Composite filter circuit

Abstract

The utility model relates to a composite filter circuit comprising a first line and a second line which are connected to a variable frequency power supply. The first circuit comprises a power transformer, a frequency converter, a motor and a variable-frequency power supply which are connected in sequence; the second line comprises a first filter used for higher harmonic filtering, a second filter used for electromagnetic interference filtering, an isolation transformer and electrical equipment. The variable frequency power source, the first filter, the second filter, the isolation transformer and the electrical equipment are connected in sequence. According to the utility model, through combination of the first filter and the second filter, high-frequency harmonic current with radiation energy and high-frequency harmonics during operation of a motor and electrical equipment in the circuit can be weakened, harmonic pollution is reduced, and the stability of the circuit is improved.

Description

Technical Field

[0001] This utility model relates to the field of frequency converter isolation and anti-interference technology, specifically to a composite filter circuit. Background Technology

[0002] During the operation of electrical equipment, the frequency converter in the circuit containing the electrical equipment will generate a variety of interference sources, such as input current, output voltage, and output current. Since the input current is a non-sinusoidal wave, it causes the waveform of the network voltage to be distorted, thereby interfering with the surrounding electrical equipment. The output voltage of the frequency converter is a high-frequency, high-voltage pulse wave, which interferes with the surrounding electrical equipment through the distributed capacitance between the lines. The output current contains high-order harmonic components with the same frequency as the carrier wave, and the electromagnetic waves generated will interfere with the normal operation of the surrounding electrical equipment.

[0003] In addition, there are numerous interference factors along the propagation path of the frequency converter, such as radiated interference, electromagnetic induction, and electrostatic induction. Furthermore, it should be noted that the electromagnetic interference (EMI) generated by the motors and machines themselves on the frequency converter is also a concern. Therefore, a single filtering method is no longer sufficient to ensure the normal operation of the affected equipment. Utility Model Content

[0004] To address the issue of diverse interference factors affecting frequency converters, this invention provides a composite filter circuit that improves filtering performance and filters and resists electromagnetic interference from the equipment's own motor and the machine during operation.

[0005] The technical objective of this utility model is achieved through the following technical solution:

[0006] A composite filter circuit includes a first line and a second line connected to a frequency converter power supply.

[0007] The first circuit includes a power transformer, a frequency converter, and a motor, with the frequency converter, power transformer, frequency converter, and motor connected in sequence.

[0008] The second line includes a first filter for high-order harmonic filtering, a second filter for electromagnetic interference filtering, an isolation transformer, and electrical equipment. The frequency converter, the first filter, the second filter, the isolation transformer, and the electrical equipment are connected in sequence.

[0009] Furthermore, the first filter is a π-type filter.

[0010] Furthermore, the second filter is an EMI filter.

[0011] Furthermore, the π-type filter includes capacitor C5, capacitor C6, and coil L3, with capacitor C6 and coil L3 connected in series and then connected in parallel with capacitor C5.

[0012] Furthermore, the EMI filter includes capacitors C1, C2, C3, and C4, coil L1, coil L2, and a resistor; capacitors C3 and C4 are connected in series and then in parallel with the resistor and capacitor C1; coil L1, capacitor C2, and coil L2 are connected in series and then in parallel with the series-connected capacitors C3 and C4; the resistor is connected in parallel with capacitor C6.

[0013] Furthermore, capacitors C1 and C2 are differential-mode capacitors with capacitance parameters ranging from 0.01uF to 0.47uF; capacitors C3 and C4 are common-mode capacitors with capacitance parameters ranging from 10nF to 47nF; and coils L1 and L2 are common-mode chokes with inductance parameters ranging from 3mH to 5mH.

[0014] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0015] This invention can reduce high-frequency harmonic currents with radiant energy and high-frequency harmonics in the operation of motors and electrical equipment in circuits by combining the first filter and the second filter.

[0016] In addition, preventing the leakage of internal harmonics generated in motors, electrical equipment and the entire circuit can significantly reduce harmonic pollution generated by equipment in the circuit, reduce the harm of harmonics to equipment, lines and personnel, improve the power factor of the power system, reduce power energy loss, improve the stability of the power system, reduce the distortion of power system voltage caused by harmonics, and protect the equipment.

[0017] Furthermore, the composite filter circuit of this application can effectively reduce losses caused by electromagnetic interference by setting a second filter, thereby reducing the operation and maintenance costs of the power system.

[0018] The composite filter circuit of this invention uses all electronic components and does not use digital components, and can be applied to ordinary circuits and high-voltage circuits. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the composite filter circuit connection in this utility model.

[0020] Figure 2 This is a schematic diagram of the first filter in this utility model.

[0021] Figure 3 This is a schematic diagram of the second filter in this utility model.

[0022] In the picture:

[0023] 1. Power transformer; 2. Frequency converter; 3. Motor; 4. First filter; 5. Second filter; 6. Isolation transformer; 7. Electrical equipment. Detailed Implementation

[0024] The technical solution of this utility model will be further described below with reference to specific embodiments:

[0025] A composite filter circuit includes a first line and a second line connected to a frequency converter power supply, such as... Figure 1 As shown:

[0026] The first circuit includes a power transformer 1, a frequency converter 2, and a motor 3, with the frequency converter, power transformer 1, frequency converter 2, and motor 3 connected in sequence.

[0027] The second circuit includes a first filter 4 for high-order harmonic filtering, a second filter 5 for electromagnetic interference filtering, an isolation transformer 6, and electrical equipment 7. Common electrical equipment, such as ballast water pumps and fire pumps on ships, are easily affected by harmonic interference, which can reduce pump operating efficiency and seriously affect ship safety. The frequency converter, the first filter 4, the second filter 5, the isolation transformer 6, and the electrical equipment 7 are connected in sequence. The second filter performs secondary filtering at the end of the first filter.

[0028] The first filter 4 is a π-type filter, and the second filter 5 is an EMI filter. The π-type filter installed at the front end of the electrical equipment 7 can attenuate high-frequency noise. Since the operation of the motor 3 in the first circuit will generate electromagnetic interference to the electrical equipment 7 in the second circuit, the EMI filter can attenuate the electromagnetic interference signal. Then, the first circuit and the second circuit are electrically isolated by the isolation transformer 6.

[0029] More specifically, the π-type filter is a π-type LC filter, such as... Figure 2 As shown, the π-type filter includes capacitor C5, capacitor C6 and coil L3. Capacitors C5 and C6 are filter capacitors, and coil L3 is a filter inductor. Capacitors C6 and coil L3 are connected in series and then connected in parallel with capacitor C5.

[0030] An EMI filter is a passive bidirectional network, connected to the power supply at one end and the load at the other. It primarily consists of capacitors and resistors. The combination of these components matches the system network impedance to attenuate electromagnetic interference signals and protect the operation of electrical equipment. Furthermore, the inductive section of the EMI filter functions as both a low-pass filter, allowing stable AC current flow, and a high-impedance filter, effectively filtering high-frequency signals.

[0031] like Figure 3As shown, the EMI filter includes capacitors C1, C2, C3, and C4, coils L1 and L2, and a resistor. Capacitors C3 and C4 are connected in series and then in parallel with the resistor and capacitor C1. Coils L1, C2, and L2 are connected in series and then in parallel with the series-connected capacitors C3 and C4. The resistor is connected in parallel with capacitor C6. Capacitors C1 and C2 are differential-mode capacitors with capacitance values ​​between 0.01uF and 0.47uF; capacitors C3 and C4 are common-mode capacitors with capacitance values ​​between 10nF and 47nF; the variable resistor has a maximum resistance of 1MΩ; coils L1 and L2 are common-mode chokes, which are coils wound in the same direction on a ferrite torsion ring, with inductance values ​​between 3mH and 5mH.

[0032] When a common-mode interference signal arrives, coils L1 and L2 will generate magnetic fields in the same direction, and coils L1 and L2 will generate a large impedance to attenuate the interference signal. For mode signals, the magnetic fields generated by coils L1 and L2 cancel each other out and do not affect the normal power signal transmission.

[0033] This embodiment is merely a further explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make non-inventive modifications to this embodiment as needed, but such modifications are protected by patent law as long as they fall within the scope of the claims of the present invention.

Claims

1. A composite filter circuit, characterized in that, This includes the first and second lines connected to the frequency converter power supply. The first line includes a power transformer, a frequency converter, and a motor, wherein the frequency converter, power transformer, frequency converter, and motor are connected in sequence; The second line includes a first filter for high-order harmonic filtering, a second filter for electromagnetic interference filtering, an isolation transformer, and electrical equipment, wherein the frequency converter, the first filter, the second filter, the isolation transformer, and the electrical equipment are connected in sequence.

2. The composite filter circuit according to claim 1, characterized in that, The first filter is a π-type filter.

3. A composite filter circuit according to claim 2, characterized in that, The second filter is an EMI filter.

4. A composite filter circuit according to claim 2, characterized in that, The π-type filter includes capacitor C5, capacitor C6 and coil L3, which are connected in series and then in parallel with capacitor C5.

5. A composite filter circuit according to claim 3, characterized in that, The EMI filter includes capacitors C1, C2, C3, and C4, coils L1 and L2, and a resistor. Capacitors C3 and C4 are connected in series and then in parallel with the resistor and capacitor C1. Coils L1, C2, and L2 are connected in series and then in parallel with the series-connected capacitors C3 and C4. The resistor is connected in parallel with capacitor C6.

6. A composite filter circuit according to claim 5, characterized in that, The capacitors C1 and C2 are differential mode capacitors with capacitance parameters ranging from 0.01uF to 0.47uF; the capacitors C3 and C4 are common mode capacitors with capacitance parameters ranging from 10nF to 47nF; the coils L1 and L2 are common mode chokes with inductance parameters ranging from 3mH to 5mH.

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