CN115656610B - Device and method for measuring current of silicon controlled branch of excitation system - Google Patents
Device and method for measuring current of silicon controlled branch of excitation system Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 46
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 46
- 239000010703 silicon Substances 0.000 title claims abstract description 46
- 230000005284 excitation Effects 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 12
- 230000005347 demagnetization Effects 0.000 claims abstract description 16
- 238000006243 chemical reaction Methods 0.000 claims abstract description 11
- 230000002457 bidirectional effect Effects 0.000 claims description 18
- 238000005070 sampling Methods 0.000 claims description 16
- 230000000087 stabilizing effect Effects 0.000 claims description 12
- 230000002441 reversible effect Effects 0.000 abstract description 10
- 238000001514 detection method Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
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- 230000007547 defect Effects 0.000 description 2
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- 230000007774 longterm Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
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- 239000000126 substance Substances 0.000 description 1
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Abstract
The invention discloses a device and a method for measuring the current of a silicon controlled branch of an excitation system, wherein the device comprises: the current input module comprises a current transformer and an input circuit, and the current input module is used for connecting the three-phase fully-controlled bridge type silicon controlled rectifier circuit to obtain branch current; the demagnetization module comprises a demagnetization circuit and is connected with the current input module so as to demagnetize the current transformer; and the voltage output module comprises a conversion circuit, and the voltage conversion module is connected with the input module so as to convert the secondary output current of the current transformer into corresponding voltage and output the voltage. According to the invention, the current input module, the demagnetization module and the voltage output module are arranged, the thyristor branch current is converted into corresponding voltage, demagnetization is realized through reverse voltage, and the thyristor branch current can still be accurately and stably measured under extreme conditions.
Description
Technical Field
The invention relates to the technical field of silicon controlled branch current detection in an excitation system, in particular to a silicon controlled branch current measuring device and method for the excitation system.
Background
At present, in a static silicon controlled excitation system of a synchronous motor, a power rectification part usually adopts a three-phase fully-controlled bridge type silicon controlled rectification circuit. Because of the unidirectional conductivity of the controllable silicon, the current flowing through the controllable silicon branch circuits is unidirectional current, the number of the controllable silicon is six, and the six controllable silicon are respectively + A, -A, + B, -B, + C and-C, and the flowing direction of the current of each controllable silicon branch circuit is shown in figure 1.
When the A-phase current IA flows out of the + A controllable silicon, current IA +; the IA generates a current IA-when flowing back from the-A thyristor. The B-phase current IB and the C-phase current IC are equal to IA. When the three-phase fully-controlled bridge type rectifying circuit normally runs, the IA, IB and IC currents are in positive and negative symmetry, and the single-phase current outputs 120 degrees in a positive direction and 120 degrees in a negative direction. For the example of IA, the current waveform is shown in FIG. 2. In fig. 2, the IA current waveform period is composed of T1, T2, T3, and T4. Wherein, the time of the T1 stage and the T3 stage is equal, the current is 0, and the corresponding electrical angle is 60 degrees; the T2 stage is a + A silicon controlled rectifier conduction stage, and the corresponding electrical angle is 120 degrees; the T4 stage is a-A silicon controlled rectifier conduction stage, and the corresponding electrical angle is 120 degrees. When the three-phase fully-controlled bridge rectifier circuit works normally, IA + is equal to IA-. However, when a plurality of three-phase fully-controlled bridge rectifier circuits are connected in parallel, the situation may change. When two three-phase fully-controlled bridge rectifier circuits work in parallel, taking phase a as an example, two + phase a silicon controlled rectifiers run in parallel and two-phase a silicon controlled rectifiers run in parallel, as shown in fig. 3, a schematic diagram of parallel operation of rectifier bridges is shown.
As can be seen from FIG. 3, the total forward current of phase A is composed of IA + and IA2+, and the total reverse current of phase A is composed of IA-and IA 2-. Due to the inconsistency of the characteristics of the + A controllable silicon and the + A2 controllable silicon, the IA + current amplitude and the IA2+ current amplitude cannot be equal at any moment. Similarly, the IA-and IA 2-current amplitudes are not guaranteed to be equal at any time. Under extreme conditions, the IA + current sharing may be even larger, and the IA-current output is 0, and the IA current waveform is shown in fig. 4. Under the extreme condition shown in fig. 4, the detection of the IA exciting current of the thyristor also needs to be accurate and reliable.
In the current detection means of the thyristor branch, a common method is to install hall sensors in corresponding phases. For example, a Hall sensor is additionally arranged on the phase A, and the actual current passing through the + A controllable silicon and the actual current passing through the-A controllable silicon can be obtained by separating IA + and IA-of output signals of the Hall sensor and calculating. Due to the problems of high cost, poor overload capability, easy damage, aging and zero drift caused by long-term use and the like, the Hall sensor is not an ideal current detection device for the silicon controlled branch.
Another approach is to use a conventional current transformer to detect the thyristor branch current. Compared with a Hall sensor, the current transformer has high reliability and low cost. When the current transformer is used for detecting the current of the branch circuit, taking phase A as an example, when IA + and IA-are in a balanced state, the actual current passing through + A controllable silicon and-A controllable silicon can still be obtained by separating IA + and IA-of the output signal of the current transformer and calculating. If the IA + and IA-currents are unbalanced, even under the extreme operating conditions shown in fig. 4, it can be seen from fig. 4 that the IA current has a dc component. The direct current component causes magnetic bias and even saturation of an iron core of the current transformer, so that nonlinear output of the current transformer is caused, and the actual current of the thyristor branch cannot be reflected.
Therefore, it is highly desirable to provide a measuring device which is suitable for an excitation system and can accurately and stably measure the current of the thyristor branch circuit under the condition that a plurality of rectifier bridges are operated in parallel.
Disclosure of Invention
In order to overcome the technical defect that the current measurement of the thyristor branch of the existing excitation system is inaccurate under extreme conditions, the invention provides a device and a method for measuring the current of the thyristor branch of the excitation system.
In order to solve the problems, the invention is realized according to the following technical scheme:
in a first aspect, the present invention discloses a thyristor branch current measuring device of an excitation system, comprising:
the current input module comprises a current transformer and an input circuit, and the current input module is used for connecting the three-phase fully-controlled bridge type silicon controlled rectifier circuit to obtain branch current;
the demagnetization module comprises a demagnetization circuit and is connected with the current input module so as to demagnetize the current transformer;
and the voltage output module comprises a conversion circuit, and is connected with the input module so as to convert the secondary output current of the current transformer into corresponding voltage and output the voltage.
As a preferred implementation of the present invention, the sampling switching module includes a sampling switching circuit, and the sampling switching module is connected to the voltage output module, and implements sampling switching between a large current and a small current by using a two-stage resistor series connection manner.
As a preferred implementation of the present invention, the current transformer in the current input module is close to one of the thyristors in the three-phase fully controlled bridge thyristor rectification circuit in the excitation system, so as to sense the current of the thyristor branch.
As a preferred implementation of the present invention, the input circuit comprises a set of diodes D1 and D3 connected in series and facing inward, and a set of diodes D2 and D4 connected in series and facing outward, the two sets of diodes being connected in parallel.
As a preferred implementation of the present invention, the degaussing circuit includes a transistor Q1, a transistor Q2, a diode D7, a diode D8, a diode D9, a resistor R2, and a resistor R4;
one end of the degaussing circuit is connected between the diode D1 and the diode D3, and the other end of the degaussing circuit is connected between the diode D2 and the diode D4.
In a preferred embodiment of the present invention, in the degaussing circuit, an emitter of the transistor Q1 is connected between the diode D1 and the diode D3, one end of the resistor R2 is connected to a base of the transistor Q1, the other end of the resistor R2 is connected to an emitter of the transistor Q1, the diode D7 and the diode D8 are arranged in parallel between a collector of the transistor Q1 and a collector of the transistor Q2, the collector of the transistor Q2 is further connected to the base of the transistor Q1, the diode D9 and the resistor R4 are connected in series and between the collector and the emitter of the transistor Q2, and the emitter of the transistor Q2 is connected between the diode D2 and the diode D4.
As a preferred implementation of the present invention, the switching circuit includes a resistor R1, a bidirectional zener diode D5, and a bidirectional zener diode D6 connected in parallel to each other, one end of the resistor R1, one end of the bidirectional zener diode D5, and one end of the bidirectional zener diode D6 are respectively connected to the current transformer, and the connection between the bidirectional zener diode D5 and the bidirectional zener diode D6 is connected to the connection between the diode D3 and the diode D4.
In a preferred embodiment of the present invention, the sampling switching circuit is connected to the conversion circuit, and includes a resistor R3, a diode D10, a diode D11, a diode D12, and a diode D13, wherein the diode D10 and the diode D11 are connected in series and oriented in the same direction, the diode D12 and the diode D13 are connected in parallel and oriented in the same direction, the diode D10 and the diode D12 are oriented in opposite directions, the resistor R3 is connected in parallel to each of the two groups of diodes, the resistor R3 is connected to the resistor R1, and the resistor R3 is grounded to the resistor R1.
In a second aspect, the invention also discloses a method for measuring the current of the thyristor branch of the excitation system, which comprises the following steps:
acquiring secondary current of a current transformer;
based on the intermittent period of the turn-off of the controlled silicon, the secondary current is reversely demagnetized;
if the current is larger than a preset value, acquiring the voltage at two ends of the resistor R1;
if the current is not greater than the preset value, acquiring the voltage at two ends of the resistor R3;
and outputting the collected secondary voltage signal.
Compared with the prior art, the invention has the beneficial effects that:
the invention converts the thyristor branch current into corresponding voltage by creatively arranging the current input module, the demagnetization module and the voltage output module, realizes demagnetization by reverse voltage, and can still accurately and stably measure the thyristor branch current in a structure in which a plurality of rectifier bridges are connected in parallel and under extreme conditions.
Drawings
Embodiments of the invention are described in further detail below with reference to the attached drawing figures, wherein:
FIG. 1 is a schematic diagram of a three-phase fully-controlled bridge type silicon controlled rectifier circuit of an excitation system in the prior art;
FIG. 2 is a schematic current waveform of a prior art thyristor branch current;
FIG. 3 is a schematic diagram of a prior art parallel operation of rectifier bridges of an excitation system;
FIG. 4 is a schematic diagram of a DC component of an excitation system measured by a current transformer in an extreme condition in the prior art;
FIG. 5 is a schematic structural diagram of a thyristor branch current measuring device of an excitation system of the invention;
FIG. 6 is a schematic flow chart of a method for measuring the current of the thyristor branch of the excitation system of the present invention;
in the figure:
the device comprises an M1-current input module, an M2-demagnetization module, an M3-voltage output module and an M4-sampling switching module.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it should be understood that they are presented herein only to illustrate and explain the present invention and not to limit the present invention.
The detailed features and advantages of the invention are described in detail in the following detailed description, which is sufficient for any person skilled in the art to understand the technical contents of the invention and to implement the invention, and the objects and advantages related to the invention can be easily understood by any person skilled in the art according to the disclosure of the present specification, the claims and the accompanying drawings. The following examples are intended to further illustrate aspects of the present invention in detail, but are not intended to limit the scope of the present invention in any way.
In the following description, for the purpose of simplicity and clarity of the drawing, some conventional structures and elements may be shown in the drawings, and some features of the drawings may be slightly enlarged or changed in scale or size to achieve the purpose of facilitating understanding and viewing of the technical features of the invention, but the invention is not limited thereto. In addition, coordinate axes are provided in the drawings to facilitate understanding of the relative positional relationship and the actuation direction of the elements.
It is to be understood that the terms "upper", "lower", and the like, as used herein, are intended to refer to particular orientations and relationships thereof, and are used merely to facilitate describing the invention and to simplify the description, but do not indicate or imply that the referenced devices or components must be constructed and operated in a particular orientation and therefore should not be considered limiting. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements.
Furthermore, the terms "end," "section," "portion," "region," "section," and the like may be used hereinafter to describe a particular feature or feature in or on a particular element or structure, but are not limited to such terms. The term "and/or" may also be used hereinafter to refer to a combination including one or all of one or more of the associated listed elements or structures. Furthermore, the terms "substantially", "about" or "approximately" may also be used hereinafter in connection with ranges of dimensions, concentrations, temperatures or other physical or chemical properties or characteristics, and are intended to cover deviations that may exist in the upper and/or lower limits of the ranges of properties or characteristics, or that represent acceptable deviations from manufacturing tolerances or from analytical procedures that allow for the desired results.
Furthermore, unless otherwise defined, all terms or phrases used herein, including technical and scientific terms and terms, include their ordinary meanings and meanings as understood by those skilled in the art. Furthermore, the definitions of the above-mentioned words or terms should be construed in this specification to include meanings consistent with the technical fields related to the present invention. Unless specifically defined, these terms and phrases are not to be construed in an idealized or formal sense unless expressly so defined.
In the current detection means for the thyristor branch, a hall sensor is usually installed in the corresponding phase. For example, a Hall sensor is additionally arranged on the phase A, and the actual current passing through the + A controllable silicon and the actual current passing through the-A controllable silicon can be obtained by separating IA + and IA-of output signals of the Hall sensor and calculating. Due to the problems of high cost, poor overload capability, easy damage, aging and zero drift caused by long-term use and the like, the Hall sensor is not an ideal current detection device for the silicon controlled branch.
Another approach is to use a conventional current transformer to sense the thyristor leg current. Compared with a Hall sensor, the current transformer has high reliability and low cost. When the current transformer is used for detecting the current of the branch circuit, taking phase A as an example, when IA + and IA-are in a balanced state, the actual current passing through + A controllable silicon and-A controllable silicon can still be obtained by separating IA + and IA-of the output signal of the current transformer and calculating. If the IA + and IA-currents are unbalanced, even under the extreme operating conditions shown in fig. 4, it can be seen from fig. 4 that the IA current has a dc component. The direct current component causes magnetic bias and even saturation of an iron core of the current transformer, nonlinear output of the current transformer is caused, and actual current of the thyristor branch cannot be reflected.
Therefore, the invention aims to solve the technical defect that the actual current of the silicon controlled branch circuit cannot be reflected when a plurality of rectifier bridges in an excitation system run in parallel and extreme working conditions occur in the prior art.
Example 1
Fig. 5 shows a preferred structure of the thyristor branch current measuring device of the excitation system according to the present invention.
In a first aspect, the present invention discloses a thyristor branch current measuring device of an excitation system, comprising:
the current input module M1 comprises a current transformer and an input circuit, and the current input module M1 is used for connecting a three-phase fully-controlled bridge type silicon controlled rectifier circuit to obtain branch current;
the demagnetization module M2 comprises a demagnetization circuit, and the demagnetization module M2 is connected with the current input module M1 to demagnetize the current transformer;
and the voltage output module M3 comprises a conversion circuit, and the voltage output module M3 is connected with the current input module M1 so as to convert the secondary output current of the current transformer into corresponding voltage and output the voltage.
Further comprising:
and the sampling switching module M4 comprises a sampling switching circuit, the sampling switching module M4 is connected with the voltage output module M3, and the sampling switching between large current and small current is realized by adopting a mode of connecting two-stage resistors in series.
As a preferred implementation of the present invention, the current transformer in the current input module M1 is close to one of the thyristors in the three-phase fully controlled bridge thyristor rectification circuit in the excitation system to sense the current of the thyristor branch, the input circuit includes a set of diodes D1 and D3 connected in series and facing inward, and a set of diodes D2 and D4 connected in series and facing outward, and the two sets of diodes are connected in parallel. The degaussing circuit comprises a triode Q1, a triode Q2, a diode D7, a diode D8, a diode D9, a resistor R2 and a resistor R3; one end of the degaussing circuit is connected between the diode D1 and the diode D3, and the other end of the degaussing circuit is connected between the diode D2 and the diode D4.
In a preferred embodiment of the present invention, in the degaussing circuit, an emitter of the transistor Q1 is connected between the diode D1 and the diode D3, one end of the resistor R2 is connected to a base of the transistor Q1, the other end of the resistor R2 is connected to an emitter of the transistor Q1, the diode D7 and the diode D8 are arranged in parallel between a collector of the transistor Q1 and a collector of the transistor Q2, the collector of the transistor Q2 is further connected to the base of the transistor Q1, the diode D9 and the resistor R3 are connected in series between the collector and the emitter of the transistor Q2, and the emitter of the transistor Q2 is connected between the diode D2 and the diode D4. The conversion circuit comprises a resistor R1, a bidirectional voltage stabilizing diode D5 and a bidirectional voltage stabilizing diode D6 which are connected in parallel, one end of the resistor R1, one end of the bidirectional voltage stabilizing diode D5 and one end of the bidirectional voltage stabilizing diode D6 are respectively connected with the current transformer, and the bidirectional voltage stabilizing diode D5 and the bidirectional voltage stabilizing diode D6 are connected with the diode D3 and the diode D4. The sampling switching circuit is connected with the conversion circuit and comprises a resistor R3, a diode D10, a diode D11, a diode D12 and a diode D13, wherein the diode D10 and the diode D11 are connected in series and have the same orientation, the diode D12 and the diode D13 are connected in parallel and have the same orientation, the orientations of the diode D10 and the diode D12 are opposite, the resistor R3 is connected with the two groups of diodes in parallel, the resistor R3 is connected with the resistor R1, and the resistor R3 and the resistor R1 are grounded.
The device measures the current of the silicon controlled branch circuit based on the current transformer mode, and according to the characteristic that the three-phase bridge rectifier circuit has T1 and T3 silicon controlled rectifier turn-off intermittent periods shown in figure 2, the current transformer is reversely demagnetized by utilizing the T1 and T3 intermittent periods, so that the current transformer always works in a linear region, and the purpose of accurately measuring the current of the silicon controlled branch circuit is achieved.
The main functions of the device are as follows: converting the secondary output current of the current transformer into voltage; and carrying out demagnetization treatment on the current transformer.
Taking the phase a current as an example, when the + a thyristor is turned on, the secondary induced current I of the current transformer flows out from bottom to top, and flows back to the current transformer through the diode D1, the triodes Q1 and Q2, the diode D4 and the resistor R1. When the-A thyristor is conducted, the secondary induction current I of the current transformer flows out from top to bottom, sequentially flows through the resistor R1, the diode D3, the triode Q1, the triode Q2 and the diode D2 and flows back to the current transformer. After the current I flows through the resistor R1, a voltage U is generated across the resistor R1. The voltage output can be used for calculating the actual current values of the + A controllable silicon and the-A controllable silicon according to the amplitude and the positive and negative directions of the voltage U.
Another function of the degaussing module M2 is to degauss the current transformer. When the + A thyristor switches from on to off, the output current of the current transformer is rapidly reduced. When the output current of the current transformer is smaller than the minimum conducting current of the triode Q1 and the triode Q2, the positive output current of the current transformer is suddenly cut off. Meanwhile, a reverse voltage is induced by the leakage inductance of the current transformer coil. The reverse voltage forms a path through the resistor R1, the diode D3, the resistor R2, the zener diode D9, the resistor R4, and the diode D2. The path generates higher reverse voltage to provide conditions for reverse demagnetization of the current transformer. Meanwhile, 60-degree cut-off time exists after the + A thyristor is cut off, and the reverse voltage can be just demagnetized. When the-A thyristor is switched on and off, the principle of generating reverse degaussing voltage is consistent with the principle of the + A thyristor.
The operating principle of the thyristor branch current measuring device of the excitation system is as follows:
the invention converts the current of the silicon controlled rectifier branch circuit into corresponding voltage by creatively arranging the current input module M1, the degaussing module M2 and the voltage output module M3, realizes degaussing through reverse voltage, and can still accurately and stably measure the current of the silicon controlled rectifier branch circuit in a structure that a plurality of rectifier bridges are connected in parallel and under extreme conditions.
The current transformer converts the induced current of the current transformer into voltage for output, has the function of degaussing the current transformer, realizes the sampling switching of large current and small current by adopting a two-stage resistor series connection mode, and utilizes the inductance induction of a secondary coil of the current transformer to generate specific counter voltage in the process of the primary current of the current transformer being attenuated to zero so as to achieve the aim of degaussing and anti-saturation of the current transformer.
Other structures of the thyristor branch current measuring device of the excitation system described in the embodiment are referred to in the prior art.
Example 2
In a second aspect, as shown in fig. 6, the present invention further discloses a method for measuring a current of a thyristor branch of an excitation system, including the following steps:
step S1: acquiring secondary current of the current transformer;
step S2: based on the intermittent period of the turn-off of the controlled silicon, the secondary current is reversely demagnetized;
and step S3: if the current is larger than a preset value, acquiring the voltage at two ends of the resistor R1;
and step S4: if the current is not greater than the preset value, acquiring the voltage at two ends of the resistor R3;
step S5: and outputting the collected secondary voltage signal.
The method for measuring the thyristor branch current of the excitation system disclosed by the invention is applied to the thyristor branch current measuring device of the excitation system disclosed by the embodiment 1, and all steps are completed through the structure of the device, so that the secondary voltage signal of the thyristor branch current is obtained, and stable and accurate thyristor current measurement data can be obtained under the extreme working condition of the excitation system.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, so that any modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (5)
1. The utility model provides an excitation system's silicon controlled rectifier branch current measuring device which characterized in that includes:
the current input module comprises a current transformer and an input circuit, and the current input module is used for connecting the three-phase fully-controlled bridge type silicon controlled rectifier circuit to obtain branch current;
the demagnetization module comprises a demagnetization circuit and is connected with the current input module so as to demagnetize the current transformer;
the voltage output module comprises a conversion circuit, and the voltage conversion module is connected with the current input module so as to convert the secondary output current of the current transformer into corresponding voltage and output the voltage;
the degaussing circuit comprises a triode Q1, a triode Q2, a diode D7, a diode D8, a diode D9, a resistor R2 and a resistor R4;
the input circuit comprises a group of diodes D1 and D3 which are connected in series and face inwards relatively, and a group of diodes D2 and D4 which are connected in series and face outwards relatively, wherein the two groups of diodes are connected in parallel;
one end of the degaussing circuit is connected between the diode D1 and the diode D3, and the other end of the degaussing circuit is connected between the diode D2 and the diode D4;
in the demagnetization circuit, an emitting electrode of a triode Q1 is connected between a diode D1 and a diode D3, one end of a resistor R2 is connected with a base electrode of the triode Q1, the other end of the resistor R2 is connected with the emitting electrode of the triode Q1, a diode D7 and a diode D8 are arranged between a collector electrode of the triode Q1 and a collector electrode of the triode Q2 in parallel, the collector electrode of the triode Q2 is further connected with the base electrode of the triode Q1, a diode D9 and a resistor R4 are connected in series and connected between the collector electrode and the emitting electrode of the triode Q2, and the emitting electrode of the triode Q2 is connected between the diode D2 and the diode D4.
2. The thyristor branch current measuring device of an excitation system according to claim 1, further comprising:
and the sampling switching module comprises a sampling switching circuit, is connected with the voltage output module and realizes sampling switching between large current and small current by adopting a mode of connecting two-stage resistors in series.
3. The thyristor branch current measuring device of an excitation system according to claim 2, wherein:
and a current transformer in the current input module is close to one of the thyristors in the three-phase fully-controlled bridge type thyristor rectification circuit in the excitation system so as to induce the current of the thyristor branch.
4. The thyristor branch current measuring device of an excitation system according to claim 3, wherein:
the conversion circuit comprises a resistor R1, a bidirectional voltage stabilizing diode D5 and a bidirectional voltage stabilizing diode D6 which are connected in parallel, one ends of the resistor R1, the bidirectional voltage stabilizing diode D5 and the bidirectional voltage stabilizing diode D6 are respectively connected with the current transformer, and the other ends of the resistor R1, the bidirectional voltage stabilizing diode D5 and the bidirectional voltage stabilizing diode D6 are connected with a diode D3 and a diode D4;
the sampling switching circuit is connected with the conversion circuit and comprises a resistor R3, a diode D10, a diode D11, a diode D12 and a diode D13, wherein the diode D10 and the diode D11 are connected in series and have the same orientation, the diode D12 and the diode D13 are connected in parallel and have the same orientation, the orientation of the diode D10 is opposite to that of the diode D12, the resistor R3 is respectively connected with the two groups of diodes in parallel, the resistor R3 is connected with the resistor R1, and the resistor R3 is grounded with the resistor R1.
5. The thyristor branch current measuring device of an excitation system according to claim 4, wherein the measuring method specifically comprises the following steps:
acquiring secondary current of the current transformer;
based on the intermittent period of the turn-off of the controlled silicon, the secondary current is reversely demagnetized;
if the current is larger than a preset value, acquiring the voltage at two ends of the resistor R1;
if the current is not greater than the preset value, acquiring the voltage at two ends of the resistor R3;
and outputting the collected secondary voltage signal.
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| US4314193A (en) * | 1980-05-22 | 1982-02-02 | Motorola, Inc. | Field coil fault detector for automotive alternator battery charging systems |
| EP2017633B1 (en) * | 2006-04-28 | 2012-08-22 | Advantest Corporation | Power applying circuit and testing apparatus |
| CN104931758B (en) * | 2014-03-21 | 2018-03-27 | 上海电科电器科技有限公司 | Direct current residual current detection device |
| CN205749664U (en) * | 2016-06-30 | 2016-11-30 | 黄德英 | Power test system |
| CN213517284U (en) * | 2020-08-12 | 2021-06-22 | 科华恒盛股份有限公司 | Current sampling circuit |
| CN114113762A (en) * | 2021-10-28 | 2022-03-01 | 上海金智晟东电力科技有限公司 | Active zero magnetic flux sampling device |
| CN114333657B (en) * | 2021-12-10 | 2024-02-06 | 北京镁伽科技有限公司 | Current sampling system, adjustable voltage source and image signal generator |
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