CN111903214B - Low-frequency large-current sensor - Google Patents
Low-frequency large-current sensor Download PDFInfo
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- CN111903214B CN111903214B CN200910125305.4A CN200910125305A CN111903214B CN 111903214 B CN111903214 B CN 111903214B CN 200910125305 A CN200910125305 A CN 200910125305A CN 111903214 B CN111903214 B CN 111903214B
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Abstract
The invention discloses a low-frequency large-current sensor which comprises a Rockwell coil, a first amplifying circuit, an integrating circuit, a second amplifying circuit and a data processor, wherein the Rockwell coil is connected with the first amplifying circuit; the two ends of the Rockwell coil are divided by interfacesIs connected with a sampling resistor RTTwo ends, to sample the resistor RTThe terminal voltage is transmitted to a first amplifying circuit through a double-core shielding wire, the first amplifying circuit amplifies the acquired electric signal and transmits the amplified electric signal to an integrating circuit, the output end of the integrating circuit is connected with a second amplifying circuit, and the output end of the second amplifying circuit is connected with a data processor. The sensor can accurately measure large current with frequency ranging from 1 Hz to hundreds of Hz and continuously changing. The defect of low accuracy when the conventional Rogowski coil measures low-frequency large current is overcome; the accuracy is better than 0.3% -0.5%, the power consumption is small, the temperature additional error is less than 0.1%/10 ℃, the anti-magnetic interference capability is strong, the structure is simple, the weight is light, the price is low, the interchangeability is strong, and the installation, the calibration, the debugging and the maintenance are convenient.
Description
Technical Field
The invention relates to a low-frequency large-current sensor which is suitable for solving the problem of real-time monitoring of low-frequency large current in the following aspects: the current feedback, the cut-off control, the current stabilization regulation in the power electronic equipment, the overcurrent protection at the AC side in the power conversion device, the bus current in systems such as an electric power system, a linear motor and a rotating motor and the like ensure that related systems can run healthily, safely and reliably.
Background
The converter based on sine wave pulse width modulation (SPWM) and vector control algorithm is widely applied to alternating current transmission and other energy conversion systems due to the remarkable characteristics that the converter has high power factor, can simultaneously realize frequency conversion and voltage transformation, decoupling control and closed-loop control of flux and torque of an asynchronous motor and the like.
The linear induction motor is used as an actuating mechanism in an electromagnetic transmitting device, and adopts a variable-frequency speed regulating device based on the technology. Research shows that the device has the following typical characteristics:
(1) high voltage levels (several kilovolts) and non-sinusoidal waveforms; (2) the current amplitude is strong (tens of kiloamperes); (3) the frequency varies continuously (1 hz-several hundred hz).
According to the literature, for pulse width modulated converters, zero sequence components, i.e. common mode voltages, are present at the machine terminal voltages. This common mode voltage, through capacitive coupling between the primary and secondary, produces a large current to ground which directly affects the motor and associated electrical equipment. Moreover, the quality of vector control depends on how accurate the motor parameters are. Therefore, when the inverter drags the linear induction motor, how to rapidly and accurately extract the electrical parameters such as the primary and secondary resistances and the leakage inductance of the motor is very critical, and the low-frequency large current in the system must be accurately detected to accurately obtain the parameters.
The Hall current sensor is a new generation industrial current sensor developed based on Hall effect, which is essentially a current-magnetism-voltage converter, and the input and the output of the Hall current sensor have good electric isolation, and the Hall current sensor is characterized in that: the high-precision high-linearity high-frequency-band filter has the advantages of high precision, good linearity, wide frequency band, quick response, strong overload capacity, simple structure, easiness in installation and the like. At present, a Hall current sensor is generally adopted for most variable frequency speed regulation devices. The advantage is very obvious for the situation that the amplitude is only a few kiloamperes and the voltage level is not too high. However, as the current intensity and voltage level are further increased, isolation measures are required for the power supply required by the hall current sensor in order to ensure the reliability of the measuring system.
The Rogowski coil has a magnetic circuit without iron core, and is an air core coil with a special structure, which is also called an air core mutual inductor. Because the magnetic circuit of the device does not contain an iron core, the device has no saturation problem, good transient performance, wide frequency band and small influence by the external magnetic field and the position of the current-carrying conductor to be measured; the high-voltage current sensor has the advantages of good insulation with a high-voltage loop, simple structure, easy processing and the like, and can accurately measure large current by matching with a subsequent processing circuit; and with the further improvement of the current intensity and the voltage grade, the power supply required by the subsequent processing circuit does not need to be specially isolated. However, since the subsequent integration processing circuit is prone to saturation at low frequency, measures to prevent the integrator from being saturated are often required to avoid affecting the accuracy of the test system.
Disclosure of Invention
The present invention is directed to overcome the above-mentioned deficiencies of the prior art and to provide a low frequency high current sensor, which can accurately measure a continuously variable high current with a frequency of 1 hz to several hundred hz.
To achieve the aboveThe technical scheme adopted by the invention is as follows: the low-frequency high-current sensor comprises a Rockwell coil, a first amplifying circuit, an integrating circuit, a second amplifying circuit and a data processor; two ends of the Rockwell coil are respectively connected with a sampling resistor R through interfacesTTwo ends, to sample the resistor RTThe terminal voltage is transmitted to a first amplifying circuit through a double-core shielding wire, the first amplifying circuit amplifies the obtained electric signal and transmits the amplified electric signal to an integrating circuit, the output end of the integrating circuit is connected with a second amplifying circuit, and the output end of the second amplifying circuit is connected with a data processor;
the first amplifying circuit has the structure that: resistance RA1One end of the resistor R is used as a main input end of the first amplifying circuit and is connected with the double-core shielding wireA1And the other end of the resistor R is connected to a first input terminal of a first amplifier U1A2Is connected to a first input terminal of a first amplifier U1, a resistor RA2The other end of the first amplifier U1, a capacitor CT1Is connected to the output of the first amplifier U1, a capacitor CT1The other end of (3) is grounded, and a resistor RP1Is connected to the second input terminal of the first amplifier U1, a resistor RP1The other end of the first amplifier circuit is grounded and is used as the other main input end of the first amplifier circuit and is connected with the double-core shielding wire, and a capacitor CN1Is connected to the negative power supply terminal of the first amplifier U1, a capacitor CN1The other end of which is grounded, a capacitor CP1Is connected to the positive power supply terminal of the first amplifier U1, a capacitor CP1The other end of the first amplifier U1 is connected to ground, and the negative power supply of the first amplifier U1 is connected to a power supply-VCC1The positive power terminal of the first amplifier U1 is connected with a power supply + VCC1The first amplifying circuit samples the resistance R from the Rockwell coilTThe terminal voltage is transmitted to the integrating circuit after being subjected to filtering and amplification pretreatment.
The preferred structure of the integrating circuit is: capacitor C1One end of the first amplifier circuit is connected with one output end of the first amplifier circuit and the capacitor C1Another end of (2) is connected with a resistor RA3One terminal of (1), resistance RA3And the other end of the second amplifier U2 is connected to the first input end of the second amplifier U2, a capacitor C3Are connected in parallel to a first input terminal and an output terminal of U2, a resistor RA4Is connected to a first input terminal of a second amplifier U2, a resistor RA4Is connected to a node (M1) and a resistor RA5One terminal of which is connected to the output terminal of the second amplifier U2, a resistor RA5Another terminal of the resistor R is connected to a node M1A6Is connected to node M1, resistor RA6Another terminal of the capacitor C2One terminal of (C), a capacitor2The other end of the resistor R is connected to the groundP2Is connected to the second input terminal of the second amplifier U2, a resistor RP2Is grounded and connected with the other output end of the first amplifying circuit, and a capacitor CN2Is connected to the negative power supply terminal of the second amplifier U2, a capacitor CN2The other end of which is grounded, a capacitor CP2Is connected to the positive power supply terminal of the second amplifier U2, a capacitor CP2The other end of the second amplifier U2 is connected to ground, and the negative power supply of the second amplifier U2 is connected to the power supply-VCC1The positive power terminal of the second amplifier U2 is connected with a power supply + VCC1Capacitor CT2Is connected to the output of the second amplifier U2, a capacitor CT2The other end of the second amplifier is grounded, and the integrating circuit carries out integration reduction processing on the electric signal from the first amplifier and then transmits the electric signal to the second amplifier.
The preferred structure of the second amplifying circuit is: resistance RA7Is connected to an output of the integrating circuit, a resistor RA7And the other end of the resistor R is connected to the first input terminal of the third amplifier U3A8Is connected to the first input terminal of the third amplifier U3, a resistor RA8And the other end of the third amplifier U3, a capacitor CT3Is connected to the output of the third amplifier U3, a capacitor CT3The other end of which is grounded, a capacitor CT4Are connected in parallel to the capacitor CT3On both ends, a resistor RP3Is connected to the second input terminal of the third amplifier U3, a resistor RP3Is grounded and connected to the other output terminal of the integrating circuit, and a capacitor CN3Is connected to the negative power supply terminal of the third amplifier U3, a capacitor CN3The other end of which is grounded, a capacitor CP3Is connected to the positive power supply terminal of the third amplifier U3, a capacitor CP3The other end of the third amplifier U3 is connected to ground, and the negative power supply of the third amplifier U3 is connected to the power supply-VCC1The positive power terminal of the third amplifier U3 is connected with a power supply + VCC1And the second amplifying circuit further amplifies the electric signal from the integrating circuit and transmits the amplified electric signal to the data processor.
The invention has the advantages that:
(1) the sensor uses a Rogowski coil without a core as a sensing head, so that the sensor has no saturation problem and has high response speed.
(2) The Rogowski coil is well electrically isolated from the tested loop, so that the Rogowski coil is particularly suitable for solving the problem of large-current measurement in a high-voltage occasion.
(3) When the amplitude of the current to be measured is lower, the same Rogowski coil can be connected in series, so that the distributed capacitance of the Rogowski coil can be reduced, the induction signal of the coil can be greatly increased, the signal-to-noise ratio of the sensor is improved, and the sensitivity of a test system is enhanced.
(4) The designed subsequent processing circuit can effectively prevent the output of the circuit from being saturated, and ensure the accuracy of measuring the large current by the Rogowski coil.
(5) The sensor is designed to be able to measure large currents with frequencies between 1 hz and several hundred hz and varying continuously.
In a word, the defect of low accuracy when the conventional Rogowski coil measures low-frequency large current is overcome; the accuracy is better than 0.3% -0.5%, the power consumption is small, the temperature additional error is less than 0.1%/10 ℃, the anti-magnetic interference capability is strong, the structure is simple, the weight is light, the price is low, the interchangeability is strong, and the installation, the calibration, the debugging and the maintenance are convenient.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment of a low-frequency high-current sensor according to the present invention.
Fig. 2 is a schematic view of the skeleton core of the Rogowski coil of fig. 1.
Fig. 3 is a schematic diagram of the amplifying circuit 4 in fig. 1.
Fig. 4 is a schematic diagram of the integrating circuit 5 in fig. 1.
Fig. 5 is a schematic diagram of the amplifying circuit 6 in fig. 1.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
As shown in fig. 1, the low frequency large current sensor provided by the present invention includes a Rogowski coil 1, an amplifying circuit 4, an integrating circuit 5, an amplifying circuit 6, and a data processor 7. The two ends of the Rogowski coil 1 are respectively connected with a sampling resistor R through interfaces T1 and T2TTwo ends, to sample the resistor RTThe terminal voltage is transmitted to an amplifying circuit 4 through a double-core shielding wire 3, the amplifying circuit 4 amplifies the obtained electric signal and transmits the amplified electric signal to an integrating circuit 5, the output end of the integrating circuit 5 is connected with an amplifying circuit 6, and the output end of the amplifying circuit 6 is connected with a data processor 7.
When in use, the Rogowski coil 1 is sleeved on the tested current bus 2. When the Rogowski coil 1 obtains an induction signal proportional to the change rate of the measured current, a sampling resistor R reflecting the induction signal is arranged through the double-core shielding wire 3TThe terminal voltage of the transformer is transmitted to an amplifying circuit 4 for preprocessing such as filtering and amplifying, and then transmitted to an integrating circuit 5 for integral reduction, so that an electric signal which is in direct proportion to the amplitude of the measured current can be obtained, the electric signal is transmitted to an amplifying circuit 6 for further amplification processing, and finally the signal is transmitted to a data processor 7 for processing, and the magnitude of the measured current is finally obtained.
The sensor can also be used for overcurrent protection, only a threshold voltage U needs to be set in the data processor 7THOnce the electrical signal obtained by the data processor 7 exceeds the threshold voltage, an alarm level can be output to provide a control instruction for performing an overcurrent protection operation.
The bobbin core of the Rogowski coil may be processed into a ring shape having a rectangular cross-section as shown in fig. 2(a), or into a ring shape having a circular cross-section as shown in fig. 2(b), and the bobbin core may be selected from a soft rubber band (or an epoxy resin rod). Since the Rogowski coil needs to be wound by one turn and led out from the center of the bobbin core during winding, a winding slot 8 needs to be formed outward from the center of the bobbin core of the Rogowski coil.
As shown in fig. 3, the amplifier circuit 4 has a structure in which: two of the two-core shielded wires 3 are connected via the interfaces T3 and T4, respectivelyInterfaces T1 and T2, interface T3 connects resistance RA1The interface T4 is grounded, and the resistor RA1Is connected to the interface T3, resistor RA1The other end of the resistor R is connected with the A2 pin of the first amplifier U1A2One end of the resistor is connected with the A2 pin of the amplifier U1 and the resistor RA2The other end of the capacitor C is connected with the A6 pin of the amplifier U1T1One terminal of the first capacitor is connected with the A6 pin of the amplifier U1 and the capacitor CT1The other end of (3) is grounded, and a resistor RP1One end of the resistor is connected with the A3 pin of the amplifier U1 and the resistor RP1The other end of which is grounded, a capacitor CN1One terminal of the first capacitor is connected with the A4 pin of the amplifier U1 and the capacitor CN1The other end of which is grounded, a capacitor CP1One terminal of the first capacitor is connected with the A7 pin of the amplifier U1 and the capacitor CP1The other end of the amplifier is grounded, and the A4 pin of the amplifier U1 is connected with a power supply-VCC1The A7 pin of the amplifier U1 is connected with a power supply + VCC1The amplifying circuit 4 samples the resistance R from the Rogowski coil 1TAfter being preprocessed by filtering and amplifying, the terminal voltage of the integrated circuit is transmitted to the integrating circuit 5 through the interfaces T5 and T6.
As shown in fig. 4, the integrating circuit 5 has a structure in which: a capacitor C connected to the output of the amplifying circuit 4 via interfaces T5 and T6T1Interface T5 and capacitor C1Is connected to the interface T6 ground, the capacitor C1Is connected to the interface T5, a capacitor C1Another end of (2) is connected with a resistor RA3One terminal of (1), resistance RA3The other end of the second amplifier U2 is connected with the A2 pin of the second amplifier U2 and a capacitor C3Is connected in parallel with the A2 pin and the A6 pin of the U2, and a resistor RA4One end of the resistor is connected with the A2 pin of the amplifier U2 and the resistor RA4Another terminal of the resistor R is connected to a node M1A5One end of the resistor is connected with the A6 pin of the amplifier U2 and the resistor RA5Another terminal of the resistor R is connected to a node M1A6Is connected to node M1, resistor RA6Another terminal of the capacitor C2One terminal of (C), a capacitor2The other end of the resistor R is connected to the groundP2One end of the resistor is connected with the A3 pin of the amplifier U2 and the resistor RP2The other end of which is grounded, a capacitor CN2One terminal of the first capacitor is connected with the A4 pin of the amplifier U2 and the capacitor CN2The other end of which is grounded, a capacitor CP2One terminal of the first capacitor is connected with the A7 pin of the amplifier U2 and the capacitor CP2At the other end ofGround, A4 pin of amplifier U2 is connected with power supply-VCC1The A7 pin of the amplifier U2 is connected with a power supply + VCC1Capacitor CT2One terminal of the first capacitor is connected with the A6 pin of the amplifier U2 and the capacitor CT2And the other end thereof is grounded, and the integrating circuit 5 performs integration and restoration processing on the electric signal from the amplifying circuit 4, and then transmits the electric signal to the amplifying circuit 6 through the interfaces T7 and T8.
As shown in fig. 5, the amplifier circuit 6 has a structure in which: a capacitor C connected to the output of the integrator circuit 5 via interfaces T7 and T8, respectivelyT2At the two ends of the connector T7, the interface T7 is connected with a resistor RA7The interface T8 is grounded, and the resistor RA7Is connected to the interface T7, resistor RA7The other end of the resistor R is connected with the A2 pin of the amplifier U3A8One end of the resistor R is connected with the A2 pin of the third amplifier U3A8The other end of the capacitor C is connected with the A6 pin of the amplifier U3T3One terminal of the first capacitor is connected with the A6 pin of the amplifier U3 and the capacitor CT3The other end of which is grounded, a capacitor CT4Are connected in parallel to the capacitor CT3On both ends, a resistor RP3One end of the resistor is connected with the A3 pin of the amplifier U3 and the resistor RP3The other end of which is grounded, a capacitor CN3One terminal of the first capacitor is connected with the A4 pin of the amplifier U3 and the capacitor CN3The other end of which is grounded, a capacitor CP3One terminal of the first capacitor is connected with the A7 pin of the amplifier U3 and the capacitor CP3The other end of the amplifier is grounded, and the A4 pin of the amplifier U3 is connected with a power supply-VCC1The A7 pin of the amplifier U3 is connected with a power supply + VCC1The amplifying circuit 6 further amplifies the electric signal from the integrating circuit 5, and then transmits to the data processor 7 via the interfaces T9 and T10.
The first to third amplifiers U1, U2, and U3 may be implemented by a chip such as OP07 or other amplifying circuit.
The data processor 7 can be used outside a common computer, and also can be a high-grade singlechip or a DSP chip or a DSP + FPGA chip or an industrial personal computer.
The above description is a preferred embodiment of the present invention, but the present invention should not be limited to the disclosure of the embodiment and the drawings. Therefore, it is intended that all equivalents and modifications which do not depart from the spirit of the invention disclosed herein are deemed to be within the scope of the invention.
Claims (3)
1. A low-frequency high-current sensor is characterized in that: the device comprises a Rockwell coil (1), a first amplifying circuit (4), an integrating circuit (5), a second amplifying circuit (6) and a data processor (7); two ends of the Rockwell coil (1) are respectively connected with a sampling resistor R through interfacesTTwo ends, to sample the resistor RTThe terminal voltage is transmitted to a first amplifying circuit (4) through a double-core shielding wire (3), the first amplifying circuit (4) amplifies and transmits the acquired electric signal to an integrating circuit (5), the output end of the integrating circuit (5) is connected with a second amplifying circuit (6), and the output end of the second amplifying circuit (6) is connected with a data processor (7); the first amplifier circuit (4) has the following structure: resistance RA1One end of the first amplifier circuit is used as a main input end of the first amplifier circuit and is connected with the double-core shielding wire (3), and the resistor RA1And the other end of the resistor R is connected to a first input terminal of a first amplifier U1A2Is connected to a first input terminal of a first amplifier U1, a resistor RA2The other end of the first amplifier U1, a capacitor CT1Is connected to the output of the first amplifier U1, a capacitor CT1The other end of (3) is grounded, and a resistor RP1Is connected to the second input terminal of the first amplifier U1, a resistor RP1The other end of the first amplifier circuit is grounded and is used as the other main input end of the first amplifier circuit and is connected with the double-core shielding wire (3), and a capacitor CN1Is connected to the negative power supply terminal of the first amplifier U1, a capacitor CN1The other end of which is grounded, a capacitor CP1Is connected to the positive power supply terminal of the first amplifier U1, a capacitor CP1The other end of the first amplifier U1 is connected to ground, and the negative power supply of the first amplifier U1 is connected to a power supply-VCC1The positive power terminal of the first amplifier U1 is connected with a power supply + VCC1The first amplifying circuit (4) samples the resistance R from the Rockwell coil (1)TThe terminal voltage of the transformer is subjected to filtering and amplification pretreatment and then transmitted to an integrating circuit (5).
2. A low frequency high current sensor according to claim 1, wherein: the structure of the integrating circuit (5) is as follows: capacitor C1One end of the first amplifying circuit (4) is connected with an output end of the first amplifying circuit, and the capacitor C1Another end of (2) is connected with a resistor RA3One terminal of (1), resistance RA3And the other end of the second amplifier U2 is connected to the first input end of the second amplifier U2, a capacitor C3Are connected in parallel to a first input terminal and an output terminal of U2, a resistor RA4Is connected to a first input terminal of a second amplifier U2, a resistor RA4Another terminal of the resistor R is connected to a node M1A5One terminal of which is connected to the output terminal of the second amplifier U2, a resistor RA5Another terminal of the resistor R is connected to a node M1A6Is connected to node M1, resistor RA6Another terminal of the capacitor C2One terminal of (C), a capacitor2The other end of the resistor R is connected to the groundP2Is connected to the second input terminal of the second amplifier U2, a resistor RP2Is grounded and is connected with the other output end of the first amplifying circuit (4), and a capacitor CN2Is connected to the negative power supply terminal of the second amplifier U2, a capacitor CN2The other end of which is grounded, a capacitor CP2Is connected to the positive power supply terminal of the second amplifier U2, a capacitor CP2The other end of the second amplifier U2 is connected to ground, and the negative power supply of the second amplifier U2 is connected to the power supply-VCC1The positive power terminal of the second amplifier U2 is connected with a power supply + VCC1Capacitor CT2Is connected to the output of the second amplifier U2, a capacitor CT2The other end of the second amplifier is grounded, and the integrating circuit (5) performs integration reduction processing on the electric signal from the first amplifying circuit (4) and then transmits the electric signal to the second amplifying circuit (6).
3. A low frequency high current sensor according to claim 1 or 2, wherein: the second amplifier circuit (6) has the following structure: resistance RA7Is connected to an output of the integrating circuit (5), and a resistor RA7And the other end of the resistor R is connected to the first input terminal of the third amplifier U3A8Is connected to the first input terminal of the third amplifier U3, a resistor RA8And the other end of the third amplifier U3, a capacitor CT3Is connected to the output of the third amplifier U3, a capacitor CT3The other end of which is grounded, a capacitor CT4Are connected in parallel to the capacitor CT3On both ends, a resistor RP3Is connected to the second input terminal of the third amplifier U3, a resistor RP3At the other end ofGround, and connected to the other output of the integrating circuit (5), a capacitor CN3Is connected to the negative power supply terminal of the third amplifier U3, a capacitor CN3The other end of which is grounded, a capacitor CP3Is connected to the positive power supply terminal of the third amplifier U3, a capacitor CP3The other end of the third amplifier U3 is connected to ground, and the negative power supply of the third amplifier U3 is connected to the power supply-VCC1The positive power terminal of the third amplifier U3 is connected with a power supply + VCC1The second amplifying circuit (6) further amplifies the electric signal from the integrating circuit (5) and transmits the amplified electric signal to the data processor (7).
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| CN200910125305.4A CN111903214B (en) | 2009-12-31 | 2009-12-31 | Low-frequency large-current sensor |
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| CN200910125305.4A CN111903214B (en) | 2009-12-31 | 2009-12-31 | Low-frequency large-current sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109188177A (en) * | 2018-10-01 | 2019-01-11 | 徐州中矿大传动与自动化有限公司 | A kind of high-power NPC three-level inverter short circuit current on-line detecting system |
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2009
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109188177A (en) * | 2018-10-01 | 2019-01-11 | 徐州中矿大传动与自动化有限公司 | A kind of high-power NPC three-level inverter short circuit current on-line detecting system |
| CN109188177B (en) * | 2018-10-01 | 2023-12-19 | 江苏国传电气有限公司 | High-power NPC three-level inverter short-circuit current on-line detection system |
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