CN215910552U - High-precision electric power monitor - Google Patents
High-precision electric power monitor Download PDFInfo
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- CN215910552U CN215910552U CN202121662321.XU CN202121662321U CN215910552U CN 215910552 U CN215910552 U CN 215910552U CN 202121662321 U CN202121662321 U CN 202121662321U CN 215910552 U CN215910552 U CN 215910552U
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Abstract
The utility model provides a high-precision electric power monitor, which comprises a CPU, an alternating current signal acquisition unit, a storage unit, an analog quantity transmission output unit and a display unit, wherein the alternating current signal acquisition unit, the storage unit, the analog quantity transmission output unit and the display unit are connected with ports of the CPU; the analog quantity transmission output unit comprises a magnetic isolator, a resistance-capacitance filter circuit, a voltage-current conversion circuit and a current amplification circuit which are sequentially connected from an input end to an output end, wherein the magnetic isolator receives a PWM signal output by a CPU and outputs the isolated PWM signal, and the magnetic isolator also outputs an isolated grounding signal TGND which is used as a common grounding signal of the resistance-capacitance filter circuit, the voltage-current conversion circuit and the current amplification circuit. The common optical coupling isolation is abandoned in the circuit design of the analog quantity transmission output, a magnetic isolation mode is adopted, the magnetic isolation has higher response speed and smaller signal delay compared with the optical coupling isolation, and the circuit adopting the magnetic isolation mode has better linearity and smaller error.
Description
Technical Field
The utility model relates to the technical field of electric power instruments, in particular to a high-precision electric power monitor.
Background
The power monitoring instrument is an instrument for monitoring parameters of a power system, and is used for collecting three-phase alternating-current voltage and current signals and displaying phase voltage, line voltage, phase current, zero-sequence current, leakage current, three-phase active power, total active power, three-phase reactive power, total reactive power, three-phase apparent power, total apparent power, three-phase power factors, total power factors, voltage frequency and the like on the instrument.
The prior art also has the following technical defects:
the power monitoring instrument is generally equipped with a transmitting and outputting function, that is, an acquired alternating current signal (generally, a signal of a voltage transformer or a current transformer) is transmitted to a standard signal of 4-20mA for outputting. In the design of a transmission output circuit, optical coupling isolation is generally adopted for design, and the optical coupling isolation design has certain errors in the actual output of 4-20mA analog quantity, so that the output precision of a power monitor is influenced.
Disclosure of Invention
In order to solve the technical problems in the background art, the utility model provides a high-precision electric power monitor, which abandons the common optical coupling isolation in the circuit design of analog quantity transmission output, adopts a magnetic isolation mode, has faster response speed and smaller signal delay compared with the optical coupling isolation, and has better linearity and smaller error in the circuit adopting the magnetic isolation mode.
In order to achieve the purpose, the utility model adopts the following technical scheme:
a high-precision electric power monitor comprises a CPU, an alternating current signal acquisition unit, a storage unit, an analog quantity transmission output unit and a display unit which are connected with ports of the CPU, and a power supply unit; the device is used for acquiring three-phase alternating voltage and current signals, displaying, transmitting and outputting the signals.
The utility model is characterized in that: the analog quantity transmission output unit comprises a magnetic isolator, a resistance-capacitance filter circuit, a voltage-current conversion circuit and a current amplification circuit which are sequentially connected from an input end to an output end, wherein the magnetic isolator receives a PWM signal output by a CPU and outputs the isolated PWM signal, and simultaneously, the magnetic isolator also outputs an isolated grounding signal TGND which is used as a common grounding signal of the resistance-capacitance filter circuit, the voltage-current conversion circuit and the current amplification circuit.
Further, the magnetic isolator is ADuM 1200.
Further, the power supply unit comprises an AC-DC power supply module and a DC-DC power supply module which are sequentially connected from an input end to an output end, the input end of the AC-DC power supply module is connected with an AC220V power supply, the output end of the AC-DC power supply module outputs a DC12V power supply, meanwhile, the DC12V power supply is also connected with the DC-DC power supply module, the DC-DC power supply module outputs a DC5V power supply again, and the DC12V power supply and the DC5V power supply provide power supplies for the CPU and other units.
Compared with the prior art, the utility model has the beneficial effects that:
(1) the analog quantity transmission output unit abandons the common optical coupling isolation, adopts a magnetic isolation mode, has higher response speed and smaller signal delay compared with the optical coupling isolation, and can be seen in the analog quantity isolation output test that a circuit adopting the magnetic isolation mode has better linearity and smaller error;
(2) the power supply unit of the utility model abandons the conventional design of adopting a multi-output switch power supply as a system power supply, and adopts the design scheme of adopting the combination of an AC-DC module and a DC-DC module as the system power supply, the scheme has the advantages of higher integration level, better modularization, convenient maintenance and the like, and the number of devices used in the new power supply design scheme is greatly reduced compared with that of the conventional switch power supply scheme, the volume is smaller, and the failure rate is lower.
Drawings
FIG. 1 is a block diagram of the overall structure of a high-precision power monitor according to the present invention;
FIG. 2 is a block diagram showing a circuit configuration of an analog quantity transmission output unit according to the present invention;
FIG. 3 is a circuit diagram of a magnetic isolator for the analog variable transmission output unit of the present invention;
FIG. 4 is a diagram of a RC filter circuit, a voltage-to-current converter circuit and a current amplifier circuit of the analog variable transmission output unit according to the present invention;
FIG. 5 is an AC-DC power module circuit diagram of the power supply unit of the present invention;
fig. 6 is a circuit diagram of a DC-DC power supply module of the power supply unit of the present invention.
In the figure: 1-magnetic isolator 2-resistance-capacitance filter circuit 3-voltage-current conversion circuit 4-current amplification circuit 5-amplitude limiting circuit.
Detailed Description
The following detailed description of the present invention will be made with reference to the accompanying drawings.
As shown in fig. 1, the high-precision power monitor comprises a CPU, an ac signal acquisition unit, a storage unit, an analog quantity transmission output unit, a display unit and a power supply unit, wherein the ac signal acquisition unit, the storage unit, the analog quantity transmission output unit and the display unit are connected with ports of the CPU; the device is used for acquiring three-phase alternating voltage and current signals, displaying, transmitting and outputting the signals. The device also comprises a switching value input unit for acquiring switching values (such as equipment failure points) and a communication unit (RS485) for communicating and connecting with external equipment, and the switching value input unit is a part in the prior art.
As shown in fig. 2 to 4, one of the improvement points of the present invention is an analog quantity transmission output unit, which includes a magnetic isolator 1, a resistance-capacitance filter circuit 2, a voltage-current conversion circuit 3 and a current amplification circuit 4 connected in sequence from an input end to an output end.
As shown in fig. 3-4, the magnetic isolator 1 is an ADuM 1200. The magnetic isolator 1 receives a PWM signal (PWM) output by the CPU, outputs an isolated PWM signal (APWM), and the magnetic isolator 1 also outputs an isolated ground signal TGND, which is used as a common ground signal for the rc filter circuit 2, the voltage-to-current converter circuit 3, and the current amplifier circuit 4.
As shown in fig. 4, the input terminal of the rc filter circuit 2 is connected to the isolated PWM signal APWM of the magnetic isolator 1 in fig. 2, and is composed of resistors R8, R9, and R10 connected in series and capacitors C2, C3, and C4 at the lower end thereof, for converting the PWM signal APWM into a voltage signal. The voltage-current conversion circuit 3 is composed of operational amplifiers U12A and UA2B which are connected in sequence and peripheral circuits thereof, a triode Q2 for signal amplification is also connected between the two operational amplifiers, and the voltage-current conversion circuit 3 is used for converting a voltage signal into a current signal. The current amplifying circuit 4 is composed of a triode Q1 and used for amplifying a current signal, an amplified signal output end is AO, a 4-20mA transmission output signal is formed between AO and a grounding signal end TGND, and a capacitor C1 is used for resisting interference. In addition, the amplitude limiting circuit 5 consisting of the diodes D3 and D4 and the capacitors C7 and C8 is used for the input amplitude limitation of the two-stage operational amplifier.
As shown in the following table: in the analog quantity isolation output test, the circuit adopting the magnetic isolation mode has better linearity and smaller error.
As shown in fig. 5-6, a second improvement point of the present invention is a power supply unit, which includes an AC-DC power module U1 and a DC-DC power module U2 connected in sequence from an input end to an output end, the input end of the AC-DC power module U1 is connected to an AC220V power supply, the output end outputs a DC12V power supply, and at the same time, the DC12V power supply is further connected to a DC-DC power module U2, the DC-DC power module U2 outputs a DC5V power supply again, and the DC12V power supply and the DC5V power supply provide power for the CPU and other units.
The utility model adopts the new power supply design scheme to use the number of devices (about 10) which is greatly reduced compared with the number of devices (about 60) of the conventional switching power supply scheme, and has smaller volume and lower failure rate.
The above embodiments are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of the present invention is not limited to the above embodiments. The methods used in the above examples are conventional methods unless otherwise specified.
Claims (3)
1. A high-precision electric power monitor comprises a CPU, an alternating current signal acquisition unit, a storage unit, an analog quantity transmission output unit and a display unit which are connected with ports of the CPU, and a power supply unit; the device is used for acquiring three-phase alternating current voltage and current signals, displaying, transmitting and outputting the signals;
the analog quantity transmission output unit is characterized by comprising a magnetic isolator, a resistance-capacitance filter circuit, a voltage-current conversion circuit and a current amplification circuit which are sequentially connected from an input end to an output end, wherein the magnetic isolator receives a PWM signal output by a CPU and outputs the isolated PWM signal, and meanwhile, the magnetic isolator also outputs an isolated grounding signal TGND which is used as a common grounding signal of the resistance-capacitance filter circuit, the voltage-current conversion circuit and the current amplification circuit.
2. A high accuracy electrical power monitoring instrument as in claim 1 wherein the magnetic isolator is ADuM 1200.
3. A high accuracy power monitor as claimed in claim 1, wherein said power supply unit comprises an AC-DC power module and a DC-DC power module connected in sequence from input to output, the input of the AC-DC power module is connected to an AC220V power supply, the output of the AC-DC power module outputs a DC12V power supply, and at the same time, the DC12V power supply is further connected to the DC-DC power module, the DC-DC power module outputs a DC5V power supply again, and the DC12V power supply and the DC5V power supply provide power for the CPU.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121662321.XU CN215910552U (en) | 2021-07-21 | 2021-07-21 | High-precision electric power monitor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121662321.XU CN215910552U (en) | 2021-07-21 | 2021-07-21 | High-precision electric power monitor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN215910552U true CN215910552U (en) | 2022-02-25 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202121662321.XU Active CN215910552U (en) | 2021-07-21 | 2021-07-21 | High-precision electric power monitor |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN215910552U (en) |
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2021
- 2021-07-21 CN CN202121662321.XU patent/CN215910552U/en active Active
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