Filter suitable for direct current signals of DEH cabinet externally connected with wave recorder

Abstract

The utility model discloses a filter suitable for a direct current signal of an external DEH cabinet of a wave recorder, and relates to the technical field of filters, in particular to the filter suitable for the direct current signal of the external DEH cabinet of the wave recorder. Comprising a functional resistor, a common mode inductor and an LC-pi type circuit. The functional resistor converts a DEH direct current signal into a voltage signal, the common-mode inductor suppresses a common-mode interference signal and does not influence a differential-mode signal, and the LC-pi type circuit further filters so as to obtain an accurate voltage signal to be measured at an output end. The filter is simple in structure and convenient to implement, can effectively convert and filter direct current signals of an external circuit of the DEH cabinet in a network-related test, ensures signal accuracy, stability and quality reliability, and has the advantages of being convenient to operate, long in service life, convenient to use and high in efficiency.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, in particular to a filter applicable to the DC signal of an external DEH cabinet of a recorder. Background Technique

[0002] In the power system network-related test, the DC signal in the DEH signal cabinet of the generator set is externally connected to the recorder for testing. However, most of the DC signals in the DEH signal cabinet are 4-20 mA current signals, and the input signal of the recorder is a DC voltage signal. The filter circuit should include a part for converting the current signal into a voltage signal. Moreover, due to external magnetic field interference and other reasons, there are common-mode signals in the circuit where the DEH is externally connected to the recorder, which affects the transmission of normal signals. Therefore, it is necessary to use a filter to filter and eliminate the interference signals during the signal transmission process.

[0003] At present, when transmitting DC signals, mainly π-type filters (including two types: RC and LC) are used for filtering. For the RC-π filter, the value of R cannot be too large, generally several to dozens of ohms. Its advantage is low cost, and its disadvantage is that the resistor consumes some energy, and the filtering effect is not as good as that of the LC-π circuit. The LC-π filter includes two capacitors and an inductor. A low-pass filter circuit is formed by connecting the first capacitor and the second capacitor in series with the input end and the output end of the inductor, and the first capacitor and the second capacitor form a parallel structure with each other. Its function is to allow the frequency signal during the normal operation of the device to enter the device, and has a great blocking effect on high-frequency interference signals. Content of the Utility Model

[0004] The purpose of the utility model is to provide a new filter circuit by adding a common-mode inductor and a functional resistor on the basis of a common LC-π filter circuit to eliminate various interference signals collected by the recorder in the network-related test and provide accurate test data for the network-related test.

[0005] To achieve the above purpose, the utility model provides the following technical solution:

[0006] A filter applicable to the DC signal of an external DEH cabinet of a recorder is provided with a filter circuit. The filter circuit includes a functional resistor, a common-mode inductor, and an LC-π circuit. The two ends of the functional resistor are respectively connected to the input interface end and are connected to the DC signal of the DEH cabinet. The common-mode inductor includes windings L11 and L12. The input ends of windings L11 and L12 are respectively connected to the two ends of the functional resistor, and the output ends of windings L11 and L12 are respectively connected to both ends of the first capacitor C11 in the LC-π circuit. Both ends of the second capacitor C12 in the LC-π circuit are the output interface ends of this filter.

[0007] The DEH DC current signal is converted into a voltage signal through a functional resistor. When the current flowing through the two ends of the functional resistor passes through the common-mode inductor, the common-mode current will cause the magnetic fluxes in the magnetic ring to be superimposed on each other, thus having a relatively large inductance, which plays an inhibitory role on the common-mode current. When the differential-mode current flows through, the magnetic fluxes in the magnetic ring cancel each other out, and there is almost no inductance. Therefore, the differential-mode current can pass through without attenuation. Thus, it can effectively suppress the common-mode interference signal without affecting the differential-mode signal normally transmitted on the line.

[0008] When the voltage signal output from the common-mode inductor passes through the first capacitor in the LC-π circuit, most of the high-frequency components will be filtered out. The series inductor also has a relatively large impedance to high-frequency signals, and the second parallel capacitor will further filter the high-frequency signals, so as to obtain an accurate voltage signal to be measured at the output end of the filter.

[0009] The described filter design meets the circuit board of the filter circuit and adapts to the direct connection between the corresponding oscillograph and the DEH cabinet wires.

[0010] The described filter also includes a filter housing. Inside the filter housing, there is a circuit board printed with a filter circuit. The two ends of the functional resistor are respectively connected with screw spring clips for connecting to the DEH cabinet wire connection; the two ends of the second capacitor C12 are respectively connected with conductive copper rings for connecting the oscillograph pen. The filter housing provides isolation protection for the filter circuit and the input and output ends to prevent external dust, water vapor, etc. from affecting the use of the filter circuit.

[0011] The surface of the filter housing is engraved with corresponding input and output engraved marks, and the marks are recessed from the surface of the housing.

[0012] The filter housing is installed through a snap design, which is convenient for installation and replacement.

[0013] Compared with the prior art, the beneficial effects of the present utility model are:

[0014] By adding a functional resistor and a common-mode inductor to the original LC-π circuit, the conversion and filtering of the DC current signal of the external circuit of the DEH cabinet in the grid-connected tests of thermal power units and hydropower units are realized. The structure is simple and easy to implement.

[0015] The DEH DC current signal is converted into a voltage signal through a functional resistor, and the common-mode inductor is used to effectively suppress the common-mode interference signal without affecting the differential-mode signal normally transmitted on the line. When the common-mode current passes through the common-mode inductor, the magnetic fluxes in the magnetic ring are superimposed on each other to generate a large inductance, while when the differential-mode current passes through, the magnetic fluxes cancel each other out and there is almost no inductance, enabling the differential-mode current to pass through without attenuation, ensuring the accuracy and stability of the signal.

[0016] The voltage signal after passing through the common-mode inductor is further filtered by an LC-π circuit. The first capacitor filters out most of the high-frequency components. The series inductor has a large impedance to high-frequency signals, and the second parallel capacitor filters the high-frequency signals again, so that an accurate voltage signal to be measured can be obtained at the output end of the filter, improving the quality and reliability of the signal.

[0017] At the input end, the filter adopts a screw spring pressing plate structure to connect with the wires of the DEH cabinet. At the output end, a conductive copper ring is used to facilitate the connection of the recording instrument pen, making the operation convenient. The designed filter housing can effectively prevent the influence of external dust and moisture on the filtering circuit, extending the service life of the filter. The input and output marks engraved on the surface of the housing are recessed from the surface of the housing, being clear and not easily worn. The housing with a snap design is convenient for installation and replacement, improving the convenience and efficiency of use. Description of the Drawings

[0018] Figure 1 It is a circuit diagram of a filter applicable to the DC signal of the recording instrument externally connected to the DEH cabinet of the present utility model;

[0019] Figure 2 It is a schematic diagram of a filter device applicable to the DC signal of the recording instrument externally connected to the DEH cabinet of the present utility model;

[0020] In the figure: 1. Functional resistor; 2. Common-mode inductor; 3. LC-π circuit; 4. Filtering circuit; 5. DEH cabinet wire; 6. Recording instrument pen; 7. Screw spring pressing plate; 8. Engraved mark; 9. Conductive copper ring. Detailed Embodiment

[0021] Next, the technical solutions in the embodiments of the present utility model will be completely described in conjunction with the accompanying drawings in the embodiments of the present utility model.

[0022] As Figure 1-2 shown, a filter applicable to the DC signal of the recording instrument externally connected to the DEH cabinet is provided with a filtering circuit 4. The filtering circuit 4 includes a functional resistor 1, a common-mode inductor 2, and an LC-π circuit 3. The two ends of the functional resistor (1) are respectively connected to the input interface ends. The common-mode inductor 2 includes windings L11 and L12. The input ends of the windings L11 and L12 are respectively connected to the two ends of the functional resistor 1. The output ends of the windings L11 and L12 are respectively connected to the two ends of the first capacitor C11 in the LC-π circuit 3. The two ends of the second capacitor C12 in the LC-π circuit 3 are the output interface ends of this filter.

[0023] The designed filter satisfies the circuit board with the filtering circuit 4 and is adapted to the direct connection between the corresponding recording instrument and the DEH cabinet wire 5.

[0024] It includes a filter housing, and a circuit board printed with a filter circuit 4 is installed inside the filter housing. Screwed spring clips 7 are respectively connected to both ends of the functional resistor 1, and the screwed spring clips 7 are respectively installed on the left and right sides of the filter housing for connection to the wires of the DEH cabinet. Conductive copper rings 9 are respectively connected to both ends of the second capacitor C12 for connection to the recording oscillograph pen 6.

[0025] Corresponding input and output engraved markings 8 are engraved on the surface of the filter housing, and the markings are recessed from the housing surface.

[0026] The filter housing is installed through a snap - fit design, which is convenient for installation and replacement.

[0027] The screwed spring clips 7 on both sides of the filter of the present utility model are input interface ends connected to the DC signal of the DEH cabinet. The DEH DC current signal is converted into a voltage signal. The input ends of the windings L11 and L12 of the common - mode inductor 2 are connected to both ends of the functional resistor 1, which can effectively suppress the common - mode interference signal without affecting the differential - mode signal. The output ends of the windings L11 and L12 are connected to both ends of the first capacitor C11 in the LC - π type circuit 3, and the conductive copper rings 9 at both ends of the second capacitor C12 in this circuit are used as the output interface ends, which can output an accurate voltage signal to be measured, facilitating the connection of the recording oscillograph pen 6.

Claims

1. A filter applicable to the DC signal of the external DEH cabinet of the oscillograph, characterized in that A filter circuit (4) is provided. The filter circuit (4) includes a functional resistor (1), a common-mode inductor (2), and an LC-π circuit (3). The two ends of the functional resistor (1) are respectively connected to the input interface terminals and are connected to the DC signal of the DEH cabinet. The common-mode inductor (2) includes windings L11 and L12. The input ends of the windings L11 and L12 are respectively connected to the two ends of the functional resistor (1). The output ends of the windings L11 and L12 are respectively connected to the two ends of the first capacitor C11 in the LC-π circuit (3). The two ends of the second capacitor C12 in the LC-π circuit (3) are the output interface terminals of this filter.

2. The filter for externally connecting a DEH cabinet DC signal to a waveform recorder according to claim 1, wherein The designed filter satisfies the circuit board of the filter circuit (4) described in claim 1 and is adapted to the direct connection with the corresponding oscillograph and the DEH cabinet wire (5).

3. A filter applicable to the DC signal of the external DEH cabinet of the oscillograph, characterized in that, It further includes a filter housing. Inside the filter housing, a circuit board printed with the filter circuit (4) is installed. The two ends of the functional resistor (1) are respectively connected with screw spring pressing pieces (7) for connection with the DEH cabinet wire connection. The two ends of the second capacitor C12 are respectively connected with conductive copper rings (9) for connection with the oscillograph pen (6).

4. A filter applicable to the DC signal of the external DEH cabinet of the oscillograph, as described in claim 3, wherein, The surface of the filter housing is engraved with corresponding input and output engraved marks (8), and the marks are recessed from the surface of the filter housing.

5. A filter applicable to the DC signal of the external DEH cabinet of a recorder, characterized in that, The screw spring pressing pieces (7) and the conductive copper rings (9) are respectively installed on the left and right sides of the filter housing.

6. A filter applicable to the DC signal of the external DEH cabinet of the oscillograph, as claimed in claim 3, wherein The filter housing is installed through a snap design.

Images