A current transformer

Abstract

The utility model discloses a current transformer, include: closed iron core, first I-V conversion circuit, first signal conditioning circuit, drive circuit, second I-V conversion circuit, second signal conditioning circuit, AD conversion circuit and treater, be equipped with first winding and second winding on closed iron core, the both ends of first winding are electrically connected with first I-V conversion circuit, and first I-V conversion circuit is electrically connected with first signal conditioning circuit, and first signal conditioning circuit is electrically connected with drive circuit, and drive circuit is electrically connected with one end of second winding, and the other end of second winding is electrically connected with second I-V conversion circuit, and second I-V conversion circuit is electrically connected with second signal conditioning circuit, and second signal conditioning circuit is electrically connected with AD conversion circuit, and AD conversion circuit is electrically connected with treater, the utility model solves the technical problem that the precision of existing mutual inductor is poor, and the anti -interference ability is weak and can not adapt the inside space size of circuit breaker.

Description

Technical Field

[0001] This utility model relates to the field of current transformer technology, and in particular to a current transformer. Background Technology

[0002] A current transformer is an instrument that measures current by converting a large primary current into a small secondary current based on the principle of electromagnetic induction. A current transformer consists of a closed iron core and windings. Its primary winding has very few turns and is connected in series with the circuit whose current needs to be measured; therefore, the entire current of the circuit often flows through it. The secondary winding has more turns and is connected in series with the measuring instrument and protection circuit. During operation, the secondary circuit of the current transformer is always closed. Therefore, the impedance of the series coils of the measuring instrument and protection circuit is very small, and the operating state of the current transformer is close to a short circuit. Currently, existing low-voltage circuit breakers are increasingly trending towards miniaturization, carrying larger currents, and having smaller structural dimensions. Therefore, the current transformers inside circuit breakers must be both small in size and capable of high-precision measurement of large currents. Conventional methods for current measurement include using Hall effect sensors or Rogowski coils. Hall effect sensors suffer from large temperature drift across the entire temperature range, resulting in poor overall accuracy. Rogowski coils, on the other hand, exhibit poor accuracy at low currents and are susceptible to interference. Conventional iron-core current transformers, limited by the cross-sectional area of ​​the iron core, saturate at high currents, failing to meet the requirements for high-current measurements. Therefore, there is an urgent need to develop a new current transformer that addresses the technical problems of poor accuracy, weak anti-interference capabilities, and inability to adapt to the internal space dimensions of circuit breakers. Utility Model Content

[0003] The main purpose of this invention is to propose a current transformer that aims to solve the technical problems of poor accuracy, weak anti-interference ability, and inability to adapt to the internal space size of existing transformers.

[0004] To achieve the above objectives, this utility model provides a current transformer, wherein the current transformer includes: a closed iron core, a first IV conversion circuit, a first signal conditioning circuit, a drive circuit, a second IV conversion circuit, a second signal conditioning circuit, an analog-to-digital converter circuit, and a processor; the closed iron core is provided with a first winding and a second winding; both ends of the first winding are electrically connected to the input terminal of the first IV conversion circuit, the output terminal of the first IV conversion circuit is electrically connected to the input terminal of the first signal conditioning circuit, the output terminal of the first signal conditioning circuit is electrically connected to the input terminal of the drive circuit, the output terminal of the drive circuit is electrically connected to one end of the second winding, the other end of the second winding is electrically connected to the input terminal of the second IV conversion circuit, the output terminal of the second IV conversion circuit is electrically connected to the input terminal of the second signal conditioning circuit, the output terminal of the second signal conditioning circuit is electrically connected to the analog-to-digital converter circuit, and the analog-to-digital converter circuit is electrically connected to the processor.

[0005] In one preferred embodiment, the first IV conversion circuit includes an operational amplifier U1, a resistor R1, and a capacitor C1; the inverting input terminal of the operational amplifier U1 is connected to the resistor R1, the capacitor C1, and one end of the first winding, respectively; the non-inverting input terminal of the operational amplifier U1 is connected to the other end of the first winding and ground, respectively; and the output terminal of the operational amplifier U1 is connected to the first signal conditioning circuit and the other end of the resistor R1 and the capacitor C1, respectively.

[0006] In one preferred embodiment, the first signal conditioning circuit includes an operational amplifier U2, a resistor R2, a capacitor C2, a resistor R3, and a first filter circuit; the inverting input terminal of the operational amplifier U2 is connected to the resistor R2, the resistor R3, and the capacitor C2 respectively; the other end of the resistor R2 is connected to the first IV conversion circuit; the non-inverting input terminal of the operational amplifier U2 is connected to the first filter circuit; the other end of the first filter circuit is grounded; and the output terminal of the operational amplifier U2 is connected to the resistor R3, the capacitor C2, and the driving circuit respectively.

[0007] In one preferred embodiment, the first filter circuit includes resistor R4, resistor R5 and capacitor C3. One end of resistor R4 is connected to the non-inverting input of operational amplifier U2, resistor R5 and capacitor C3, the other end of resistor R5 is connected to capacitor C3, and the other end of resistor R4 is grounded.

[0008] In one preferred embodiment, the driving circuit includes transistors Q1 and Q2; the base of transistor Q1 is connected to the first signal conditioning circuit and the base of transistor Q2, respectively; the collector of transistor Q1 is connected to the positive terminal of the power supply; the emitter of transistor Q1 is connected to the second winding and the emitter of transistor Q2, respectively; and the collector of transistor Q2 is connected to the negative terminal of the power supply.

[0009] In one preferred embodiment, the second IV conversion circuit includes an operational amplifier U3, a capacitor C4, and a resistor R6; the inverting input terminal of the operational amplifier U3 is connected to the resistor R6, the capacitor C4, and the second winding, respectively; the non-inverting input terminal of the operational amplifier U3 is grounded; and the output terminal of the operational amplifier U3 is connected to the other end of the resistor R6, the capacitor C4, and the second signal conditioning circuit, respectively.

[0010] In one preferred embodiment, the second signal conditioning circuit includes an operational amplifier U4, resistors R7 and R8, capacitor C5, and a second filter circuit. The inverting input of the operational amplifier U4 is connected to resistors R7, R8, and C5, respectively. The other end of resistor R7 is connected to a second IV conversion circuit. The non-inverting input of the operational amplifier U4 is connected to the second filter circuit. The other end of the second filter circuit is connected to ground and an analog-to-digital converter circuit, respectively. The output of the operational amplifier U4 is connected to resistor R8, capacitor C5, and the analog-to-digital converter circuit, respectively.

[0011] In one preferred embodiment, the second filter circuit includes resistor R9, resistor R10, and capacitor C6; one end of resistor R9 is connected to resistor R10, capacitor C6, and the non-inverting input terminal of operational amplifier U4, the other end of resistor R10 and capacitor C6 is connected to analog-to-digital converter circuit, and the other end of resistor R9 is grounded.

[0012] In the above-described technical solution of this utility model, the current transformer includes a closed iron core, a first IV conversion circuit, a first signal conditioning circuit, a drive circuit, a second IV conversion circuit, a second signal conditioning circuit, and an analog-to-digital conversion circuit. The closed iron core is provided with a first winding and a second winding. Both ends of the first winding are connected to the first IV conversion circuit, which is connected to the first signal conditioning circuit. The first signal conditioning circuit is connected to the drive circuit. The drive circuit is connected to one end of the second winding, and the other end of the second winding is connected to the second IV conversion circuit. The second IV conversion circuit is connected to the second signal conditioning circuit, and the second signal conditioning circuit is connected to the analog-to-digital conversion circuit. This utility model has a simple structure, small size, and low cost, solving the technical problems of poor accuracy, weak anti-interference ability, and inability to adapt to the internal space dimensions of existing current transformers. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0014] Figure 1 This is a first schematic diagram of a current transformer according to an embodiment of the present invention;

[0015] Figure 2 This is a second schematic diagram of a current transformer according to an embodiment of the present invention.

[0016] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of this utility model are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0019] Furthermore, in this utility model, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0020] Furthermore, the technical solutions of the various embodiments of this utility model can be combined with each other, but only if they are based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0021] See Figures 1-2 According to one aspect of this utility model, a current transformer is provided, wherein the current transformer includes: a closed iron core, a first IV conversion circuit, a first signal conditioning circuit, a drive circuit, a second IV conversion circuit, a second signal conditioning circuit, an analog-to-digital conversion circuit, and a processor; the closed iron core is provided with a first winding and a second winding; both ends of the first winding are electrically connected to the input terminal of the first IV conversion circuit, the output terminal of the first IV conversion circuit is electrically connected to the input terminal of the first signal conditioning circuit, the output terminal of the first signal conditioning circuit is electrically connected to the input terminal of the drive circuit, the output terminal of the drive circuit is electrically connected to one end of the second winding, the other end of the second winding is electrically connected to the input terminal of the second IV conversion circuit, the output terminal of the second IV conversion circuit is electrically connected to the input terminal of the second signal conditioning circuit, the output terminal of the second signal conditioning circuit is electrically connected to the analog-to-digital conversion circuit, and the analog-to-digital conversion circuit is electrically connected to the processor.

[0022] Specifically, in this embodiment, neither the first winding nor the second winding needs to be equipped with a sampling resistor. This reduces the load on the winding and avoids the problem of increased resistance value caused by resistor heating under high current, which leads to increased measurement error. At the same time, it eliminates the need for a precision resistor at this location, reducing costs. This not only helps improve measurement accuracy but also facilitates high current measurement.

[0023] Specifically, in this embodiment, the first IV conversion circuit includes an operational amplifier U1, a resistor R1, and a capacitor C1; the inverting input terminal of the operational amplifier U1 is connected to the resistor R1, the capacitor C1, and one end of the first winding, respectively; the non-inverting input terminal of the operational amplifier U1 is connected to the other end of the first winding and ground, respectively; the output terminal of the operational amplifier U1 is connected to the first signal conditioning circuit and the other end of the resistor R1 and the capacitor C1, respectively. The first IV conversion circuit is used to convert the current signal generated by electromagnetic induction in the closed iron core into a corresponding voltage signal. The primary circuit passes through the closed iron core, which is provided with a first winding and a second winding. The two ends of the first winding are connected to the first IV conversion circuit.

[0024] Specifically, in this embodiment, the first signal conditioning circuit includes an operational amplifier U2, a resistor R2, a capacitor C2, a resistor R3, and a first filter circuit; the inverting input terminal of the operational amplifier U2 is connected to the resistor R2, the resistor R3, and the capacitor C2 respectively, the other end of the resistor R2 is connected to the first IV conversion circuit, the non-inverting input terminal of the operational amplifier U2 is connected to the first filter circuit, the other end of the first filter circuit is grounded, and the output terminal of the operational amplifier U2 is connected to the resistor R3, the capacitor C2, and the driving circuit respectively; the first signal conditioning circuit is used to modulate the corresponding voltage signal to generate a driving signal.

[0025] Specifically, in this embodiment, the first filter circuit includes resistor R4, resistor R5, and capacitor C3. One end of resistor R4 is connected to the non-inverting input of operational amplifier U2, resistor R5, and capacitor C3. The other end of resistor R5 and capacitor C3 are connected to a reference point, and the other end of resistor R4 is grounded. By connecting the first filter circuit to the non-inverting input of operational amplifier U2, high-frequency noise can be effectively filtered out, while the resistors play a role in signal gain. At the same time, the output voltage signal reference is limited to the reference point REF, thereby improving the stability and reliability of the circuit.

[0026] Specifically, in this embodiment, the driving circuit includes transistors Q1 and Q2; the base of transistor Q1 is connected to both the first signal conditioning circuit and the base of transistor Q2, the collector of transistor Q1 is connected to the positive terminal of the power supply, the emitter of transistor Q1 is connected to both the second winding and the emitter of transistor Q2, and the collector of transistor Q2 is connected to the negative terminal of the power supply; the driving circuit is used to generate a corresponding driving current according to the driving signal and send the driving current into the second winding.

[0027] Specifically, in this embodiment, the second IV conversion circuit includes an operational amplifier U3, a capacitor C4, and a resistor R6; the inverting input terminal of the operational amplifier U3 is connected to the resistor R6, the capacitor C4, and the second winding, respectively; the non-inverting input terminal of the operational amplifier U3 is grounded; and the output terminal of the operational amplifier U3 is connected to the other end of the resistor R6, the capacitor C4, and the second signal conditioning circuit, respectively; the second IV conversion circuit is used to acquire the sampling current signal of the second winding and convert it into a corresponding sampling voltage signal.

[0028] Specifically, in this embodiment, the second signal conditioning circuit includes an operational amplifier U4, resistors R7 and R8, capacitor C5, and a second filter circuit. The inverting input of the operational amplifier U4 is connected to resistors R7, R8, and C5, respectively. The other end of resistor R7 is connected to a second IV conversion circuit. The non-inverting input of the operational amplifier U4 is connected to the second filter circuit. The other end of the second filter circuit is connected to ground and the analog-to-digital converter circuit, respectively. The output of the operational amplifier U4 is connected to resistor R8, capacitor C5, and the analog-to-digital converter circuit. After the second signal conditioning circuit performs gain filtering conditioning on the sampled voltage signal, it transmits it to the analog-to-digital converter circuit for AD conversion.

[0029] Specifically, in this embodiment, the second filter circuit includes resistor R9, resistor R10, and capacitor C6; one end of resistor R9 is connected to resistor R10, capacitor C6, and the non-inverting input of operational amplifier U4, the other end of resistor R10 and capacitor C6 is connected to the analog-to-digital converter circuit, and the other end of resistor R9 is grounded; by connecting the second filter circuit to the non-inverting input of operational amplifier U4, high-frequency noise can be effectively filtered out, while the resistor plays the role of signal gain, and at the same time, the output voltage signal reference is limited to the reference point REF, thereby improving the stability and reliability of the circuit.

[0030] Specifically, in this embodiment, the current transformer further includes a processor connected to an analog-to-digital converter (ADC). The ADC converts the voltage signal into an analog signal and transmits it to the processor to complete the current measurement and achieve current protection. In this invention, the processor uses an ACM32F070 MCU, the ADC uses an AD7606 ADC, and the operational amplifier uses a TP2311 operational amplifier. This invention is not specifically limited and can be configured as needed.

[0031] Specifically, in this embodiment, when current flows through the primary circuit, a magnetic field proportional to the primary current is generated according to the principle of electromagnetic induction. At this time, the first winding induces a secondary current proportional to the primary circuit current through the principle of electromagnetic induction. This secondary current is converted into a corresponding voltage signal by the first IV conversion circuit. The corresponding voltage signal is sent to the first signal conditioning circuit, which modulates a corresponding drive signal and sends it to the drive circuit. Through the drive circuit, a corresponding drive current is generated according to the corresponding drive signal and sent to the second winding. The direction of this drive current is opposite to that of the primary current, and the magnitude of the current is equal to the primary current divided by the number of turns of the second winding. A current flows through the second winding, thus generating a magnetic field. The magnitude of this magnetic field is the same as, but opposite in direction to, the magnetic field generated by the primary circuit, thereby canceling out the magnetic field generated by the current in the primary circuit and making the magnetic flux in the entire iron core zero. At this time, the induced current in the first winding becomes zero, and the corresponding drive signal generated by the signal modulation circuit also becomes zero. Therefore, when the current in the primary circuit changes, the secondary circuit always outputs a signal proportional to the reverse of the primary current signal through the first signal conditioning circuit and the drive circuit, canceling out the magnetic field and maintaining zero magnetic flux in the closed iron core. The second IV conversion circuit connected to the secondary winding circuit converts the second circuit's... The current is converted into voltage. The voltage signal is proportional to the current flowing through the second winding and also proportional to the primary circuit current signal, but in the opposite direction. The sampled voltage signal is then subjected to gain filtering and conditioning by the second signal conditioning circuit before being sent to the analog-to-digital converter (ADC) for A / D conversion, and finally to the processor to measure the primary circuit current and implement current protection. During operation, the magnetic field generated by the primary circuit current cancels out the magnetic field generated by the driving current in the second winding, resulting in zero magnetic flux in the closed core. Therefore, even if the primary circuit current is large, the problem of insufficient cross-sectional area of ​​the closed core will not cause issues. Magnetic saturation can occur, leading to inaccurate high-current measurements. Therefore, a smaller iron core can be used to achieve high-current detection. Furthermore, due to real-time modulation, it is also suitable for measuring fast-response current signals, thus saving material costs. Simultaneously, the closed-core structure ensures high measurement accuracy and strong anti-interference capabilities, making it suitable for high-precision measurements across the entire current range, from small to large currents. Its maximum measurement range can reach 15 times the rated current, allowing the current transformer to be used for both measurement and protection without the need for two independent current transformers. This makes it suitable for compact circuit breakers, helping to reduce circuit breaker size and lower product costs.

[0032] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural transformations made based on the inventive concept of this utility model and the contents of this utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this utility model.

Claims

1. A current transformer, characterized in that, include: The system comprises a closed iron core, a first IV conversion circuit, a first signal conditioning circuit, a drive circuit, a second IV conversion circuit, a second signal conditioning circuit, an analog-to-digital conversion circuit, and a processor; the closed iron core is provided with a first winding and a second winding. The two ends of the first winding are electrically connected to the input of the first IV conversion circuit. The output of the first IV conversion circuit is electrically connected to the input of the first signal conditioning circuit. The output of the first signal conditioning circuit is electrically connected to the input of the drive circuit. The output of the drive circuit is electrically connected to one end of the second winding. The other end of the second winding is electrically connected to the input of the second IV conversion circuit. The output of the second IV conversion circuit is electrically connected to the input of the second signal conditioning circuit. The output of the second signal conditioning circuit is electrically connected to the analog-to-digital conversion circuit. The analog-to-digital conversion circuit is electrically connected to the processor.

2. A current transformer according to claim 1, characterized in that, The first IV conversion circuit includes an operational amplifier U1, a resistor R1, and a capacitor C1; The inverting input terminal of the operational amplifier U1 is connected to the resistor R1, the capacitor C1 and one end of the first winding, respectively. The non-inverting input terminal of the operational amplifier U1 is connected to the other end of the first winding and the ground terminal, respectively. The output terminal of the operational amplifier U1 is connected to the first signal conditioning circuit and the other end of the resistor R1 and the capacitor C1, respectively.

3. A current transformer according to any one of claims 1-2, characterized in that, The first signal conditioning circuit includes an operational amplifier U2, a resistor R2, a capacitor C2, a resistor R3, and a first filter circuit. The inverting input terminal of the operational amplifier U2 is connected to the resistor R2, the resistor R3, and the capacitor C2, respectively. The other end of the resistor R2 is connected to the first IV conversion circuit. The non-inverting input terminal of the operational amplifier U2 is connected to the first filter circuit. The other end of the first filter circuit is grounded. The output terminal of the operational amplifier U2 is connected to the resistor R3, the capacitor C2, and the driving circuit, respectively.

4. A current transformer according to claim 3, characterized in that, The first filter circuit includes resistor R4, resistor R5 and capacitor C3. One end of resistor R4 is connected to the non-inverting input of operational amplifier U2, resistor R5 and capacitor C3, the other end of resistor R5 is connected to capacitor C3, and the other end of resistor R4 is grounded.

5. A current transformer according to any one of claims 1-2, characterized in that, The driving circuit includes transistors Q1 and Q2; the base of transistor Q1 is connected to the first signal conditioning circuit and the base of transistor Q2, respectively; the collector of transistor Q1 is connected to the positive terminal of the power supply; the emitter of transistor Q1 is connected to the second winding and the emitter of transistor Q2, respectively; and the collector of transistor Q2 is connected to the negative terminal of the power supply.

6. A current transformer according to any one of claims 1-2, characterized in that, The second IV conversion circuit includes an operational amplifier U3, a capacitor C4, and a resistor R6; the inverting input terminal of the operational amplifier U3 is connected to the resistor R6, the capacitor C4, and the second winding, respectively; the non-inverting input terminal of the operational amplifier U3 is grounded; and the output terminal of the operational amplifier U3 is connected to the other end of the resistor R6, the capacitor C4, and the second signal conditioning circuit, respectively.

7. A current transformer according to any one of claims 1-2, characterized in that, The second signal conditioning circuit includes an operational amplifier U4, resistors R7 and R8, capacitor C5, and a second filter circuit. The inverting input of the operational amplifier U4 is connected to resistors R7, R8, and C5, respectively. The other end of resistor R7 is connected to a second IV conversion circuit. The non-inverting input of the operational amplifier U4 is connected to the second filter circuit. The other end of the second filter circuit is connected to ground and an analog-to-digital converter circuit, respectively. The output of the operational amplifier U4 is connected to resistor R8, capacitor C5, and the analog-to-digital converter circuit, respectively.

8. A current transformer according to claim 7, characterized in that, The second filter circuit includes resistor R9, resistor R10, and capacitor C6; one end of resistor R9 is connected to resistor R10, capacitor C6, and the non-inverting input of operational amplifier U4, the other end of resistor R10 and capacitor C6 is connected to analog-to-digital converter circuit, and the other end of resistor R9 is grounded.

Images