CN104950151A - Device for automatically switching three-wire and four-wire metering modes of three-phase electric energy meter - Google Patents
Device for automatically switching three-wire and four-wire metering modes of three-phase electric energy meter Download PDFInfo
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Abstract
The invention discloses a device for automatically switching three-wire and four-wire metering modes of a three-phase electric energy meter. The device comprises a current sampling circuit and a signal conditioning circuit, wherein the current sampling circuit is used for acquiring a current signal on a zero line UN of a three-phase power supply, and an output end of the current sampling circuit is connected with an input end of the signal conditioning circuit; the signal conditioning circuit is used for converting the current signal into a voltage signal and amplifying, filtering and shaping the voltage signal, and an output end of the signal conditioning circuit is connected with a metering mode switching pin of a metering chip arranged in the three-phase electric energy meter. The device judges the power grid access mode according to the fact that whether current passes through the zero line UN of the three-phase power supply or not, controls the metering modes of the electric energy meter with the simple circuits, improves the metering accuracy and avoids the effect of voltage interference on metering, so that the electric energy meter can perform judgment and mode switching without software, and the circuits are simple in structure, short in delay time, more accurate in metering, economical and practical.
Description
Technical field
The present invention relates to three-phase electric energy meter field, particularly relate to a kind of three-phase electric energy meter three line and four line metering method automatic switching control equipments.
Background technology
Metering method due to threephase AC electric energy is divided into phase three-wire three, three-phase and four-line 2 kinds, therefore three-phase electric energy meter in the past is also divided into three-phase three-wire electric energy meter, three-phase and four-line electric energy meter two class, the metering method, the electric pressure mode of connection etc. of the electric energy meter of this two type are all different, also and incompatible, must buy respectively and install in use procedure, very inconvenient.
And domestic existing self-adaptation three-phase electric energy meter, be all the method for magnitude of voltage or the voltage angle accessed by software interpretation substantially, switch different metering methods.As name is called the access way mainly through the three-phase voltage between phases angle of differentiation access and the scope determination three-phase electric energy meter of three-phase voltage value in the disclosed technical scheme of the Chinese invention patent (Authorization Notice No.: CN102680779A) of " a kind of self-adaptation control method of three-phase electric energy meter and three-phase electric energy meter ", call corresponding handling procedure and quantitative model according to the access way of three-phase electric energy meter.The self-adaptation electric energy meter scheme that this magnitude of voltage according to certain limit and voltage angle carry out the judgement of metering method faces a very large problem now: when voltage ripple of power network, network load change, the result of determination of software can by impact to a certain extent, and this fluctuation situation will cause electric energy meter to measure or erroneous metrology.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art, a kind of three-phase electric energy meter three line and four line metering method automatic switching control equipments are provided, solve prior art and depend on software carries out metering method judgement scheme drawback according to the magnitude of voltage of certain limit and voltage angle, the situation such as voltage fluctuation, load change that reduces measures the impact caused on electric energy meter.
The object of the invention is to be achieved through the following technical solutions: a kind of three-phase electric energy meter three line and four line metering method automatic switching control equipments, comprise current sampling circuit and signal conditioning circuit; The current signal of current sampling circuit on the zero line UN gathering three-phase supply, the output terminal of current sampling circuit is connected with the input end of signal conditioning circuit; Signal conditioning circuit is used for current signal to be converted to voltage signal, and this voltage signal is amplified, filtering and integer process, the output terminal of signal conditioning circuit switches pin with the metering method of the computation chip being arranged at three-phase electric energy meter inside and is connected.
Described current sampling circuit comprises current transformer T, and current transformer T is for gathering the current signal of the zero line UN of three-phase supply, and one end of current transformer T is connected with the input end of signal conditioning circuit, its other end with dock.
Further, described current transformer T is punching current transformer.
Described signal conditioning circuit comprises voltage sampling resistor R1 and amplifier A, one end of voltage sampling resistor R1 is all connected with the output terminal of current sampling circuit with the in-phase input end of amplifier, the other end of voltage sampling resistor R1 and the inverting input of amplifier A all with dock, the output terminal of amplifier A and the metering method of computation chip switch pin and are connected.
Further, described computation chip comprises ATT7022E chip.
The present invention also comprises phase inverter, and the input end of described phase inverter is connected with the output terminal of signal conditioning circuit, and the output terminal of phase inverter switches pin with the metering method of described computation chip and is connected.
The invention has the beneficial effects as follows: whether have electric current by judging the mode of the electrical network accessed according to the zero line UN of three-phase supply, and adopt simple circuit to reach the metering method object controlling electric energy meter, abandon and old judge metering method according to the scope of magnitude of voltage and voltage angle, improve the accuracy of metering, effectively avoid the impact that the fluctuation of line voltage and the change of network load are measured electric energy meter, enable electric energy meter not rely on software and carry out judgement and pattern switching, it is simple that circuit of the present invention has structure, time delay is few, measure more accurate and economical and practical etc. feature.
Accompanying drawing explanation
Fig. 1 is the circuit block diagram of three-phase electric energy meter three line of the present invention and four line metering method automatic switching control equipments;
Fig. 2 is the circuit diagram of three-phase electric energy meter three line of the present invention and four line metering method automatic switching control equipments;
Fig. 3 is the pin configuration figure of ATT7022E chip in the present invention.
Embodiment
Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail, but protection scope of the present invention is not limited to the following stated.
As shown in Figure 1, a kind of three-phase electric energy meter three line and four line metering method automatic switching control equipments, comprise current sampling circuit and signal conditioning circuit; The current signal of current sampling circuit on the zero line UN gathering three-phase supply, the output terminal of current sampling circuit is connected with the input end of signal conditioning circuit; Signal conditioning circuit is used for current signal to be converted to voltage signal, and this voltage signal is amplified, filtering and integer process, the output terminal of signal conditioning circuit switches pin with the metering method of the computation chip being arranged at three-phase electric energy meter inside and is connected.
The three-phase mains voltage end of three-phase electric energy meter accesses Ua, Ub, Uc and UN respectively, phase three-wire three and the difference of three-phase and four-line on zero line (zero line UN) is utilized in this device, namely phase three-wire three does not have zero line, just neutral line current is not had yet, and three line four lines must have zero line, also just neutral line current must be had, be whether zero judge that the electric network source accessed is three-wire system or four-wire system by detecting neutral line current, and controlled the metering method of gauging table by circuit by judged result, to realize the automatic switchover of three-phase electric energy meter three line and four line metering methods.
As shown in Figure 2, described current sampling circuit comprises current transformer T, and current transformer T is for gathering the current signal of the zero line UN of three-phase supply, and one end of current transformer T is connected with the input end of signal conditioning circuit, its other end with dock.
Further, described current transformer T is punching current transformer.
Described signal conditioning circuit comprises voltage sampling resistor R1 and amplifier A, one end of voltage sampling resistor R1 is all connected with the output terminal of current sampling circuit with the in-phase input end of amplifier, the other end of voltage sampling resistor R1 and the inverting input of amplifier A all with dock, the output terminal of amplifier A and the metering method of computation chip switch pin and are connected.
Further, described computation chip comprises ATT7022E chip, and as shown in Figure 3, when the metering method of computation chip switches pin SEL access high level, this computation chip measures with three-phase and four-line metering method; When the metering method switching pin SEL of computation chip connects low level, this computation chip measures with phase three-wire three metering method.
The present invention also comprises phase inverter, and the input end of described phase inverter is connected with the output terminal of signal conditioning circuit, and the output terminal of phase inverter switches pin with the metering method of described computation chip and is connected.
[embodiment 1]
Described computation chip adopts ATT7022E chip, and when the metering method of computation chip switches pin SEL access high level, this computation chip measures with three-phase and four-line metering method; When the metering method switching pin SEL of computation chip connects low level, this computation chip measures with phase three-wire three metering method.
When having electric current to flow through on the zero line UN of three-phase supply, namely three-phase electric energy meter should adopt three-phase and four-line metering method, punching current transformer T in current sampling circuit produces induction current, this sensor current signal changes into voltage signal through voltage sampling resistor R1, amplifier A amplifies this voltage signal again, after filtering and integer process, voltage signal is sent to the SEL pin of ATT7022E computation chip, then ATT7022E model computation chip will adopt three-phase and four-line metering method to measure automatically.
If the zero line UN of three-phase supply does not have electric current to pass through, namely three-phase electric energy meter should adopt phase three-wire three metering method, it is 0 that punching current transformer T in current sampling circuit produces induction current, the voltage signal exported after signal conditioning circuit is low level, and ATT7022E computation chip will adopt phase three-wire three metering method to measure automatically.Realize three lines and the four line metering method automatic switching functions of three-phase electric energy meter thus.
[embodiment 2] is if the model metering method that the computation chip of three-phase electric energy meter inside adopts is: when the metering method of computation chip switches pin access low level, be three-phase and four-line metering method; When the metering method switching pin of computation chip connects high level, be phase three-wire three metering method, then introduce inverter circuit in circuit.
This device also comprise for by phase inverter reverse for current potential, can adopt schmitt inverter, the input end of described phase inverter is connected with the output terminal of signal conditioning circuit, and the output terminal of phase inverter switches pin with the metering method of described computation chip and is connected.
When having electric current to flow through on the zero line UN of three-phase supply, namely three-phase electric energy meter should adopt three-phase and four-line metering method, punching current transformer T in current sampling circuit produces induction current, this sensor current signal changes into voltage signal through voltage sampling resistor R1, amplifier A amplifies this voltage signal again, after filtering and integer process, voltage signal is sent to reverser B, this high level voltage signal is converted to low level voltage signal by reverser B, and send to the SEL pin of ATT7022E computation chip, then ATT7022E model computation chip will adopt three-phase and four-line metering method to measure automatically.
If the zero line UN of three-phase supply does not have electric current to pass through, namely three-phase electric energy meter should adopt phase three-wire three metering method, it is 0 that punching current transformer T in current sampling circuit produces induction current, the voltage signal exported after signal conditioning circuit is low level, output high level voltage signal after reverser B is reverse, ATT7022E computation chip will adopt phase three-wire three metering method to measure automatically.Realize three lines and the four line metering method automatic switching functions of three-phase electric energy meter thus.
The above is only the preferred embodiment of the present invention, be to be understood that the present invention is not limited to the form disclosed by this paper, should not regard the eliminating to other embodiments as, and can be used for other combinations various, amendment and environment, and can in contemplated scope described herein, changed by the technology of above-mentioned instruction or association area or knowledge.And the change that those skilled in the art carry out and change do not depart from the spirit and scope of the present invention, then all should in the protection domain of claims of the present invention.
Claims (6)
1. three-phase electric energy meter three line and four line metering method automatic switching control equipments, is characterized in that: comprise current sampling circuit and signal conditioning circuit; The current signal of current sampling circuit on the zero line UN gathering three-phase supply, the output terminal of current sampling circuit is connected with the input end of signal conditioning circuit; Signal conditioning circuit is used for current signal to be converted to voltage signal, and this voltage signal is amplified, filtering and integer process, the output terminal of signal conditioning circuit switches pin with the metering method of the computation chip being arranged at three-phase electric energy meter inside and is connected.
2. a kind of three-phase electric energy meter three line according to claim 1 and four line metering method automatic switching control equipments, it is characterized in that: described current sampling circuit comprises current transformer T, current transformer T is for gathering the current signal of the zero line UN of three-phase supply, one end of current transformer T is connected with the input end of signal conditioning circuit, its other end with dock.
3. a kind of three-phase electric energy meter three line according to claim 1 and four line metering method automatic switching control equipments, is characterized in that: described current transformer T is punching current transformer.
4. a kind of three-phase electric energy meter three line according to claim 1 and four line metering method automatic switching control equipments, it is characterized in that: described signal conditioning circuit comprises voltage sampling resistor R1 and amplifier A, one end of voltage sampling resistor R1 is all connected with the output terminal of current sampling circuit with the in-phase input end of amplifier, the other end of voltage sampling resistor R1 and the inverting input of amplifier A all with dock, the output terminal of amplifier A and the metering method of computation chip switch pin and are connected.
5. a kind of three-phase electric energy meter three line according to claim 1 and four line metering method automatic switching control equipments, is characterized in that: described computation chip comprises ATT7022E chip.
6. a kind of three-phase electric energy meter three line according to claim 1 and four line metering method automatic switching control equipments, it is characterized in that: also comprise phase inverter, the input end of described phase inverter is connected with the output terminal of signal conditioning circuit, and the output terminal of phase inverter switches pin with the metering method of described computation chip and is connected.
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Cited By (2)
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CN107807345A (en) * | 2017-11-13 | 2018-03-16 | 国家电网公司 | A kind of Three Phase Alternating-current Electrical Energy Meters verification system and method |
CN117192189A (en) * | 2023-11-03 | 2023-12-08 | 浙江正泰物联技术有限公司 | Three-phase voltage measurement circuit, method and three-phase ammeter |
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CN107807345A (en) * | 2017-11-13 | 2018-03-16 | 国家电网公司 | A kind of Three Phase Alternating-current Electrical Energy Meters verification system and method |
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