A three-phase intelligent electric energy meter back-end load detection circuit

Abstract

The utility model discloses a three -phase intelligent electric energy meter back end load detection circuit relates to circuit detection technical field, including first voltage control circuit, second voltage control circuit, third voltage control circuit, load circuit, output voltage detection circuit and main control chip U1, the input of first voltage control circuit, the input of second voltage control circuit and the input of third voltage control circuit are connected A phase voltage, B phase voltage and C phase voltage respectively, and the output of first voltage control circuit, the output of second voltage control circuit, the output of third voltage control circuit all are connected with output voltage electric detection circuit, the main control chip U1 is connected with output voltage detection circuit, output voltage detection circuit includes diode D1, diode D2, diode D3, voltage stabilizing diode D4 and triode Q1, the utility model has the beneficial effects: can judge whether the electric energy meter back end exists load, and excludes the security risk that exists when electric energy meter switch -on.

Description

Technical Field

[0001] This utility model relates to the field of circuit detection technology, and more specifically, to a load detection circuit for the back end of a three-phase smart meter. Background Technology

[0002] During use, electricity meters often experience power outages due to unpaid bills or electricity theft. Once the user has recharged and the theft has been resolved, the meter needs to be switched back on to ensure normal power supply. Switching back on without performing load checks on the meter can easily lead to electric shocks, damage to electrical equipment, and other accidents, posing a significant safety hazard to users.

[0003] Therefore, this utility model provides a load detection circuit for the back end of a three-phase smart meter, which can determine whether there is a load at the back end of the meter and eliminate potential safety hazards when the meter is switched on. Utility Model Content

[0004] In order to overcome the shortcomings of the existing technology, this utility model provides a load detection circuit for the back end of a three-phase smart meter, which can determine whether there is a load at the back end of the meter and eliminate potential safety hazards when the meter is switched on.

[0005] The technical solution adopted by this utility model to solve its technical problem is: a load detection circuit for the back end of a three-phase smart energy meter, the improvement of which is that the load detection circuit for the back end of the three-phase smart energy meter includes a first voltage control circuit, a second voltage control circuit, a third voltage control circuit, a load circuit, an output voltage detection circuit, and a main control chip U1; the input terminals of the first voltage control circuit, the second voltage control circuit, and the third voltage control circuit are respectively connected to the A-phase voltage, the B-phase voltage, and the C-phase voltage, and the output terminals of the first voltage control circuit, the second voltage control circuit, and the third voltage control circuit are all connected to the output voltage detection circuit; the load circuit is respectively connected between the output terminals of the first voltage control circuit, the second voltage control circuit, and the third voltage control circuit and the neutral line; the main control chip U1 is connected to the output voltage detection circuit.

[0006] The output voltage detection circuit includes diodes D1, D2, D3, Zener diode D4, and transistor Q1. The anode of diode D1 is connected to the output terminal of the first voltage control circuit, and its cathode is connected to the cathode of the Zener diode. The anode of diode D2 is connected to the output terminal of the second voltage control circuit, and its cathode is connected to the cathode of the Zener diode D4. The anode of diode D3 is connected to the output terminal of the third voltage control circuit, and its cathode is connected to the cathode of the Zener diode D4. The anode of Zener diode D4 is connected to the neutral line. The base of transistor Q1 is connected to the cathode of Zener diode D4, its collector is connected to the main control chip U1, and its emitter is connected to the neutral line.

[0007] In the above structure, the load circuit includes resistors RL1, RL2, and RL3; resistor RL1 is connected between the output terminal of the first voltage control circuit and the neutral line; resistor RL2 is connected between the output terminal of the second voltage control circuit and the neutral line; and resistor RL3 is connected between the output terminal of the third voltage control circuit and the neutral line.

[0008] In the above structure, the output voltage detection circuit further includes resistors R4, R8, R12, R13, R14, and R15; resistor R4 is connected between the output terminal of the first voltage control circuit and the anode of diode D1; resistor R8 is connected between the output terminal of the second voltage control circuit and the anode of diode D2; resistor R12 is connected between the output terminal of the third voltage control circuit and the anode of diode D3; resistor R13 is connected between the cathode of diode D1 / diode D2 / diode D3 and the cathode of Zener diode D4; one end of resistor R14 is connected to a +5V DC voltage, and the other end is connected to the collector of transistor Q1; one end of resistor R15 is connected to the emitter of transistor Q1, and the other end is connected to the neutral wire.

[0009] In the above structure, the output voltage detection circuit also includes a capacitor C1, which is connected between the collector of transistor Q1 and the neutral line.

[0010] In the above structure, the first voltage control circuit includes resistors R1, R2, and R3, and a relay S1; one end of resistor R1 is connected to one end of relay S1 and is connected to phase A voltage, and the other end of resistor R1 is connected to one end of resistor R2; the other end of resistor R2 is connected to one end of resistor R3; and the other end of resistor R3 is connected to one end of resistor R1, one end of resistor R4, and the other end of relay S1.

[0011] In the above structure, the second voltage control circuit includes resistors R5, R6, and R7, and relay S2; one end of resistor R5 is connected to one end of relay S2 and is connected to phase B voltage, and the other end of resistor R5 is connected to one end of resistor R6; the other end of resistor R6 is connected to one end of resistor R7; the other end of resistor R7 is connected to one end of resistor RL2, one end of resistor R8, and the other end of relay S2.

[0012] In the above structure, the third voltage control circuit includes resistors R9, R10, and R11, and relay S3; one end of resistor R9 is connected to one end of relay S3 and is connected to the C-phase voltage, and the other end of resistor R9 is connected to one end of resistor R10; the other end of resistor R10 is connected to one end of resistor R11; the other end of resistor R11 is connected to one end of resistor R13, one end of resistor R12, and the other end of relay S3.

[0013] The beneficial effects of this utility model are as follows: This utility model converts the load state into a level signal by utilizing the switching characteristics of diodes D1, D2, D3, Zener diode D4, and transistor Q1. The main control chip U1 determines the load condition by observing the waveform of the level signal input through the collector of transistor Q1. Specifically, when no load is connected to the outputs of the first, second, and third voltage control circuits, the waveform of the collector level signal of transistor Q1 is a continuous low level. When only one phase of the outputs of the first, second, and third voltage control circuits is connected to a load, the waveform of the collector level signal of transistor Q1 is a rectangular wave. When two phases of the outputs of the first, second, and third voltage control circuits are connected to a load, the waveform of the collector level signal of transistor Q1 is a square wave. When all three outputs of the first, second, and third voltage control circuits are connected to a load, the waveform of the collector level signal of transistor Q1 is a continuous high level. Therefore, this utility model can determine whether there is a load at the back end of the electricity meter and eliminate potential safety hazards when the electricity meter is switched on. Attached Figure Description

[0014] Figure 1 This is a block diagram of a back-end load detection circuit for a three-phase smart meter according to the present invention.

[0015] Figure 2 This is a circuit diagram of a back-end load detection circuit for a three-phase smart meter according to the present invention.

[0016] Figure 3 This invention relates to a detection waveform of a load detection circuit at the back end of a three-phase smart meter. Figure 1 ;

[0017] Figure 4 This invention relates to a detection waveform of a load detection circuit at the back end of a three-phase smart meter. Figure 2 ;

[0018] Figure 5 This invention relates to a detection waveform of a load detection circuit at the back end of a three-phase smart meter. Figure 3 ;

[0019] Figure 6 This invention relates to a detection waveform of a load detection circuit at the back end of a three-phase smart meter. Figure 4 . Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] The following will clearly and completely describe the concept, specific structure, and technical effects of this utility model in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are all within the scope of protection of this utility model. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this utility model can be combined interactively without contradicting each other.

[0022] Reference Figure 1 As shown, this utility model discloses a load detection circuit for a three-phase smart energy meter. The load detection circuit includes a first voltage control circuit 1, a second voltage control circuit 2, a third voltage control circuit 3, a load circuit 4, an output voltage detection circuit 5, and a main control chip U1. The input terminals of the first voltage control circuit 1, the second voltage control circuit 2, and the third voltage control circuit 3 are respectively connected to phase A voltage, phase B voltage, and phase C voltage. The output terminals of the first voltage control circuit 1, the second voltage control circuit 2, and the third voltage control circuit 3 are all connected to the output voltage detection circuit. The load circuit 4 is connected between the output terminals of the first voltage control circuit 1, the second voltage control circuit 2, and the third voltage control circuit 3 and the neutral line. The main control chip U1 is connected to the output voltage detection circuit 5.

[0023] In this embodiment, refer to Figure 2As shown, the output voltage detection circuit 5 includes diodes D1, D2, D3, Zener diode D4, transistor Q1, resistors R4, R8, R12, R13, R14, and R15, and capacitor C1. The anode of diode D1 is connected to the output terminal of the first voltage control circuit 1, and its cathode is connected to the cathode of the Zener diode. The anode of diode D2 is connected to the output terminal of the second voltage control circuit 2, and its cathode is connected to the cathode of the Zener diode D4. The anode of diode D3 is connected to the output terminal of the third voltage control circuit 3, and its cathode is connected to the cathode of the Zener diode D4. The anode of the Zener diode D4 is connected to the neutral wire. The base of transistor Q1 is connected to the cathode of Zener diode D4, and its collector is connected to... The main control chip U1 is connected, with its emitter connected to the neutral line; resistor R4 is connected between the output of the first voltage control circuit 1 and the anode of diode D1; resistor R8 is connected between the output of the second voltage control circuit 2 and the anode of diode D2; resistor R12 is connected between the output of the third voltage control circuit 3 and the anode of diode D3; resistor R13 is connected between the cathode of diode D1 / diode D2 / diode D3 and the cathode of Zener diode D4; one end of resistor R14 is connected to a +5V DC voltage, and the other end is connected to the collector of transistor Q1; one end of resistor R15 is connected to the emitter of transistor Q1, and the other end is connected to the neutral line; capacitor C1 is connected between the collector of transistor Q1 and the neutral line.

[0024] Furthermore, referring to Figure 2 As shown, the load circuit 4 includes resistors RL1, RL2, and RL3; resistor RL1 is connected between the output terminal of the first voltage control circuit 1 and the neutral line; resistor RL2 is connected between the output terminal of the second voltage control circuit 2 and the neutral line; and resistor RL3 is connected between the output terminal of the third voltage control circuit 3 and the neutral line.

[0025] Continue to refer to Figure 2As shown, the first voltage control circuit 1 includes resistors R1, R2, R3, and relay S1; one end of resistor R1 is connected to one end of relay S1 and is connected to phase A voltage, and the other end of resistor R1 is connected to one end of resistor R2; the other end of resistor R2 is connected to one end of resistor R3; the other end of resistor R3 is connected to one end of resistor RL1, the anode of diode D1, and the other end of relay S1; the second voltage control circuit 2 includes resistors R5, R6, R7, and relay S2; one end of resistor R5 is connected to one end of relay S2 and is connected to phase B voltage, and the other end of resistor R5 is connected to... One end of R6 is connected; the other end of resistor R6 is connected to one end of resistor R7; the other end of resistor R7 is connected to one end of resistor RL2, the anode of diode D2, and the other end of relay S2; the third voltage control circuit 3 includes resistors R9, R10, R11, and relay S3; one end of resistor R9 is connected to one end of relay S3 and is connected to phase C voltage, and the other end of resistor R9 is connected to one end of resistor R10; the other end of resistor R10 is connected to one end of resistor R11; the other end of resistor R11 is connected to one end of resistor RL3, the anode of diode D3, and the other end of relay S3.

[0026] Based on the circuit structure described above, the specific working principle of this embodiment is as follows:

[0027] During normal power supply, relays S1, S2, and S3 are all in the closed state. At this time, resistors R1-R3, R5-R7, and R9-R11 are short-circuited with relays S1, S2, and S3 respectively. The user-end load (resistors RL1, RL2, and RL3) are connected between A-OUT (output of the first voltage control circuit 1), B-OUT (output of the second voltage control circuit 2), C-OUT (output of the third voltage control circuit 3), and the neutral line respectively. At this time, the load detection circuit does not perform load detection.

[0028] When the circuit is tripped, relays S1, S2 and S3 trip (disconnect) simultaneously. At this time, resistors R1-R3 are connected to phase A voltage, resistors R5-R7 are connected to phase B voltage, and resistors R9-R11 are connected to phase C voltage. The angle between the three phase voltages of phase A, phase B and phase C is 120°.

[0029] When A-OUT, B-OUT, and C-OUT are all unloaded, the AC current of phase A flows through resistors R1-R4 to diode D1, the AC current of phase B flows through resistors R5-R8 to diode D2, and the AC current of phase C flows through resistors R9-R12 to diode D3. This is based on the single-phase conduction of diodes and the principle of calculating the combined phase voltage of three-phase electricity.

[0030] U 合 =U a +U b +U c =V×sin(α+60°); α∈(0°, 60°);

[0031] Within this range, the voltage at the left end of resistor R13 remains positive, the base voltage of transistor Q1 is greater than the emitter voltage, and the transistor is saturated and conducting. Figure 3 As shown, the load detection point level is low at this time;

[0032] When only one of A-OUT, B-OUT, and C-OUT is connected to a load, the following calculation principle applies based on the single-phase conduction of diodes and the combined phase voltage of three-phase electricity:

[0033] U 合 =U a +U b +U c =V×sin(α+60°); α∈(0°, 60°);

[0034] U 合 =U a +U b +U c =V×sinα; α∈(60°, 180°);

[0035] U 合 =0; α∈(180°, 240°);

[0036] U 合 =U a +U b +U c =V×sin(α+120°); α∈(240°, 360°);

[0037] Within this range, the resistance on both sides of resistor R13 is at a low level when α∈(180°, 240°), at which time transistor Q1 is not conducting, and the load detection point is at a high level. In other ranges, transistor Q1 conducts. Figure 4 As shown, the detection level is low at this time. Therefore, in this case, the load detection point level is a rectangular wave with high and low levels.

[0038] When two of A-OUT, B-OUT, and C-OUT are connected to a load, the following calculation principle applies based on the single-phase conduction of diodes and the combined phase voltage of three-phase electricity:

[0039] U 合 =U a +U b +U c =V×sinα; α∈(0°, 180°);

[0040] U 合 =0; α∈(180°, 360°);

[0041] Within this range, the resistance on both sides of resistor R13 is at a low level when α∈(180°, 360°), at which time transistor Q1 is not conducting, and the load detection point is at a high level. In other ranges, transistor Q1 conducts. Figure 5 As shown, the detection level is low at this time. Therefore, in this case, the load detection point level is a square wave with both high and low levels.

[0042] When A-OUT, B-OUT, and C-OUT are all connected to a load, the following calculation principle applies based on the single-phase conduction of diodes and the combined phase voltage of three-phase electricity:

[0043] U 合 =0;

[0044] At this time, transistor Q1 is not conducting, refer to Figure 6 As shown, the test level at the load detection point is high.

[0045] In the above calculation formula, U 合 U represents the combined phase voltage after three-phase voltage rectification; a U represents the instantaneous voltage of phase A. b U represents the instantaneous voltage of phase B. c Represents the instantaneous voltage of phase C; V represents the peak value of the combined phase voltage; α represents the sub-interval variable of the phase angle;

[0046] In summary, if the load detection point continuously detects a low level, it indicates that there is no load at the back end; otherwise, it indicates that there is a load at the back end.

[0047] When the output voltage detection circuit 5 inputs the voltage signal to the main control chip U1, the main control chip can determine whether the back end is connected to a load based on the waveform detected at the back end, and prompt the operator through audible and visual signals to eliminate the safety hazards that exist when the electricity meter is closed; therefore, this embodiment can determine whether there is a load at the back end of the electricity meter and eliminate the safety hazards that exist when the electricity meter is closed.

[0048] The above is a detailed description of the preferred embodiments of the present utility model. However, the present utility model is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present utility model. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A load detection circuit for the back end of a three-phase smart energy meter, characterized in that, The three-phase smart energy meter's back-end load detection circuit includes a first voltage control circuit, a second voltage control circuit, a third voltage control circuit, a load circuit, an output voltage detection circuit, and a main control chip U1. The input terminals of the first, second, and third voltage control circuits are respectively connected to phase A, phase B, and phase C voltages. The output terminals of the first, second, and third voltage control circuits are all connected to the output voltage detection circuit. The load circuit is connected between the output terminals of the first, second, and third voltage control circuits and the neutral wire. The main control chip U1 is connected to the output voltage detection circuit. The output voltage detection circuit includes diodes D1, D2, D3, Zener diode D4, and transistor Q1. The anode of diode D1 is connected to the output terminal of the first voltage control circuit, and its cathode is connected to the cathode of the Zener diode. The anode of diode D2 is connected to the output terminal of the second voltage control circuit, and its cathode is connected to the cathode of the Zener diode D4. The anode of diode D3 is connected to the output terminal of the third voltage control circuit, and its cathode is connected to the cathode of the Zener diode D4. The anode of Zener diode D4 is connected to the neutral line. The base of transistor Q1 is connected to the cathode of Zener diode D4, its collector is connected to the main control chip U1, and its emitter is connected to the neutral line.

2. The three-phase smart energy meter back-end load detection circuit according to claim 1, characterized in that, The load circuit includes resistors RL1, RL2, and RL3; resistor RL1 is connected between the output terminal of the first voltage control circuit and the neutral line; resistor RL2 is connected between the output terminal of the second voltage control circuit and the neutral line; and resistor RL3 is connected between the output terminal of the third voltage control circuit and the neutral line.

3. The three-phase smart energy meter back-end load detection circuit according to claim 2, characterized in that, The output voltage detection circuit further includes resistors R4, R8, R12, R13, R14, and R15. Resistor R4 is connected between the output terminal of the first voltage control circuit and the anode of diode D1. Resistor R8 is connected between the output terminal of the second voltage control circuit and the anode of diode D2. Resistor R12 is connected between the output terminal of the third voltage control circuit and the anode of diode D3. Resistor R13 is connected between the cathode of diode D1 / diode D2 / diode D3 and the cathode of Zener diode D4. One end of resistor R14 is connected to a +5V DC voltage, and the other end is connected to the collector of transistor Q1. One end of resistor R15 is connected to the emitter of transistor Q1, and the other end is connected to the neutral wire.

4. The back-end load detection circuit of a three-phase smart energy meter according to claim 3, characterized in that, The output voltage detection circuit also includes a capacitor C1, which is connected between the collector of transistor Q1 and the neutral line.

5. The back-end load detection circuit of a three-phase smart energy meter according to claim 3, characterized in that, The first voltage control circuit includes resistors R1, R2, and R3, and a relay S1; one end of resistor R1 is connected to one end of relay S1 and is connected to phase A voltage, and the other end of resistor R1 is connected to one end of resistor R2; the other end of resistor R2 is connected to one end of resistor R3; and the other end of resistor R3 is connected to one end of resistor R1, one end of resistor R4, and the other end of relay S1.

6. The back-end load detection circuit of a three-phase smart energy meter according to claim 3, characterized in that, The second voltage control circuit includes resistors R5, R6, and R7, and relay S2; one end of resistor R5 is connected to one end of relay S2 and is connected to phase B voltage, and the other end of resistor R5 is connected to one end of resistor R6; the other end of resistor R6 is connected to one end of resistor R7; the other end of resistor R7 is connected to one end of resistor RL2, one end of resistor R8, and the other end of relay S2.

7. The load detection circuit for a three-phase smart energy meter according to claim 3, characterized in that, The third voltage control circuit includes resistors R9, R10, and R11, and relay S3; one end of resistor R9 is connected to one end of relay S3 and is connected to the C-phase voltage, and the other end of resistor R9 is connected to one end of resistor R10; the other end of resistor R10 is connected to one end of resistor R11; the other end of resistor R11 is connected to one end of resistor R13, one end of resistor R12, and the other end of relay S3.

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