Three-phase four-wire AC voltage acquisition circuit

Abstract

The utility model discloses a three-phase four-wire system AC voltage acquisition circuit, which comprises a differential amplification circuit, a high-value resistance network and a voltage reference circuit, and is characterized in that the differential amplification circuit comprises three differential amplifiers, namely a first differential amplifier, a second differential amplifier and a third differential amplifier; the voltage reference circuit is used for lifting a null line; the high-value resistance network comprises a residual voltage bleeder resistor used for open-phase input residual voltage discharge and a resistance attenuation network used for attenuating a high-voltage signal. A residual voltage bleeder resistor is connected between each live wire and the null line; a resistance attenuation network is connected between each live wire and the inverted input end of the corresponding differential amplifier, and after the in-phase input ends of the three differential amplifiers are connected together, a resistance attenuation network is also connected between the joint and the zero line. The alternating-current voltage acquisition circuit not only can realize alternating-current voltage acquisition, but also is low in cost, small in size, small in occupied space, convenient to install and high in safety.

Description

Technical Field

[0001] This utility model belongs to the field of AC voltage acquisition technology, specifically relating to a three-phase four-wire AC voltage acquisition circuit. Background Technology

[0002] In molded case circuit breakers (MCCBs), AC voltage acquisition is an indispensable function, providing effective data for identifying faults such as undervoltage and phase loss on the line. Traditional acquisition circuits are generally divided into isolated and non-isolated types. Isolated AC voltage acquisition circuits, as described in Chinese Utility Model Patent No. CN216816781U, mainly use Hall effect sensors or voltage transformers connected to an operational amplifier and an analog-to-digital converter (AD) for acquisition. However, they are costly, and the sensors are generally large, limiting installation options. Non-isolated AC voltage acquisition circuits, as described in Chinese Utility Model Patent No. CN216117780U, use a common ground method between the input N pole and the system GND. However, this non-isolated resistor voltage divider method has the following drawback: connecting the input L and N poles to the system GND poses a safety hazard, increasing the risk of electric shock to the user. Utility Model Content

[0003] To address the aforementioned problems, the purpose of this utility model is to provide a three-phase four-wire AC voltage acquisition circuit that is low in cost, small in size, easy to install, and highly safe.

[0004] The objective of this utility model is achieved through the following technical solution:

[0005] A three-phase four-wire AC voltage acquisition circuit includes a differential amplifier circuit, a high-value resistor network, and a voltage reference circuit. The output terminal of the differential amplifier circuit is connected to an ADC acquisition interface. The differential amplifier circuit includes three differential amplifiers: a first differential amplifier, a second differential amplifier, and a third differential amplifier. The voltage reference circuit is used for neutral line raising. The high-value resistor network includes a residual voltage discharge resistor for discharging residual voltage from a phase-loss input and a resistor attenuation network for attenuating high-voltage signals. A residual voltage discharge resistor is connected between each live wire and the neutral wire. A resistor attenuation network is connected between each live wire and the inverting input terminal of its corresponding differential amplifier. Furthermore, after the non-inverting input terminals of the three differential amplifiers are connected together, a resistor attenuation network is also connected between this connection point and the neutral wire.

[0006] The live wires include phase A, phase B, and phase C, and the neutral wire is the N phase.

[0007] A residual voltage discharge resistor is connected between the AC voltage input LA of phase A and the AC voltage input LN of phase N, between the AC voltage input LB of phase B and the AC voltage input LN of phase N, and between the AC voltage input LC of phase C and the AC voltage input LN of phase N.

[0008] A resistor attenuation network is connected between the AC voltage input LA of phase A and the inverting input of the first differential amplifier, between the AC voltage input LB of phase B and the inverting input of the second differential amplifier, between the AC voltage input LC of phase C and the inverting input of the third differential amplifier, and between the AC voltage input LN of phase N and the non-inverting inputs of the three differential amplifiers.

[0009] The residual voltage discharge resistors include residual voltage discharge resistors R1-R3; the resistor attenuation network includes resistor attenuation networks R4-R7; wherein...

[0010] The residual voltage discharge resistor R1 is connected between the AC voltage input LA of phase A and the AC voltage input LN of phase N; the residual voltage discharge resistor R2 is connected between the AC voltage input LB of phase B and the AC voltage input LN of phase N; the residual voltage discharge resistor R3 is connected between the AC voltage input LC of phase C and the AC voltage input LN of phase N.

[0011] The resistor attenuation network R7 is connected between the AC voltage input LA of phase A and the inverting input of the first differential amplifier; the resistor attenuation network R6 is connected between the AC voltage input LB of phase B and the inverting input of the second differential amplifier; the resistor attenuation network R5 is connected between the AC voltage input LC of phase C and the inverting input of the third differential amplifier; one end of the resistor attenuation network R4 is connected to the AC voltage input LN of phase N, and the other end is connected to the non-inverting inputs of the three differential amplifiers respectively.

[0012] This invention not only enables AC voltage acquisition, but also features low cost, small size, small footprint, easy installation, and high safety. Attached Figure Description

[0013] The structure of this utility model will be further described in detail below with reference to the accompanying drawings.

[0014] Figure 1 This is a circuit block diagram of the three-phase four-wire AC voltage acquisition circuit described in this utility model.

[0015] Figure 2 This is a circuit diagram of the high-value resistor network described in this utility model.

[0016] Figure 3 This is a circuit diagram of the differential amplifier circuit described in this utility model.

[0017] Figure 4 This is a circuit diagram of the voltage reference circuit described in this utility model. Detailed Implementation

[0018] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. The described embodiments are merely some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0019] In the description of this utility model, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" or "linked" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances. It should be noted that the terms "comprising," "including," or any other variations are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Example

[0020] like Figure 1-4 As shown, this embodiment provides a three-phase four-wire AC voltage acquisition circuit, including a differential amplifier circuit, a high-value resistor network, and a voltage reference circuit.

[0021] The high-value resistor network includes a residual voltage discharge resistor for discharging residual voltage from a phase-loss input and a resistor attenuation network for attenuating the high-voltage signal. A residual voltage discharge resistor is connected between each live wire and the neutral wire. A resistor attenuation network is connected between each live wire and the inverting input of its corresponding differential amplifier. Additionally, after the non-inverting inputs of the three differential amplifiers are connected together, a resistor attenuation network is also connected between this connection and the neutral wire. Each residual voltage discharge resistor includes one or more discharge resistors connected in series; each resistor attenuation network includes one or more attenuation resistors connected in series.

[0022] The live wires include phase A, phase B, and phase C, while the neutral wire is the phase N.

[0023] A residual voltage discharge resistor is connected between the AC voltage input LA of phase A and the AC voltage input LN of phase N, between the AC voltage input LB of phase B and the AC voltage input LN of phase N, and between the AC voltage input LC of phase C and the AC voltage input LN of phase N.

[0024] A resistor attenuation network is connected between the AC voltage input LA of phase A and the inverting input of the first differential amplifier, the AC voltage input LB of phase B and the inverting input of the second differential amplifier, the AC voltage input LC of phase C and the inverting input of the third differential amplifier, and the AC voltage input LN of phase N and the non-inverting input of the three differential amplifiers, respectively, to attenuate the high voltage signal.

[0025] Specifically, the residual voltage discharge resistor includes residual voltage discharge resistors R1-R3; the resistor attenuation network includes resistor attenuation networks R4-R7.

[0026] The residual voltage bleeder resistor R1 is connected between the AC voltage input LA of phase A and the AC voltage input LN of phase N. When there is no voltage input to phase A, resistor R1 is used to bleed the residual voltage of phase A to phase N. The residual voltage bleeder resistor R2 is connected between the AC voltage input LB of phase B and the AC voltage input LN of phase N. When there is no voltage input to phase B, resistor R2 is used to bleed the residual voltage of phase B to phase N. The residual voltage bleeder resistor R3 is connected between the AC voltage input LC of phase C and the AC voltage input LN of phase N. When there is no voltage input to phase C, resistor R3 is used to bleed the residual voltage of phase C to phase N.

[0027] The resistor attenuation network R7 is connected between the AC voltage input LA of phase A and the inverting input of the first differential amplifier; the resistor attenuation network R6 is connected between the AC voltage input LB of phase B and the inverting input of the second differential amplifier; the resistor attenuation network R5 is connected between the AC voltage input LC of phase C and the inverting input of the third differential amplifier; one end of the resistor attenuation network R4 is connected to the AC voltage input LN of phase N, and the other end is connected to the non-inverting inputs of the three differential amplifiers respectively.

[0028] The output of the differential amplifier circuit is connected to the ADC acquisition interface. The differential amplifier circuit includes three differential amplifiers, namely the first differential amplifier, the second differential amplifier, and the third differential amplifier.

[0029] The first differential amplifier includes operational amplifier U2A, capacitors C4, C7, and C10, resistors R11 and R14, forming a standard differential amplifier circuit. Resistor R11 serves as the feedback resistor for operational amplifier U2A, used to adjust the attenuation coefficient. Capacitor C4 is used for input filtering, and resistors R14 and capacitor C10 are used for RC filtering of the output of operational amplifier U2A. C7 is an integrating capacitor for waveform smoothing. Operational amplifier U2A is a dual-supply operational amplifier with two input terminals and one output terminal. It also has two additional terminals connected to the system voltage VCC and ground, respectively. One input terminal of operational amplifier U2A is connected to the output terminal S_LA of the resistor attenuation network R7, one end of capacitor C4, one end of capacitor C7, and one end of resistor R11. The other input terminal of operational amplifier U2A is connected to the output terminal S_LN of the resistor attenuation network R4 and the other end of capacitor C4. The output terminals are connected to the other end of capacitor C7, the other end of resistor R11, and one end of resistor R14 respectively; the other end of resistor R14 and one end of capacitor C10 are both connected to the ADC acquisition interface ADC_VA, and the other end of capacitor C10 is grounded.

[0030] The second differential amplifier includes operational amplifier U1A, capacitors C3, C6, and C9, resistors R10 and R13, forming a standard differential amplifier circuit. Resistor R10 serves as the feedback resistor for operational amplifier U1A, used to adjust the attenuation coefficient. Capacitor C3 is used for input filtering, and resistors R13 and capacitor C9 are used for RC filtering of the output of operational amplifier U1A. C6 is an integrating capacitor for waveform smoothing. Operational amplifier U1A is a dual-supply operational amplifier with two input terminals and one output terminal. It also has two additional terminals connected to the system voltage VCC and ground, respectively. One input terminal of operational amplifier U1A is connected to the output terminal S_LB of the resistor attenuation network R6, one end of capacitor C3, one end of capacitor C6, and one end of resistor R10. The other input terminal of operational amplifier U1A is connected to the output terminal S_LN of the resistor attenuation network R4 and the other end of capacitor C3. The output terminals are connected to the other end of capacitor C6, the other end of resistor R10, and one end of resistor R13 respectively; the other end of resistor R13 and one end of capacitor C9 are both connected to the ADC acquisition interface ADC_VB, and the other end of capacitor C9 is grounded.

[0031] The third differential amplifier includes operational amplifier U1B, capacitors C2, C5, and C8, resistors R9 and R12, which together form a standard differential amplifier circuit. Resistor R9 serves as the feedback resistor for operational amplifier U1B, used to adjust the attenuation coefficient. Capacitor C2 is used for input filtering, and resistors R12 and capacitor C8 are used for output RC filtering of operational amplifier U1B. C5 is an integrating capacitor for waveform smoothing. Operational amplifier U1B is a single-supply operational amplifier with two input terminals and one output terminal. One input terminal of operational amplifier U1B is connected to the output terminal S_LC of resistor attenuation network R5, one end of capacitor C2, one end of capacitor C5, and one end of resistor R9. The other input terminal of operational amplifier U1B is connected to the output terminal S_LN of resistor attenuation network R4 and the other end of capacitor C2. The output terminal of operational amplifier U1B is connected to the other end of capacitor C5, the other end of resistor R9, and one end of resistor R12. The other end of resistor R12 and one end of capacitor C8 are both connected to the ADC acquisition interface ADC_VA, and the other end of capacitor C8 is grounded.

[0032] The differential amplifier circuit also includes a resistor R8 and a capacitor C1 connected in parallel, with capacitor C1 used for voltage boosting and filtering. One end of resistor R8 and capacitor C1 is connected to the output terminal VREF of the voltage reference circuit, and the other end of resistor R8 and capacitor C1 is connected to the output terminal S_LN of the resistor attenuation network R4.

[0033] The voltage reference circuit includes operational amplifier U2B, resistors R15 and R16. Operational amplifier U2B is a single-supply operational amplifier with two inputs and one output. One input of operational amplifier U2B is connected to one end of resistor R15 and one end of resistor R16. The other input and output of operational amplifier U2B are connected to the output terminal VREF of the voltage reference circuit. The other end of resistor R15 is grounded. The other end of resistor R16 is connected to the system voltage VCC. The system voltage VCC is divided by resistors R15 and R16 and then used as a voltage reference signal by the voltage follower formed by operational amplifier U2B.

[0034] Phase A, phase B, phase C, and phase N are differentially input to the operational amplifier via a high-value resistor network. The feedback resistor of the operational amplifier is adjusted to obtain a suitable amplification factor, and the output is sent to the ADC acquisition interface.

[0035] Working principle

[0036] The principle of AC voltage acquisition for phase A is as follows: The AC voltage signal is input from the AC voltage input LA of phase A line to the resistor attenuation network R7 (the number of attenuation resistors depends on the resistor package and withstand voltage, and can be one or more). The output terminal S_LA of the resistor attenuation network R7 is connected to the inverting input terminal of the first differential amplifier. At the same time, the AC voltage input LN of phase N line is connected to the non-inverting input terminal of the first differential amplifier through the output terminal S_LN of the resistor attenuation network R4 (the number of attenuation resistors depends on the resistor package and withstand voltage, and can be one or more). The attenuation coefficient can be adjusted by adjusting the feedback resistor R11. The voltage range output to the ADC by the ADC_VA interface is implemented. The voltage reference circuit is used to raise the neutral line (N-phase line). Since a single-supply op-amp (operational amplifier U2B) is used, the acquired waveform is raised to half of the system voltage VCC to ensure the integrity of the voltage waveform. At the same time, the residual voltage discharge resistor R1 (the number of discharge resistors is related to the resistor package and voltage rating, and can be one or more) is connected to the AC voltage input LA of the A-phase line and the AC voltage input LN of the N-phase line. It is used to discharge the residual voltage at the port when the input voltage of the A-phase line is zero, so as to ensure accurate acquisition in the subsequent stage.

[0037] The principle of B-phase AC voltage acquisition is as follows: The AC voltage signal is input from the AC voltage input LB of the B-phase line to the resistor attenuation network R6 (the number of attenuation resistors is related to the resistor package and withstand voltage, and can be one or more). The output terminal S_LB of the resistor attenuation network R6 is connected to the inverting input terminal of the second differential amplifier. At the same time, the AC voltage input LN of the N-phase line is connected to the non-inverting input terminal of the second differential amplifier through the output terminal S_LN of the resistor attenuation network R4 (the number of attenuation resistors is related to the resistor package and withstand voltage, and can be one or more). By adjusting the feedback resistor R10, the attenuation coefficient can be adjusted to realize the voltage range of the ADC acquisition interface ADC_VB output to the ADC. Meanwhile, the residual voltage discharge resistor R2 (the number of discharge resistors is related to the resistor package and withstand voltage, and can be one or more) is connected to the AC voltage input LB of the B-phase line and the AC voltage input LN of the N-phase line. It is used to discharge the residual voltage at the port when the input voltage of the B-phase line is zero, so as to ensure accurate acquisition in the subsequent stage.

[0038] The principle of C-phase AC voltage acquisition is as follows: The AC voltage signal is input from the C-phase line AC voltage input LC to the resistor attenuation network R5 (the number of attenuation resistors is related to the resistor package and withstand voltage, and can be one or more). The output terminal S_LC of the resistor attenuation network R5 is connected to the inverting input terminal of the third differential amplifier. At the same time, the N-phase line AC voltage input LN is connected to the non-inverting input terminal of the third differential amplifier through the output terminal S_LN of the resistor attenuation network R4 (the number of attenuation resistors is related to the resistor package and withstand voltage, and can be one or more). By adjusting the feedback resistor R9, the attenuation coefficient can be adjusted to realize the voltage range of the ADC acquisition interface ADC_VC output to the ADC. Meanwhile, the residual voltage discharge resistor R3 (the number of discharge resistors is related to the resistor package and withstand voltage, and can be one or more) is connected to the C-phase line AC voltage input LC and the N-phase line AC voltage input LN. It is used to discharge the residual voltage at the port when the C-phase line input voltage is zero, so as to ensure accurate acquisition in the subsequent stage.

[0039] Other aspects of this utility model that are not detailed herein are all conventional techniques known to those skilled in the art.

[0040] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0041] The scope of protection of this utility model is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of this utility model shall fall within the scope of protection of this utility model.

Claims

1. A three-phase four-wire AC voltage acquisition circuit, comprising a differential amplifier circuit, a high-value resistor network, and a voltage reference circuit, wherein the output terminal of the differential amplifier circuit is connected to an ADC acquisition interface, and the differential amplifier circuit comprises three differential amplifiers, namely a first differential amplifier, a second differential amplifier, and a third differential amplifier; the voltage reference circuit is used for neutral line raising; characterized in that: The high-value resistor network includes a residual voltage discharge resistor for discharging residual voltage from a phase-loss input and a resistor attenuation network for attenuating high-voltage signals; a residual voltage discharge resistor is connected between each live wire and the neutral wire; a resistor attenuation network is connected between each live wire and the inverting input terminal of its corresponding differential amplifier, and a resistor attenuation network is also connected between the non-inverting input terminals of the three differential amplifiers and the neutral wire at the connection point.

2. The three-phase four-wire AC voltage acquisition circuit according to claim 1, characterized in that: Each residual voltage discharge resistor includes one or more discharge resistors connected in series; each resistor attenuation network includes one or more attenuation resistors connected in series.

3. The three-phase four-wire AC voltage acquisition circuit according to claim 1, characterized in that: The live wires include phase A, phase B, and phase C, and the neutral wire is the N phase. A residual voltage discharge resistor is connected between the AC voltage input LA of phase A and the AC voltage input LN of phase N, between the AC voltage input LB of phase B and the AC voltage input LN of phase N, and between the AC voltage input LC of phase C and the AC voltage input LN of phase N. A resistor attenuation network is connected between the AC voltage input LA of phase A and the inverting input of the first differential amplifier, between the AC voltage input LB of phase B and the inverting input of the second differential amplifier, between the AC voltage input LC of phase C and the inverting input of the third differential amplifier, and between the AC voltage input LN of phase N and the non-inverting inputs of the three differential amplifiers.

4. The three-phase four-wire AC voltage acquisition circuit according to claim 3, characterized in that: The residual voltage discharge resistors include residual voltage discharge resistors R1-R3; the resistor attenuation network includes resistor attenuation networks R4-R7; wherein... The residual voltage discharge resistor R1 is connected between the AC voltage input LA of phase A and the AC voltage input LN of phase N; the residual voltage discharge resistor R2 is connected between the AC voltage input LB of phase B and the AC voltage input LN of phase N; the residual voltage discharge resistor R3 is connected between the AC voltage input LC of phase C and the AC voltage input LN of phase N. The resistor attenuation network R7 is connected between the AC voltage input LA of phase A and the inverting input of the first differential amplifier; the resistor attenuation network R6 is connected between the AC voltage input LB of phase B and the inverting input of the second differential amplifier; the resistor attenuation network R5 is connected between the AC voltage input LC of phase C and the inverting input of the third differential amplifier; one end of the resistor attenuation network R4 is connected to the AC voltage input LN of phase N, and the other end is connected to the non-inverting inputs of the three differential amplifiers respectively.

5. The three-phase four-wire AC voltage acquisition circuit according to claim 4, characterized in that: In the differential amplifier circuit, The first differential amplifier includes operational amplifier U2A, capacitors C4, C7, and C10, resistors R11 and R14. Operational amplifier U2A is a dual-supply operational amplifier with two input terminals and one output terminal. It also has two additional terminals connected to the system voltage VCC and ground, respectively. One input terminal of operational amplifier U2A is connected to the output terminal S_LA of the resistor attenuation network R7, one end of capacitor C4, one end of capacitor C7, and one end of resistor R11. The other input terminal of operational amplifier U2A is connected to the output terminal S_LN of the resistor attenuation network R4 and the other end of capacitor C4. The output terminal of operational amplifier U2A is connected to the other end of capacitor C7, the other end of resistor R11, and one end of resistor R14. The other end of resistor R14 and one end of capacitor C10 are both connected to the ADC acquisition interface ADC_VA. The other end of capacitor C10 is grounded. The second differential amplifier includes operational amplifier U1A, capacitors C3, C6, and C9, resistors R10 and R13. Operational amplifier U1A is a dual-supply operational amplifier with two input terminals and one output terminal. It also has two additional terminals connected to the system voltage VCC and ground, respectively. One input terminal of operational amplifier U1A is connected to the output terminal S_LB of resistor attenuation network R6, one end of capacitor C3, one end of capacitor C6, and one end of resistor R10. The other input terminal of operational amplifier U1A is connected to the output terminal S_LN of resistor attenuation network R4 and the other end of capacitor C3. The output terminal of operational amplifier U1A is connected to the other end of capacitor C6, the other end of resistor R10, and one end of resistor R13. The other end of resistor R13 and one end of capacitor C9 are both connected to the ADC acquisition interface ADC_VB, and the other end of capacitor C9 is grounded. The third differential amplifier includes operational amplifier U1B, capacitors C2, C5, and C8, resistors R9 and R12. Operational amplifier U1B is a single-supply operational amplifier with two input terminals and one output terminal. One input terminal of operational amplifier U1B is connected to the output terminal S_LC of resistor attenuation network R5, one end of capacitor C2, one end of capacitor C5, and one end of resistor R9. The other input terminal of operational amplifier U1B is connected to the output terminal S_LN of resistor attenuation network R4 and the other end of capacitor C2. The output terminal of operational amplifier U1B is connected to the other end of capacitor C5, the other end of resistor R9, and one end of resistor R12. The other end of resistor R12 and one end of capacitor C8 are both connected to the ADC acquisition interface ADC_VA, and the other end of capacitor C8 is grounded.

6. The three-phase four-wire AC voltage acquisition circuit according to claim 5, characterized in that: The differential amplifier circuit also includes a resistor R8 and a capacitor C1 connected in parallel. One end of the resistor R8 and the capacitor C1 is connected to the output terminal VREF of the voltage reference circuit, and the other end of the resistor R8 and the capacitor C1 is connected to the output terminal S_LN of the resistor attenuation network R4.

7. The three-phase four-wire AC voltage acquisition circuit according to claim 6, characterized in that: The voltage reference circuit includes operational amplifier U2B, resistor R15, and resistor R16. Operational amplifier U2B is a single-supply operational amplifier with two input terminals and one output terminal. One input terminal of operational amplifier U2B is connected to one end of resistor R15 and one end of resistor R16. The other input terminal and output terminal of operational amplifier U2B are connected to the output terminal VREF of the voltage reference circuit. The other end of resistor R15 is grounded. The other end of resistor R16 is connected to the system voltage VCC.

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