current sensing device 1 of the present invention easily integrated into the power plug 3, the signal receiving unit 12, the processor 13 and the signal transmitting unit 14 can be disposed on a circuit board 10, and then the circuit board 10 is fixed in the base 31 of the power plug 3. According to the design of the present invention, the magnetic sensor 11 is located at an initial sensing position in the base 31 and is separated from one of the two cables 2 by a sensing distance. Usually, the two cables 2 are live wire (Livewire) and Neutral wire (Neutral wire), and the magnetic sensor 11 is disposed near the live wire (L). It should be noted that a power supply unit 16 is further disposed on the circuit board 10 for supplying power required by the signal receiving unit 12, the processor 13 and the signal transmitting unit 14. Of course, the power supply unit 16 is not limited to a power supply or a power converter, and may be a battery or a voltage regulator (voltage regulator).
Thus, the processor 13 can control the magnetic sensor 11 to sense a first induced magnetic field of the cable 2 at the initial sensing position and output a first magnetic field sensing signal. Further, the processor 13 receives the first magnetic field sensing signal through the signal receiving unit 12, and filters an ambient magnetic field component carried by the first magnetic field sensing signal by an ambient magnetic field filtering unit 131 inside the processor. Then, an effective current computing unit 132 inside the processor 13 can compute a value of a current transmitted by the cable 2 based on the first magnetic field sensing signal. Finally, a microprocessor unit 134 within the processor 13 can transmit the calculated value of the current to an external electronic device 4 through the signal transmission unit 14, such as: the smart phone, the smart watch, the smart glasses, the tablet computer, the notebook computer, or other electronic devices having wireless transmission interfaces or wired transmission interfaces.
It should be appreciated by electronic engineers who have good current sensing technology using magnetic sensing elements that the magnetic sensor 11 senses the magnetic field derived from the current carried by the cable 2 based on the control of the processor 13 so that the processor 13 can utilize the magnetic field
The value of the sense current is calculated. However, the magnetic field signal sensed by the magnetic sensor 11 may include both the Induced magnetic field (Induced magnetic field) of the cable 2 and the ambient magnetic field, if directly used by the processor 13
The formula (a) converts the first magnetic field sensing signal into a current signal, and the resulting current value may be very different from the actual value. For this reason, the present invention particularly programs the ambient magnetic field filtering unit 131 and the effective current computing unit 132 inside the processor 13; the environmental magnetic field filtering unit 131 utilizes an environmental magnetic field filtering expression to filter the environmental magnetic field, and the effective current computing unit 132 utilizes an effective current expression to compute the value of the current transmitted by the cable 2. The ambient magnetic field filtering expression and the effective current expression are respectively expressed by the following expressions (1) and (2), and the definition of the algebraic or variable in the two expressions is summarized in the following table (1).
Watch (1)
Correction mode of sensing current
Fig. 6 is a top view showing a base and a magnetic sensor of the power plug, and fig. 7 is a top view showing the power plug and a wire. As shown in fig. 6, the magnetic sensor 11 is placed on the base 31 of the power plug 3 so as to be directly adjacent to the lead wire 21 of the electric cable 2. On the other hand, as shown in fig. 7, the magnetic sensor 11 is removed from the power plug 3 and placed at a position close to the insulating sheath 22 of the electric cable 2. After the magnetic sensor 11 measures the magnetic field signal of the conducting wire 21 at two positions, the ambient magnetic field filtering unit 131 of the processor 13 filters the ambient magnetic field component contained in the magnetic field signal, so that the effective current computing unit 132 then computes a value of the current transmitted by the cable 2. Then, the effective current operation unit 132 and the sensed current correction unit 133 in the processor 13 can calculate the so-called current correction parameter by using the following mathematical expressions (I ') and (II'), and complete the current correction; wherein the definitions of the algebra or variables in the mathematical expressions (I ') and (II') are collated in the following table (2).
ICal＝(IRMS)/k,k＝Imea/I1..............................(II')
Watch (2)
Both fig. 8 and 9 show graphs of measured current versus sensed current. It is to be noted that the data of the measured current is measured by a standard measuring device (e.g., a current measuring device)) Measured from the electric cable 2. On the other hand, the sensed current data of fig. 8 is measured by placing the magnetic sensor 11 inside the power plug 3 (refer to fig. 6), and the sensed current data of fig. 9 is measured by placing the magnetic sensor 11 near the insulating sheath 22 of the electric cable line 2 (refer to fig. 7). From the data of fig. 8, it can be found that the R-square value of the trend line of the sensed current measured by placing the magnetic sensor 11 within the power plug 3 is closer to 1 than the sensed current measured by placing the magnetic sensor 11 close to the insulating sheath 22 of the electric cable 2. Please refer to fig. 2 repeatedly showing the magnetic force line distribution of the two current transmission lines. According to the ampere (right-hand) law, if a long straight wire carrying current I vertically penetrates out of a paper surface, a circle with radius r can be drawn by taking the wire as the center of the circle, wherein the magnetic field of each point on the circumference of the circle is equal in magnitude and can be calculated by the following formula:
based on the theory of magnetic field equipotential lines, the magnetic field strength measured with the magnetic sensor 11 placed inside the power plug 3 must be higher than the magnetic field strength measured with the magnetic sensor 11 placed close to the insulating sheath 22 of the cable wires 2. This is why the R-squared value of the trend line of the sensed current measured by placing the magnetic sensor 11 inside the power plug 3 is relatively close to 1.
However, after the completion of the calibration procedure, as shown in fig. 9, the R-squared values of both the trend line of the sensed current measured by placing the magnetic sensor 11 close to the insulating sheath 22 of the electric cable wire 2 and the trend line of the sensed current measured by placing the magnetic sensor 11 inside the power plug 3 are close to 1. In short, the square value of R reflects the relationship of multiple linear regression, and the closer to 1, the higher the reliability of the obtained data. Continuing to refer to FIG. 10, a data plot illustrating the stability of the sensed current is shown. In order to determine that the calibration manner of the sensed current does help to improve the measurement accuracy of the current sensing apparatus 1 of the present invention, the present inventors used the data of the current carried by the electric meter directly from the conductor 21 of the electric cable 2 as the basis for calculating the measurement accuracy of the current sensing apparatus 1 of the present invention. As can be seen from fig. 10, the measurement accuracy of the current sensing apparatus 1 of the present invention can be controlled within ± 0.5%.
Second embodiment
As can be seen from the above description, the present invention utilizes a manner of planning an ambient magnetic field filtering unit 131 and an effective current computing unit 132 inside the processor 13, so that the processor 13 can calculate the correct value of the sensing current under the condition of filtering the ambient magnetic field component carried by the sensing magnetic field signal; meanwhile, the current measurement of the cable 2 is performed by using a standard measurement device in cooperation with the use of the sensing current calibration unit 133, so as to complete the calibration of the current of the cable 2 measured by the current sensing device 1, thereby greatly improving the sensing accuracy of the current sensing device 1. Further, the present invention also proposes a second embodiment of the current sensing device 1.
FIG. 11 is a diagram showing a second embodiment of the current sensing device of the present invention. As can be seen from comparing fig. 11 and fig. 4, the second embodiment of the current sensing apparatus 1 further includes a set of sensing position adjusting units 17; the sensing position adjusting unit 17 is configured to displace the magnetic sensor 11 to adjust the initial sensing position to a first adjusted sensing position, so that the magnetic sensor 11 can sense a second induced magnetic field derived from the current transmitted by the cable 2 at the first adjusted sensing position.
Another way of correcting the sensed current
Fig. 12 is a side sectional view showing the cable and the magnetic sensor. As shown in fig. 12, it is assumed that the magnetic sensor 11 is at the initial sensing position PinAbove the first adjustment sensing position P, is at a distance r from the wire 21 inside the cable 21At a distance r + d from the conductor 21 inside the cable wire 2. Thus, the sensing current calibration unit 133 can use the following mathematical expressions (I), (II) and (III) to complete the calibration of the sensing current; wherein the definitions of the algebra or variables in the mathematical expressions (I), (II) and (III) are summarized in the following table (3).
Watch (3)
Since the value of r includes the thickness of the insulating sheath 22 of the cable 2 and the distance between the magnetic sensor 11 and the insulating sheath 22, the thickness of the insulating sheath 22 can be preset according to empirical values, thereby determining the value of r. Continuously, based on the magnetic field data measured by the magnetic sensor 11 in the first sensing operation, the value of the current carried by the cable 2 can be calculated by using the mathematical expression (I). Further, r' (i.e., the correction value of r) can be calculated by substituting the current value calculated by the mathematical expression (I) and the magnetic field data measured by the magnetic sensor 11 at the first adjustment sensing position P1 into the mathematical expression (II). Having obtained the value of r', Ical (i.e., the corrected current value) can then be calculated using mathematical expression (III). In short, it is assumed that the current value measured by the magnetic sensor 11 above the initial sensing position Pin is correct; then, after the magnetic sensor 11 is moved by a distance d, the sensing of the second induced magnetic field is completed. Based on the Biot-Savart law, the value of the current measured by the magnetic sensor 11 above the initial sensing position Pin should be equal to the value of the current measured by the magnetic sensor 11 at the first adjusted sensing position P1. Therefore, as shown in the above mathematical expression (II), it can be assumed that the current measured by the magnetic sensor 11 at the first adjusted sensing position P1 is equal to the current measured by the magnetic sensor 11 at the initial sensing position Pin, and then the magnetic field data measured by the magnetic sensor 11 at the first adjusted sensing position P1 and the moving distance d are substituted into the mathematical expression (II), so as to obtain the corrected distance (i.e. r').
In this way, even if the distance r varies with the thickness of the insulating sheath 22 of different cable wires 2, if r is corrected by the first correction method for sensing current proposed by the present invention, the correct sensing current value can be calculated by using the bio-Savart law (Biot-Savart law), thereby improving the sensing accuracy of the current sensing device 1 of the present invention for the current transmitted by the cable wire 2.
Please refer to fig. 13, which is a top view of the base, the magnetic sensor, and the sensing position adjusting unit of the power plug. Fig. 14 is a perspective view of the power plug. As can be understood from fig. 11, 13 and 14, the exemplary embodiment of the sensing position adjusting unit 17 includes: the track device comprises a track set 171, a carrier 172 movable on the track set 171, and a control member 173 for driving the carrier 172 to move. The track set 171 may be a track set with a sliding slot or a track set with a tooth slot. In the calibration of the sensing current, the current sensing apparatus 1 can integrate the data of the first sensing operation and the second sensing operation by only moving the carrier 172 with the magnetic sensor 11 on the track set 171 for a distance through the control part 173. It must be emphasized that the current sensing device 1 applying the present invention does not limit that the magnetic sensor 11 must be located inside the power plug 3 when detecting the current of any of the electric cables 2. Therefore, the sensing position adjusting unit 17 may be provided outside the power plug 3 in synchronization with the installation position of the magnetic sensor 11.
Please refer to fig. 3 again, and also refer to a perspective view of the magnetic ring and the magnetic sensor shown in fig. 15. When implementing the current sensing device 1 of the present invention, a magnetic ring 18 is sleeved on the cable 2, and the magnetic sensor 11 is disposed in a notch 181 of the magnetic ring 18. With such an arrangement, the magnetic ring 18 can be used to guide the magnetic field derived from the current transmitted by the cable 2, so that the magnetic field passes through the notch 181, thereby improving the magnetic field sensing accuracy of the magnetic sensor 11. Meanwhile, an electromagnetic shielding layer may further be disposed on the magnetic ring 18 to shield the external magnetic field, so as to prevent the external magnetic field from interfering with the magnetic field derived from the current transmitted by the cable 2. It has to be specified that, in general, the magnetic sensor 11 is used to perform magnetic field sensing on the live line of the two electric cables 2; thus, when using magnetic ring 18, it is necessary to pass the live wire through magnetic ring 18 and to limit the neutral wire from being located outside magnetic ring 18.
Thus, the above description has been presented for the purpose of illustrating the various embodiments of the current sensing apparatus 1 of the present invention; next, a current sensing method of the present invention will be described continuously. 16A, 16B and 16C are flow charts illustrating the current sensing method of the present invention; in which, fig. 16A includes five steps for performing current detection on the cable 2 (as shown in fig. 3); the five steps include the following steps:
step S1: providing a current sensing device 1 comprising at least one magnetic sensor 11, a signal receiving unit 12 and a processor 13; wherein, the processor 13 has an ambient magnetic field filtering unit 131 and an effective current computing unit 132;
step S2: enabling the magnetic sensor 11 to sense a first induced magnetic field of the cable 2 at an initial sensing position Pin and output a first magnetic field sensing signal;
step S3: the processor 13 receives the first magnetic field sensing signal output by the magnetic sensor 11 through the signal receiving unit 12;
step S4: the ambient magnetic field filtering unit 131 filters an ambient magnetic field component carried by the first magnetic field; and
step S5: the effective current computing unit 132 computes a current value transmitted by the cable 2 according to the first magnetic field sensing signal.
It should be noted that if the current sensing method is compiled as application software in the form of a library, variables or operands and is built into the first embodiment of the current sensing apparatus 1 of the present invention (as shown in fig. 3), fig. 16B includes a step for calibrating the current measured by the cable 2; the execution content of the step is as follows:
step S6: the sensing current correction unit 133 can correct the value of the current calculated by the effective current operation unit 132 based on the value of the current calculated by the effective current operation unit 132 and the value of a measured current measured by a current measuring device from the cable 2.
In the step S4 and the step S5, the ambient magnetic field filtering unit 131 utilizes an ambient magnetic field filtering expression to filter ambient magnetic field components, and the effective current computing unit 132 utilizes an effective current expression to compute the value of the current transmitted by the cable 2. The ambient magnetic field rejection expression and the effective current expression are expressed by the above-described expressions (1) and (2). In step S6, the effective current calculating unit 132 and the sensed current correcting unit 133 calculate a so-called current correction parameter by using the above-mentioned mathematical expressions (I ') and (II'), and complete the current correction.
On the other hand, if the current sensing method is compiled as application software in the form of a library, variables or operands and is built into the second embodiment of the current sensing apparatus 1 of the present invention (as shown in fig. 11), fig. 16C includes three steps for calibrating the current measured by the cable 2; the execution content of the step is as follows:
step S6 a: displacing the magnetic sensor 11 to make the magnetic sensor 11 located above a first adjusted sensing position P1;
step S7 a: allowing the magnetic sensor 11 to sense a second induced magnetic field of the cable 2 at the first adjusted sensing position P1 and output a second magnetic field sensing signal, and then repeating the steps S3 to S5; and
step S8 a: based on the first magnetic field sensing signal and the second magnetic field sensing signal, the sensing current calibration unit 133 calibrates the value of the current transmitted by the cable 2 calculated by the effective current calculation unit 132.
In step S8a, the effective current computing unit 132 and the sensed current correcting unit 133 calculate a so-called r correction value by using the above-mentioned mathematical expressions (I), (II) and (III), and complete the current correction.
Thus, the above-mentioned current sensing apparatus and method of the present invention are fully and clearly illustrated, and thus the following advantages can be obtained:
(1) when the existing non-contact current measuring device utilizes the magnetic sensor to sense the induced magnetic field derived from the cable, the environmental magnetic field component carried by the sensed magnetic field signal is not filtered, so that the accuracy of the current value calculated by the rear-end processor is not high or the current value varies greatly. In view of the above, the present invention provides a current sensing apparatus 1, comprising: at least one magnetic sensor 11, a signal receiving unit 12 and a processor 13. In particular, the present invention utilizes a method of programming an ambient magnetic field filtering unit 131 and an effective current computing unit 132 inside the processor 13; the environmental magnetic field filtering unit 131 is configured to filter an environmental magnetic field component carried by the magnetic field sensing signal, so that the effective current calculating unit 132 can calculate a current value transmitted by the cable 2 according to the magnetic field sensing signal, thereby improving the sensing accuracy of the current sensing device 1 for the current carried by the cable 2.
(2) On the other hand, the conventional non-contact current measuring device has obvious errors in current measurement due to different thicknesses of cables to be measured or different installation positions of the measuring device. In order to improve the drawbacks of the prior art, the present invention adds a sensing current calibration unit 133 to the processor 13; thus, based on the value of the current calculated by the effective current operation unit 132 and the value of a measured current measured by a current measuring device from the cable 2, the sensed current correction unit 133 can correct the value of the current calculated by the effective current operation unit 132.
It should be emphasized that the above detailed description is specific to possible embodiments of the invention, but this is not to be taken as limiting the scope of the invention, and all equivalent implementations or modifications that do not depart from the technical spirit of the invention are intended to be included within the scope of the present invention.
Claims (20)
1. A current sensing device, comprising:
at least one magnetic sensor located at an initial sensing position and spaced from a cable by a sensing distance; the magnetic sensor senses a first sensing magnetic field of the cable at the initial sensing position and outputs a first magnetic field sensing signal;
a signal receiving unit electrically connected to the magnetic sensor for receiving the first magnetic field sensing signal; and
a processor electrically connected to the signal receiving unit and having an ambient magnetic field filtering unit and an effective current computing unit;
the environment magnetic field filtering unit is used for filtering an environment magnetic field component carried by the first magnetic field sensing signal, so that the effective current computing unit can compute a current value transmitted by the cable according to the first magnetic field sensing signal.
2. The current sensing device of claim 1, further comprising:
a sensing position adjusting unit for displacing the magnetic sensor to adjust the initial sensing position to a first adjusted sensing position;
the magnetic sensor senses a second induced magnetic field of the cable at the first adjustment sensing position and outputs a second magnetic field sensing signal.
3. The current sensing device of claim 1, further comprising:
a magnetic ring, which is sleeved on the cable and is provided with a notch for the magnetic sensor to be arranged in; the magnetic ring is used for guiding a magnetic field derived from current transmitted by the cable so that the magnetic field passes through the notch.
4. The current sensing device of claim 1, further comprising:
a power supply unit for supplying the power required by the signal receiving unit and the processor.
5. The current sensing device according to claim 1, wherein the magnetic sensor, the signal receiving unit and the processor are disposed in a power device, and the power device is any one of the following: a non-contact power sensor, an electricity meter, a power socket, a power plug, a power converter, a power adapter, or a power extension cord.
6. The current sensing device of claim 1, further comprising:
the signal transmission unit is electrically connected to the processor, so that the processor can transmit the calculated value of the current to an external electronic device through the signal transmission unit;
the signal transmission unit is a wired transmission interface or a wireless transmission interface.
7. The current sensing device of claim 2, wherein the processor further comprises a microprocessor unit coupled to the active current computing unit.
8. The current sensing device of claim 3, further comprising:
an electromagnetic shielding layer covering the magnetic ring.
9. The current sensing device of claim 4, wherein the power supply unit is any one of: a battery, a power supply, a power converter, or a voltage regulator.
10. The current sensing device of claim 7, wherein the processor further comprises:
and the sensing current correction unit is coupled between the effective current operation unit and the microprocessor unit.
11. The current sensing device according to claim 10, wherein the sensed current correcting unit is capable of correcting the value of the current calculated by the effective current calculating unit based on the value of the current calculated by the effective current calculating unit and a value of a measured current measured by a current measuring device from the cable.
12. The current sensing device as claimed in claim 10, wherein the sensing current calibration unit is capable of calibrating the value of the current transmitted by the cable calculated by the effective current calculation unit based on the first magnetic field sensing signal and the second magnetic field sensing signal.
13. A method of current sensing, comprising the steps of:
(1) providing a current sensing device comprising at least one magnetic sensor, a signal receiving unit and a processor; wherein, the processor is provided with an environmental magnetic field filtering unit and an effective current operation unit;
(2) enabling the magnetic sensor to sense a first sensing magnetic field of a cable on an initial sensing position and outputting a first magnetic field sensing signal;
(3) the processor receives the first magnetic field sensing signal output by the magnetic sensor through the signal receiving unit;
(4) the ambient magnetic field filtering unit filters an ambient magnetic field component carried by the first magnetic field;
(5) the effective current computing unit computes a current value transmitted by the cable according to the first magnetic field sensing signal.
14. The current sensing device as claimed in claim 13, wherein the ambient magnetic field filtering unit performs the filtering of the ambient magnetic field component by using an ambient magnetic field filtering expression, and the ambient magnetic field filtering expression is represented by the following formula (1):
wherein n is an integer, IiIn order to take the current out of the current,
to filter out the current after the dc component.
15. The current sensing device as claimed in claim 14, wherein the effective current computing unit computes the value of the current transmitted by the cable by using an effective current expression, and the effective current expression is represented by the following formula (2):
wherein, IRMSRepresenting the effective value of the current.
16. The current sensing device as claimed in claim 15, wherein the processor further comprises a microprocessor unit coupled to the effective current computing unit, and the processor further comprises a sensing current calibration unit coupled between the effective current computing unit and the microprocessor unit.
17. The method of claim 16, further comprising the steps of:
(6) the sensing current correction unit can correct the value of the current calculated by the effective current calculation unit based on the value of the current calculated by the effective current calculation unit and a value of a measurement current measured by a current measurement device from the cable.
18. The method of claim 16, further comprising the steps of:
(6a) displacing the magnetic sensor to enable the magnetic sensor to be positioned on a first adjustment sensing position;
(7a) enabling the magnetic sensor to sense a second sensing magnetic field of the cable on the first adjustment sensing position and output a second magnetic field sensing signal, and then repeating the steps (3) to (5);
(8a) based on the first magnetic field sensing signal and the second magnetic field sensing signal, the sensing current correction unit corrects the value of the current transmitted by the cable calculated by the effective current calculation unit.
19. The current sensing device as claimed in claim 17, wherein the sensing current calibration unit calibrates the value of the current transmitted by the cable calculated by the effective current calculation unit by using a current calibration expression, and the current calibration expression is represented by the following formula (3):
ICal＝(IRMS)/k……………………….(3)；
wherein, ICalThe corrected value of the current, and k is a current correction parameter.
20. The current sensing device as claimed in claim 18, wherein the sensing current calibration unit calibrates the value of the current transmitted by the cable calculated by the effective current calculation unit by using a current calibration expression represented by the following formulas (3a) and (3 b):
wherein, ICalCorrected value of the current, mu0Is a vacuum permeability, BinR' is a corrected value of a distance between the initial sensing position and a wire inside the cable line, and d is a distance between the initial sensing position and the first adjusted sensing position.
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| CN102162819A (en) * | 2010-02-12 | 2011-08-24 | 阿尔卑斯绿色器件株式会社 | Current measuring device |
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