DANKERT, Mario (Am Lingenauer Wald 1, Raguhn-Jeßnitz, 06779, DE)
DU, Feng (Lane N° 1954, Hua Shan RD Xu Jia Hui, Shanghai 5, 20013, CN)
CHEN, Wei Gang (Room 305, Lane N° 197JuYe Rdan Rd. Pudong, Shanghai 5, 20013, CN)
ZHUO, Yue (Room 401, Gate1 Building South Zero,Tsinghua University, Beijing 4, 10008, CN)
MIN, Ying Zong (Room N° 73-601, Lane N° 399JuFeng Rd. Pudong, Shanghai 9, 20012, CN)
DANKERT, Mario (Am Lingenauer Wald 1, Raguhn-Jeßnitz, 06779, DE)
DU, Feng (Lane N° 1954, Hua Shan RD Xu Jia Hui, Shanghai 5, 20013, CN)
CHEN, Wei Gang (Room 305, Lane N° 197JuYe Rdan Rd. Pudong, Shanghai 5, 20013, CN)
ZHUO, Yue (Room 401, Gate1 Building South Zero,Tsinghua University, Beijing 4, 10008, CN)
| Claims 1. An apparatus for current measurement, comprising: a magnetic ring (12), through which can pass at least one conductor (11) for passing a current to be measured; a coil (10) disposed on said magnetic ring (12); a sampling resistor (14) which is electrically connectable to an end of said coil (10); a driving voltage source (18), with an output end thereof being electrically connectable to another end of said coil (10); and a comparator (16), with an output end thereof being electrically connectable to an input end of said driving voltage source (18); characterized in that said current measurement apparatus further comprises: a first feedback unit (30), said first feedback unit (30) being able to acquire a first feedback signal (111) from said sampling resistor (14), with the first feedback signal (111) being electrically connectable to another input end of said driving voltage source (18); and a second feedback unit (20), said second feedback unit (20) being able to acquire the first feedback signal (111) from said sampling resistor (14) and to obtain a second feedback signal after having the first feedback signal (111) processed by a differentiator, and the second feedback signal (112) being electrically connectable to an input end of said comparator (16). 2. The current measurement apparatus as claimed in claim 1, wherein a first preset value is set in said comparator (16), and the first preset value controls the output polarity of said driving voltage source (18), such that the reverse point of the output polarity of said driving voltage source (18) is set in a saturation region in which said magnetic ring (12) operates. 3. The current measurement apparatus as claimed in claim 2, wherein a second preset value is also set in said comparator (16), and said second preset value controls the output polarity of said driving voltage source for it not to be reversed. 4. The current measurement apparatus as claimed in claim 1, wherein the output voltage of said comparator (16) is a square wave voltage with a fixed amplitude. 5. The current measurement apparatus as claimed in claim 1, wherein said driving voltage source (18) further comprises an adder, and the output voltage of said comparator and a voltage signal of said first feedback unit (30) are input together into an input end of said adder. 6. The current measurement apparatus as claimed in claim 1, wherein a detection circuit (40) is also disposed therein, and said detection circuit (40) acquires the first feedback signal (111) from said sampling resistor (14) to obtain a current signal measured thereby. 7. A method for current measurement, comprising: generating, by a driving voltage, a drive current in a current measurement loop including a sampling resistor (14) and a coil (10); acquiring a first feedback signal (111) generated over the sampling resistor (14) by said drive current; utilizing a differential signal of the drive current as a second feedback signal (112); comparing the second feedback signal (112) with a preset value, and outputting an output voltage signal according to the comparison result; accumulating said first feedback signal (111) onto said output voltage signal to obtain said driving voltage; and controlling, by said output voltage signal, the polarity of said driving voltage. 8. The current measurement method as claimed in claim 7, wherein said preset value comprises a first preset value and a second preset value, when the differential signal of said drive current is the same as the first preset value, said voltage signal output causes said driving voltage to reverse; and when the differential signal of said drive current is in the remaining time domain except the one which is the same as the first preset value, the second preset value is used to prevent said driving voltage from being reversed. 9. The current measurement method as claimed in claim 7, wherein said output voltage signal is a square wave voltage signal with a fixed voltage amplitude. |
Current measurement apparatus and current measurement method thereof
Technical field
The present invention relates to a current measurement apparatus and a current measurement method thereof and, particularly to a current measurement apparatus and a current measurement method thereof based on the principle of magnetic modulation, which are especially suitable for the measurement of B class residual current of an AC and/or DC current.
Background art
AC and/or DC testing methods based on magnetic modulation technology have been applied widely, in which the operating state of a magnetic core is put alternatively into the linear and nonlinear regions of a magnetic core magnetization curve (also referred to as hysteresis curve, BH curve, and referred to as BH curve hereinbelow) as shown in Fig. 1 by way of a driving voltage source, and here it is very important to judge the intersection points of the linear region and the nonlinear regions in BH curve (as shown by the dashed circles in the figure) , and this is helpful to reverse the output voltage of the driving voltage source at a position close to the above-mentioned intersection in a nonlinear region.
European patent EP1212821 discloses an AC and/or DC current measurement apparatus based on magnetic modulation. In particular, a measured signal is modulated by an AC voltage driving signal generated by a driving voltage source, and since there is no relationship between the generation of the AC voltage driving signal and the measured signal, it is very difficult to control the operating state of the magnetic core. A limitation caused by this solution is that the material of selected magnetic core is required to have very good consistency, which results in relatively high costs for magnetic core material and processing and manufacturing thereof. Another limitation caused by this solution is that the magnetic core may be set in an over-saturation state, so it may result in relatively high power consumption. European patent EP1610133 discloses another AC and/or DC current measurement apparatus based on magnetic modulation. In this solution, a sampling resistor is serially connected to a coil, and when the voltage signal on this sampling resistor is higher than a preset value, the voltage driving source is reversed. Since the generation of AC voltage driving signal introduces a feedback signal, it reduces the consistency requirements of the magnetic core material.
However, this solution also has limitations, since the feedback signal cannot precisely reflect the change in the coil's inductance; when the current to be measured changes, the reverse turning point of the magnetic core will also change, and this may influence the accuracy of current measurement. In order to increase the current detection range and avoid the possibility of the turning point entering the linear region, this turning point has to be set as far away from the intersection of the linear region and the nonlinear region as possible, but this would result in relatively high power consumption. At the same time, this solution needs an amplifier apparatus connected to the input end of the
sampling resistor, which increases the circuit complexity.
Contents of the invention
An object of the present invention is to provide a current measurement apparatus, which apparatus is capable of locating the output voltage reverse control point of a driving voltage source set in the nonlinear region of the magnetic ring' s BH curve as close to the real intersection of the nonlinear region and the linear region as possible, so as to extend the measurement range of the current to be
measured, improve the measurement accuracy, and at the same time reduce the power consumption of the measurement
apparatus during a test. The present invention further provides a current
measurement method, which method is capable of locating the output voltage reverse control point of the driving voltage source set in the nonlinear region of the magnetic ring' s BH curve as close to the real intersection of the nonlinear region and the linear region as possible, thereby it can extend the measurement range of the current to be measured, improve the measurement accuracy, and at the same time reduce the power consumption of the measurement apparatus during a test.
The present invention provides a current measurement apparatus, comprising: a magnetic ring through which can pass a conductor for passing a current to be measured; a coil disposed on the magnetic ring; a sampling resistor which is electrically connectable to an end of the coil; a driving voltage source, with the output end thereof being
electrically connectable to another end of the coil; a comparator, with the output end thereof being electrically connectable to an input end of the driving voltage source; a first feedback unit, which can acquire a first feedback signal from the sampling resistor, with the first feedback signal being electrically connectable to another input end of the driving voltage source; and a second feedback unit, which can acquire the first feedback signal from said sampling resistor to obtain a second feedback signal after having the first feedback signal processed differentially, with the second feedback signal being electrically connectable to an input end of the comparator.
In another illustrative embodiment of the current
measurement apparatus, a first preset value is set in the comparator, and the first preset value controls the polarity of said driving voltage to cause the polarity reverse point of the driving voltage to be set in a saturation region in which said magnetic ring operates. A second preset value is also set in the comparator, and the second preset value controls the polarity of the driving voltage for it not to be reversed, wherein the second preset value can be greater than or equal to the first preset value.
In another illustrative embodiment of the current
measurement apparatus, the output voltage of the comparator is a square wave voltage with a fixed amplitude.
In yet another illustrative embodiment of the current measurement apparatus, the driving voltage source further comprises an adder, and the output voltage of the adder and the voltage signal of the first feedback unit are input together into an input end of the adder to obtain a driving voltage after having then accumulated. In yet another illustrative embodiment of the current measurement apparatus, a detection circuit can also be disposed therein to acquire the first feedback signal from the sampling resistor. The present invention further provides a current
measurement method, comprising: generating a drive current in a current measurement loop including a sampling resistor and a coil; acquiring a first feedback signal generated over the sampling resistor by said drive current; utilizing a
differential signal of the drive current as a second feedback signal; comparing the second feedback signal with a preset value and outputting an output driving signal according to the comparison result; controlling the polarity of the driving voltage by using the output voltage signal; and accumulating the first feedback signal onto said output voltage signal to obtain said driving voltage.
In yet another illustrative embodiment of the current measurement method, the preset value can include a first preset value and a second preset value, when said second feedback signal is the same as the first feedback signal, said voltage signal output reverses said driving voltage; and when said second feedback signal is in the remaining time domain except the one which is the same as the first preset value, the second preset value is used to prevent the driving voltage from being reversed. In yet another illustrative embodiment of the current measurement method, the output voltage signal is a square wave voltage signal with a fixed voltage amplitude.
When using the current measurement apparatus and the current measurement method of the present invention, the amplitude of the driving voltage is controlled by the voltage signal over the sampling resistor so as to control the magnitude of the drive current, and the operating state of magnetic core has no relationship with the current to be measured, therefore, for the current to be measured, there is a relatively wide range of current measurement.
When using the current measurement apparatus and the current measurement method of the present invention, since the operating time of magnetic core under saturation is reduced, the power consumption during measurement can be effectively reduced.
Furthermore, since the reverse control point of the driving voltage is set in the nonlinear region close to the real intersection of the linear region and the nonlinear region of magnetic core's BH curve, and this reverse control point has no relationship with the current to be measured, therefore, the measurement apparatus and method of the present invention have relatively high measurement accuracy.
Moreover, since the reverse control point of the polarity of the driving voltage is set in the nonlinear region of the magnetic core's BH curve, automatic magnetic reset can be achieved by employing the current measurement apparatus and method of the present invention.
Brief description of the accompanying drawings Fig. 1 is an illustrative diagram of the BH curve of a magnetic ring.
Fig. 2 is an illustrative diagram of the circuit
structure of an illustrative embodiment of a current
measurement apparatus of the present invention.
Fig. 3 is an illustrative diagram of the circuit
structure of a particular illustrative embodiment of the current measurement apparatus in Fig. 2.
Fig. 4 is an equivalent circuit of the circuit in Fig. 2. Fig. 5 is an illustrative diagram of the timing
relationship in the circuit shown in Fig. 2.
Description of reference numerals
10 coil 11 conductor 12 magnetic ring 14
sampling resistor
16 comparator 18 driving voltage source 20 second feedback unit
30 first feedback unit 40 detection circuit Exemplary embodiments
For the sake of better understanding the technical features, objects and effects of the present invention, particular embodiments of the present invention will now be described by reference to the accompanying drawings, and in the drawings like numerals refer to components with the same structure or with similar structure but the same function.
Fig. 2 is an illustrative embodiment of a current
measurement apparatus of the present invention, which
apparatus comprises a magnetic ring 12, a coil 10, a sampling resistor 14, a driving voltage source 18, a comparator 16, a first feedback unit 30 and a second feedback unit 20.
A conductor 11, through which a current (DC or AC) to be measured can pass, passes through the magnetic ring 12, the coil 10 is wound around the magnetic ring 12, the sampling resistor 14 is serially connected to an end of the coil 10, another end of the coil 10 is electrically connectable to an output end of the driving voltage source 18, and the driving voltage source 18 outputs a driving voltage U e 2 and generates a drive current i in the sampling resistor 14 and the coil 10. The output voltage at the output end of the comparator 16 is U e 3, which is electrically connectable to an input end of the driving voltage source 18.
In the current measurement apparatus, the first feedback unit 30 acquires a first feedback signal 111 from the
sampling resistor 14, in the illustrative embodiment shown in fig. 2, the first feedback signal 111 is a voltage signal, i.e. iR, and the first feedback signal 111 is inputted into an input end of the driving voltage source 18. The second feedback unit 20 can also acquire the first feedback signal 111, in the illustrative embodiment shown in fig. 2, the first feedback signal 111 is a voltage signal, i.e. iR, and the second feedback unit 20 generates a second feedback signal 112, i.e. the differential signal of the drive current i, after having the current signal therein processed differentially, and then the second feedback signal 112 is inputted into an input end of the comparator 16. The second feedback unit 20 is used to control the polarity of the driving voltage U e 2 outputted by the driving voltage source 18, while the first feedback unit 30 and the second feedback unit 20 are overlapped to control the output voltage signal of the driving voltage U e 2 outputted by the driving voltage source 18. Those skilled in the art would understand that the second feedback unit can achieve the differentiation of the drive current i by a differentiator.
Fig. 3 is an illustrative diagram of the circuit
structure of a particular illustrative embodiment of the current measurement apparatus in fig. 2. It includes a magnetic ring 12, a coil 10, a sampling resistor 14, a driving voltage source 18, a comparator 16, a first feedback unit 30, a second feedback unit 20 and a detection circuit 40. Herein, a first feedback module 20 is provided with a differentiator, the driving voltage source 50 is provided with an adder, and the output voltage at the output end of the comparator 16 and the voltage signal of a second feedback module 30 are input together into an input end of the adder.
Fig. 4 is an equivalent circuit of the circuit in fig. 2, if U e 2 is set to be the driving voltage of the driving voltage source 18, ¾ is the output voltage of the
comparator 16, R is the resistance value of the sampling resistor 14, L is the inductance of the coil 60, then:
U e2 = iR + Li Equation (2)
at the same time U e2 =U e3 + iR Equation (3)
in Equation (2) and Equation (3), i represents the drive current, i represents the differential of i.
From Equation (2) and Equation (3) it can be deduced that:
i =U e IL Equation (4) . Since U e s is the square wave voltage outputted by the comparator 16 in Equation (4) and the amplitude of U e s is a constant, when the magnetic core operates into the nonlinear region (saturation region) , the inductance L of the magnetic ring will be reduced to a very small value rapidly, making i increase rapidly, the transition of the linear region and nonlinear region in the BH curve of the magnetic ring as shown in fig. 1 can be reflected by way of the monitoring of i by the second feedback unit 20, and when the control point corresponding to the reverse of the driving voltage is set in the nonlinear region, it can be very close to the
intersection of the real linear region and nonlinear region.
The current i is related to the current to be measured in the conductor 11, since the amplitude of U e s in Equation (3) is a constant, the current i is only related to the amplitude of the output voltage of the driving voltage source 18, therefore, using such a current measurement method and a current measurement apparatus using this method, it would have a relatively wide range for current measurement.
When using a current measurement method and a current measurement apparatus using this method, since the reverse control point of the driving voltage is set in the nonlinear region close to the intersection of the real linear region and the nonlinear region of the magnetic core's BH curve, the saturation time of magnetic core is reduced, which can effectively reduce power consumption.
When using a current measurement method and a current measurement apparatus using this method, since the reverse control point of the driving voltage is set in the nonlinear region in the magnetic core's BH curve, automatic magnetic reset can be achieved.
In the illustrative embodiment shown in fig. 2, two preset values can be set in the comparator 16: a first preset value and a second preset value, in which the second preset value is greater than the first preset value (referring to fig. 5), and when measuring the current, at the time the first preset value (forward or backward) is the same as the output value i of the second feedback unit 20, the output signal of the comparator 22 reverses the driving voltage U e 2 generated in the driving voltage source 50. In the embodiment shown in fig. 5, the second preset value is far greater than the first preset value, in the entire time domain, the output value i of the second feedback unit 20 cannot be the same as the second preset value, therefore, the second preset value can control the driving voltage source U e 2 to be in the remaining time domain other than the one with i being the same as the first preset value, and the driving voltage U e 2 cannot be reversed. The sum of the voltage over the sampling resistor and the output voltage of the comparator is set to equal to the driving voltage U e 2. Those skilled in the art would understand that the selection of the first preset value is related to the
distance between the driving voltage reverse point and the turning point of the real linear region and the nonlinear region in the magnetic core's BH curve, which can be adjusted according to needs. Furthermore, taking the offset and polarity of the preset value into consideration, the first preset value can also be greater than, equal to or smaller than the second preset value.
In an illustrative embodiment shown in fig. 2, the output signal of the comparator 22 is a square wave voltage U e s with a fixed amplitude, the square wave voltage U e s can control the polarity of the driving voltage, and when the square wave voltage U e s is reversed, the driving voltage U e 2 is reversed at the same time.
In an illustrative embodiment, the driving voltage source 18 further comprises an adder (not shown in the figure) , the output signal U e s of the comparator 16 and the voltage signal of the first feedback unit 30 are inputted together into an input end of the adder, and the sum of the output signal U e s of the comparator 16 and the voltage signal U e 2 of the first feedback unit 30 is equal to the driving voltage outputted by the driving voltage source 18.
Those skilled in the art would understand that the adder in the driving voltage source 18 can input the input signals of the first feedback unit and the second feedback unit into an input end of the adder and can also respectively input the input signals of the first feedback unit and the second feedback unit into the two input ends of the adder, then the accumulation of the output signals of the first feedback unit and the second feedback unit can be achieved by any of these two manners.
Furthermore, in an illustrative embodiment, a detection circuit 40 is also disposed in the current measurement apparatus, and this detection circuit acquires the voltage signal over the sampling resistor 14 to obtain a current signal measured thereby. This detection circuit 40 can further comprise a low-pass filter (not identified in the figure), such as a Butterworth filter.
When using a current measurement method and a current measurement apparatus using this method, the change of the coil inductance can be precisely reflected by a feedback signal, and when the current to be measured changes, the change of the reverse turning point of the magnetic core can be precisely reflected, therefore, it has very high current measurement accuracy. In the present specification, "illustrative" means
"acting as an example, an instance or an illustration", and any diagram described as "illustrative" in the present document is not to be interpreted as a more preferred or more advantageous technical solution.
It should be understood that although the present
description is described by means of embodiments, it is not one technical solution which includes only one embodiment, and in this manner, the explanation in the description is only for the sake of clarity; those skilled in the art should take the description as a whole, and the technical solutions disclosed in the embodiments can be combined appropriately to form other embodiments which can be understood by those skilled in the art.
The detailed description set forth above is only directed to the particular description of the viable embodiments of the present invention, which are not intended to limit the protective scope of the present invention, and equivalent embodiments or variations made without departing from the technical spirit of the present invention shall be included in the protective scope of the present invention.