Electromagnetic direct current transformer
Through the combination of two electromagnetic current transformers and voltage sources, DC current measurement is achieved using the law of electromagnetic induction, which solves the problem that the existing technology cannot measure DC current, and achieves a low-cost and high-precision measurement effect.
Patent Information
- Application Number
- CN202411438394.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-15
- Publication Date
- 2024-12-24
AI Technical Summary
Existing electromagnetic current transformers cannot measure DC current, and existing alternative methods such as shunts, Hall current sensors, active electronic current transformers and optical current transformers have high cost and low cost performance.
Using a combination of two electromagnetic current transformers and voltage sources, through series connection between the primary and secondary sides, the DC current is measured using the law of electromagnetic induction. The frequency of the voltage source is much higher than the measured current, and full wave is effective The value RMS algorithm performs signal processing.
It realizes low-cost and high-precision DC current measurement, reduces measurement errors, improves measurement accuracy, and has a large price advantage.
Smart Images
Figure CN119178916A_ABST
Abstract
Description
[Technical field]
[0001] The invention relates to the technical field of current measurement, and in particular to an electromagnetic direct current transformer. [Background technology]
[0002] The electromagnetic current transformer is a special transformer. Based on Faraday's law of electromagnetic induction, the magnetic field generated by DC current does not change with time, so the electromagnetic current transformer cannot measure DC current.
[0003] At present, there are many methods for measuring DC current, such as shunts, Hall current sensors, active electronic (Rogowski coil) current transformers, optical current transformers, etc. However, the basic principle of the shunt is to measure the current through a low-resistance precision resistor (called a shunt resistor). The disadvantages are that in large current scenarios, the power consumption is large, the heat is high, and the temperature drift affects the measurement accuracy. The disadvantages of Hall current sensors, active electronic (Rogowski coil) current transformers, and optical current transformers are high cost and low cost performance. [Summary of the invention]
[0004] The embodiment of the present invention provides an electromagnetic direct current transformer, aiming to solve the technical problems existing in the electromagnetic current transformer in the related art.
[0005] In a first aspect, an embodiment of the present invention provides an electromagnetic DC current transformer connected between a current source and a measuring device, comprising: a first electromagnetic current transformer, a second electromagnetic current transformer and a voltage source;
[0006] The primary sides of the first electromagnetic current transformer and the second electromagnetic current transformer are sleeved on the conductor to be measured and connected to the current source, wherein the primary sides of the first electromagnetic current transformer and the second electromagnetic current transformer are connected in series with the same polarity, and the secondary sides are connected in series with opposite polarity;
[0007] The voltage source is connected to the measuring device, and the voltage source and the measuring device are connected to secondary sides of the first electromagnetic current transformer and the second electromagnetic current transformer.
[0008] In one embodiment, optionally, the first end of the primary side of the first electromagnetic current transformer is connected to the first end of the current source, the second end of the primary side of the first electromagnetic current transformer is connected to the first end of the primary side of the second electromagnetic current transformer, and the second end of the primary side of the second electromagnetic current transformer is connected to the second end of the current source.
[0009] In one embodiment, optionally, the first end of the secondary side of the first electromagnetic current transformer is connected to the first end of the voltage source, the second end of the secondary side of the first electromagnetic current transformer is connected to the second end of the secondary side of the second electromagnetic current transformer, the first end of the secondary side of the second electromagnetic current transformer is connected to the first end of the measuring device, and the second end of the measuring device is connected to the second end of the voltage source.
[0010] In one embodiment, optionally, the iron cores of the first electromagnetic current transformer and the second electromagnetic current transformer are independently provided.
[0011] In one embodiment, optionally, the iron cores of the first electromagnetic current transformer and the second electromagnetic current transformer are made of soft magnetic material.
[0012] In one embodiment, optionally, the electrical parameters of the first electromagnetic current transformer and the second electromagnetic current transformer are the same.
[0013] In one embodiment, optionally, a voltage peak value of the voltage source is less than a sum of saturation voltages of the first electromagnetic current transformer and the second electromagnetic current transformer.
[0014] In one embodiment, optionally, the saturation current of the first electromagnetic current transformer and the second electromagnetic current transformer is lower than a preset threshold.
[0015] In one embodiment, optionally, in the saturation region of the first electromagnetic current transformer and the second electromagnetic current transformer, the magnetic flux density B is approximately a constant.
[0016] In one embodiment, optionally, when the measured current of the measured conductor is alternating current, the first frequency of the voltage source is much higher than the second frequency of the measured current.
[0017] In one embodiment, optionally, the algorithm of the measuring device adopts the full-wave effective value RMS (Root meansquare).
[0018] The Root Mean Square (RMS) is a statistic used to measure the average value of a set of values. It is the square root of the average value after summing the squares of each value. RMS is often used to measure the amplitude of a waveform or the strength of a signal.
[0019] The specific steps for calculating RMS are as follows
[0020] 1. Square each value.
[0021] 2. Add up all the squared values.
[0022] 3. Divide the above result by the total number of values.
[0023] 4. Take the square root of the above result.
[0024] In signal processing, RMS is often used to calculate the effective value of a signal.
[0025] The electromagnetic DC current transformer in the present invention is connected between the current source and the measuring device, and includes: a first electromagnetic current transformer, a second electromagnetic current transformer and a voltage source; the primary side of the first electromagnetic current transformer and the second electromagnetic current transformer is sleeved on the conductor to be measured and connected to the current source, wherein the primary side of the first electromagnetic current transformer and the second electromagnetic current transformer are connected in series and have the same polarity, and the secondary side is connected in series and has opposite polarity; the voltage source is connected to the measuring device, and the voltage source and the measuring device are connected to the secondary side of the first electromagnetic current transformer and the second electromagnetic current transformer. In the present invention, two electromagnetic current transformers and a voltage source are used to realize the measurement of DC current through an electromagnetic current transformer. In this way, the electromagnetic DC current transformer is composed of existing mature devices, the device price is low, the overall cost has a large price advantage, and the measurement error is small and the accuracy is high.
Brief Description of the Drawings
[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0027] Figure 1 A module connection diagram of an electromagnetic DC current transformer according to an embodiment of the present invention is shown.
[0028] Figure 2 An example schematic diagram of a 7500A DC current waveform simulated by MATLAB / simulink software according to an embodiment of the present invention is shown.
[0029] Figure 3 A schematic diagram showing an example of a 7500A low-frequency AC current waveform simulated by MATLAB / simul ink software according to another embodiment of the present invention is shown. [Specific implementation method]
[0030] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.
[0031] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0032] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.
[0033] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.
[0034] See also Figure 1 , Figure 1 The structure diagram of an electromagnetic direct current transformer according to an embodiment of the present invention is shown. The electromagnetic direct current transformer is used to solve the technical problems existing in the related art.
[0035] like Figure 1 As shown, an electromagnetic DC current transformer according to an embodiment of the present invention is connected between a primary-side current source and a measuring device, and includes: a first electromagnetic current transformer CT1, a second electromagnetic current transformer CT2 and a voltage source E;
[0036] The primary sides of the first electromagnetic current transformer CT1 and the second electromagnetic current transformer CT2 are sleeved on the conductor to be measured and connected to the current source E, wherein the primary sides of the first electromagnetic current transformer CT1 and the second electromagnetic current transformer CT2 are connected in series with the same polarity, and the secondary sides are connected in series with opposite polarity;
[0037] The voltage source E is connected to the measuring device, and the voltage source E and the measuring device are connected to the secondary sides of the first electromagnetic current transformer CT1 and the second electromagnetic current transformer CT2.
[0038] In one embodiment, optionally, the first end of the primary side of the first electromagnetic current transformer is connected to the first end of the current source, the second end of the primary side of the first electromagnetic current transformer is connected to the first end of the primary side of the second electromagnetic current transformer, and the second end of the primary side of the second electromagnetic current transformer is connected to the second end of the current source.
[0039] In one embodiment, optionally, the first end of the secondary side of the first electromagnetic current transformer is connected to the first end of the voltage source, the second end of the secondary side of the first electromagnetic current transformer is connected to the second end of the secondary side of the second electromagnetic current transformer, the first end of the secondary side of the second electromagnetic current transformer is connected to the first end of the measuring device, and the second end of the measuring device is connected to the second end of the voltage source. Figure 1 As shown, CT1-P1 is opposite to CT2-P2; the secondary circuits CT1 and CT2 are connected in reverse series and then connected to the voltage source E, such as: CT1-S2 is connected to CT2-S2, CT1-S1 and CT2-S1 are connected to the voltage source E and both sides of the measuring device.
[0040] For the electromagnetic DC current transformer mentioned above, when the primary side is DC current, if no voltage source is applied, the primary current is completely converted into the excitation branch current, and both electromagnetic current transformers quickly enter the saturation state, and the secondary side current is zero. When the primary side is DC current, if a voltage source is properly applied, the two electromagnetic current transformers alternately enter the saturation state. At a certain moment, the inductance of the transformer in the saturated state drops to zero, and its terminal voltage is zero. The transformer in the unsaturated state will almost bear the entire voltage source voltage drop, and the voltage source forces the unsaturated transformer core magnetic flux density to drop to the unsaturated zone. For the current transformer in the unsaturated state, the electromagnetic induction law based on the transformer model is applicable, satisfying I1=N×I2+Ie, where I1 is the primary current, I2 is the secondary current, Ie is the excitation branch current, and N is the transformer ratio. When unsaturated, Ie≈0, and the secondary current N×I2 can reflect the primary current I1, so the two electromagnetic current transformers can alternately accurately measure the primary current.
[0041] In one embodiment, optionally, the iron cores of the first electromagnetic current transformer and the second electromagnetic current transformer are independently provided.
[0042] In one embodiment, optionally, the iron cores of the first electromagnetic current transformer and the second electromagnetic current transformer are made of soft magnetic material.
[0043] In this embodiment, the iron cores of the two electromagnetic current transformers are independently arranged and made of soft magnetic material, so that the hysteresis curve of the electromagnetic current transformer is a "thin" curve.
[0044] In one embodiment, optionally, the electrical parameters of the first electromagnetic current transformer and the second electromagnetic current transformer are the same.
[0045] In one embodiment, optionally, a voltage peak value of the voltage source is less than a sum of saturation voltages of the first electromagnetic current transformer and the second electromagnetic current transformer.
[0046] In this embodiment, the peak voltage of the voltage source is less than twice the saturation voltage of the electromagnetic current transformer.
[0047] In one embodiment, optionally, the saturation current of the first electromagnetic current transformer and the second electromagnetic current transformer is lower than a preset threshold.
[0048] In this embodiment, the saturation current of the electromagnetic current transformer should be as low as possible, and the saturation region of the electromagnetic current transformer requires the magnetic flux density B to increase as slowly as possible to facilitate rapid switching between the saturated and unsaturated states of the two sub-current transformers as quickly as possible.
[0049] In one embodiment, optionally, when the measured current of the measured conductor is alternating current, the first frequency of the voltage source is much higher than the second frequency of the measured current.
[0050] In one embodiment, optionally, the algorithm of the measuring device adopts the full-wave effective value RMS.
[0051] like Figure 2 As shown, it is the MATLAB / simulink software simulation test waveform example 1. In the figure, the voltage source frequency is 50Hz, the measured current is a DC with an amplitude of 7500A, and the secondary value current RMS*7500 is the measurement target value.
[0052] like Figure 3 As shown, it is the MATLAB / simulink software simulation test waveform example 2. In the figure, the voltage source frequency is 50Hz, the measured current is a low-frequency AC with a frequency of 1Hz and an amplitude of 7500A, and the secondary value current RMS*7500 is the measurement target value.
[0053] Through MATLAB / simul ink software simulation test, the measurement error is small and can be accurately calibrated through the later software of the measuring device.
[0054] It should be noted that the circuit function of the electromagnetic DC current transformer provided in this embodiment is mainly realized by the circuit connection relationship between each circuit module, and does not rely on the program module in a certain circuit module. In addition, each circuit module in the electromagnetic DC current transformer can be realized by an analog circuit or a digital circuit, and for the circuit module that can be implanted with a program module, the realization of its module function can be realized by the program module provided by the prior art.
[0055] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.
[0056] It should be understood that, although the terms first, second, etc. may be used to describe the setting units in the embodiments of the present invention, these setting units should not be limited to these terms. These terms are only used to distinguish the setting units from each other. For example, without departing from the scope of the embodiments of the present invention, the first setting unit may also be referred to as the second setting unit, and similarly, the second setting unit may also be referred to as the first setting unit.
[0057] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.
[0058] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, systems and methods can be implemented in other ways. For example, the system embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or units, which can be electrical, mechanical or other forms.
[0059] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of hardware plus software functional units.
[0060] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.
Claims
1. An electromagnetic DC current transformer, characterized in that: connected between the current source and the measuring device, comprising: a first electromagnetic current transformer, a second electromagnetic current transformer and a voltage source; The primary sides of the first electromagnetic current transformer and the second electromagnetic current transformer are sleeved on the conductor to be measured and connected to the current source, wherein the primary sides of the first electromagnetic current transformer and the second electromagnetic current transformer are connected in series with the same polarity, and the secondary sides are connected in series with opposite polarity; The voltage source is connected to the measuring device, and the voltage source and the measuring device are connected to secondary sides of the first electromagnetic current transformer and the second electromagnetic current transformer.
2. The electromagnetic DC current transformer according to claim 1, characterized in that: The first end of the primary side of the first electromagnetic current transformer is connected to the first end of the current source, the second end of the primary side of the first electromagnetic current transformer is connected to the first end of the primary side of the second electromagnetic current transformer, and the second end of the primary side of the second electromagnetic current transformer is connected to the second end of the current source.
3. The electromagnetic DC current transformer according to claim 1, characterized in that: The first end of the secondary side of the first electromagnetic current transformer is connected to the first end of the voltage source, the second end of the secondary side of the first electromagnetic current transformer is connected to the second end of the secondary side of the second electromagnetic current transformer, the first end of the secondary side of the second electromagnetic current transformer is connected to the first end of the measuring device, and the second end of the measuring device is connected to the second end of the voltage source.
4. The electromagnetic DC current transformer according to claim 1, characterized in that: The iron cores of the first electromagnetic current transformer and the second electromagnetic current transformer are independently arranged.
5. The electromagnetic DC current transformer according to claim 1, characterized in that: The iron cores of the first electromagnetic current transformer and the second electromagnetic current transformer are made of soft magnetic material.
6. The electromagnetic DC current transformer according to claim 1, characterized in that: The electrical parameters of the first electromagnetic current transformer and the second electromagnetic current transformer are the same.
7. The electromagnetic DC current transformer according to claim 1, characterized in that: A voltage peak value of the voltage source is smaller than a sum of saturation voltages of the first electromagnetic current transformer and the second electromagnetic current transformer.
8. The electromagnetic DC current transformer according to claim 1, characterized in that: The saturation current of the first electromagnetic current transformer and the second electromagnetic current transformer is lower than a preset threshold.
9. The electromagnetic DC current transformer according to claim 1, characterized in that: When the measured current of the measured conductor is alternating current, the first frequency of the voltage source is much higher than the second frequency of the measured current.
10. The electromagnetic DC current transformer according to claim 1, characterized in that: The algorithm of the measuring device uses the full-wave effective value RMS.