High-power variable frequency equipment distribution box and residual current protection device

Abstract

The application relates to the technical field of residual current protection, in particular to a high-power variable-frequency equipment distribution box and a residual current protection device, which comprises a residual current transformer for collecting residual current, the core of the residual current transformer comprises a plurality of sensing units which are arranged in sequence, the sensing unit comprises a first annular sheet body and two second annular sheet bodies which are arranged on the first annular sheet body, the first annular sheet body is a 1J85 material metal sheet, and the second annular sheet bodies are silicon steel metal sheets; and a controller connected with the residual current transformer, which is used for acquiring the residual current, and forms a disconnecting signal to control the corresponding circuit to be disconnected to realize protection when the residual current is greater than 30 mA or the duration is greater than 0.1 S. The harmonic interference signal in the output signal of the residual current transformer has been greatly reduced, and the filtering function of the harmonic interference signal is realized.

Description

Technical Field

[0001] This invention relates to the field of residual current protection technology, and specifically to a power distribution box and residual current protection device for high-power frequency converter equipment. Background Technology

[0002] According to domestic and international standards such as GB / T 13870.1-2022 and IEC 60479-1:2018, when the residual current value is ≤30mA and the duration is ≤0.1S, the personal safety of operators can be guaranteed. This is also the setting parameter requirement for the end residual current protection device. With the widespread application of high-power frequency converters in building construction, the output voltage of the frequency converter adopts PWM modulation technology, which will form a high-frequency charging and discharging circuit (harmonic circuit) between the motor cable and the ground. The charging and discharging current flows back to the power supply end through the PE line, generating leakage current. At the same time, the distributed capacitance between the motor winding and the ground will also generate capacitive leakage current. The corresponding residual current protection device with ≤30mA / 0.1S in the distribution box often malfunctions, seriously affecting the normal use of high-power frequency converters. Based on the above situation, inverters from well-known domestic and foreign brands currently require the protection threshold of the residual current device to be set to 200mA / 0.1S to avoid frequent malfunctions affecting the normal operation of the load equipment. However, this seriously exceeds the national standard of 30mA / 0.1S, making it difficult to guarantee the personal safety of on-site construction personnel. Summary of the Invention

[0003] The purpose of this invention is to overcome the defects of the prior art and provide a power distribution box and residual current protection device for high-power frequency converters, thereby solving the problem that existing high-power frequency converters often malfunction due to harmonic interference, affecting the normal use of the equipment.

[0004] The technical solution to achieve the above objectives is:

[0005] This invention provides a residual current protection device, comprising:

[0006] A residual current transformer is used to collect residual current. The core of the residual current transformer includes multiple sensing units stacked in sequence. Each sensing unit includes a first annular sheet and two second annular sheets stacked on the first annular sheet. The first annular sheet is a 1J85 material metal sheet, and the second annular sheet is a silicon steel metal sheet.

[0007] The controller connected to the residual current transformer is used to acquire the residual current, and when the residual current is greater than 30mA or the duration is greater than 0.1S, it generates a disconnect signal to control the corresponding circuit to disconnect and achieve protection.

[0008] A further improvement of the residual current protection device of the present invention is that the first annular plate and the second annular plate have the same size.

[0009] A further improvement of the residual current protection device of the present invention is that the outer contours of the first annular plate and the second annular plate are elliptical.

[0010] A further improvement of the residual current protection device of the present invention is that it further includes a low-pass filter, which is connected between the residual current transformer and the controller.

[0011] A further improvement of the residual current protection device of the present invention is that the controller includes a harmonic analysis module and a harmonic total quantity calculation module;

[0012] The total harmonic calculation module is used to calculate the total effective value of harmonics;

[0013] The harmonic analysis module is connected to the total harmonic calculation module. The harmonic analysis module is used to perform harmonic analysis on the main circuit current and residual current passing through the residual current transformer to improve the accuracy of the residual current. The harmonic analysis is performed up to 98% of the total effective value of the harmonics.

[0014] A further improvement of the residual current protection device of the present invention is that the frequency of the main circuit current passing through the residual current transformer is 50Hz or 60Hz.

[0015] The present invention also provides a high-power frequency converter distribution box, comprising:

[0016] Box;

[0017] A residual current protection device is installed inside the enclosure;

[0018] The main circuit is located inside the enclosure, and the phase and neutral lines of the main circuit pass through the core of the residual current transformer.

[0019] A further improvement of the high-power frequency converter distribution box of the present invention is that the outer side of the box is provided with an outer shell, which is a fully enclosed metal shell with a protection level of IP44.

[0020] A further improvement of the high-power frequency converter distribution box of the present invention is that the grounding resistance of the box body is within 4Ω.

[0021] The beneficial effects of the high-power frequency converter distribution box and residual current protection device of the present invention are as follows:

[0022] The residual current protection device of the present invention employs a stacked induction unit, including a first annular plate and two second annular plates. The combination of the first and second annular plates improves the effective permeability and pulse permeability. It can accurately sense currents with an operating frequency of 50Hz or 60Hz, while for mid-to-high frequency harmonic currents exceeding these frequencies, the magnetic induction of the transformer core will drop sharply. Thus, the harmonic interference signal in the output signal of the residual current transformer has been greatly reduced, achieving the function of filtering harmonic interference signals.

[0023] The residual current transformer of the present invention, through its structural design, can effectively filter harmonics caused by high-frequency charging and discharging circuits and distributed capacitance, thereby significantly reducing the impact of frequency conversion equipment on residual current measurement.

[0024] The low-pass filter provided in this invention is used to prevent harmonic interference signals contained in the limit signal of the residual current transformer connected to the digital circuit from affecting the normal operation of the digital circuit.

[0025] The harmonic analysis module of this invention can cover 98% of the harmonic proportion, avoiding the problem that harmonic analysis will fail when the high frequency harmonic content is high due to a fixed number of harmonic analysis. The accuracy of the fundamental residual current value decomposed by harmonic analysis can meet the judgment of 30mA pre-set, and will not cause false operation due to harmonic interference. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the core structure of the residual current transformer in the residual current protection device of the present invention.

[0027] Figure 2 This is a system block diagram of the residual current protection device of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] See Figure 1 This invention provides a power distribution box and residual current protection device for a high-power frequency converter. It utilizes a high-pulse magnetic permeability material (i.e., 1J85 (permalloy) material) and reduces interference leakage current from the high-frequency charging and discharging circuit through core output filtering. It effectively filters harmonics caused by the high-frequency charging and discharging circuit and distributed capacitance, significantly reducing the impact of the frequency converter on residual current measurement. The power distribution box and residual current protection device of this invention are described below with reference to the accompanying drawings.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0031] See Figure 1This diagram shows a schematic representation of the core structure of the residual current transformer in the residual current protection device of the present invention. (See also...) Figure 2 The diagram shows a system block diagram of the residual current protection device of the present invention. The following is in conjunction with... Figure 1 and Figure 2 The present invention describes the combined support structure for the foundation pit.

[0032] like Figure 1 and Figure 2 As shown, the residual current protection device of the present invention includes a residual current transformer 21 and a controller 22. The residual current transformer 21 is used to collect residual current. The iron core 211 of the residual current transformer 21 includes a plurality of sensing units stacked in sequence. The sensing unit includes a first annular plate and two second annular plates stacked on the first annular plate. The first annular plate is a 1J85 material metal sheet, and the second annular plate is a silicon steel metal sheet. The controller 22 is connected to the residual current transformer 21. The controller 22 is used to acquire the residual current and judge the magnitude of the residual current. When the residual current is greater than 30mA or the duration is greater than 0.1S, a disconnection signal is generated to control the corresponding circuit to disconnect and realize protection.

[0033] Preferably, the controller 22 is connected to the circuit breaker control of the circuit. When it is determined that the residual current is greater than 30mA or the duration is greater than 0.1S, the controller sends the resulting disconnect signal to the circuit breaker so that the circuit breaker can perform disconnect protection.

[0034] In one specific embodiment of the present invention, the first annular sheet and the second annular sheet have the same dimensions.

[0035] Furthermore, the outer contours of the first and second annular pieces are elliptical. The first and second annular pieces are generally racetrack-shaped, with elliptical hollow regions formed inside.

[0036] The core 211 of the residual current transformer 21 is formed by overlapping and pressing multiple independent metal sheets (including 1J85 material metal sheets and silicon steel metal sheets). The core 211 is uniformly wound with windings and connected to the detection circuit.

[0037] The residual current transformer 21 of the present invention has an iron core 211 formed by overlapping and pressing multiple metal sheets. It can accurately sense power frequency (50 / 60Hz) current and output it on the secondary side. For harmonic currents (medium and high frequency harmonic currents) exceeding this frequency, the magnetic induction of the iron core 211 will drop sharply. In this way, the harmonic interference signal in the output signal of the residual current transformer has been greatly reduced, realizing the filtering function of harmonic interference signal.

[0038] In one specific embodiment of the present invention, the residual current protection device further includes a low-pass filter connected between the residual current transformer and the controller.

[0039] The function of a low-pass filter is to isolate the signal from the residual current transformer connected to the digital circuit through an optocoupler before inputting it into the main circuit of the digital circuit, so as to prevent harmonic interference signals contained in the signal from the residual current transformer connected to the digital circuit from affecting the normal operation of the digital circuit.

[0040] By using a low-pass filter in conjunction with a residual current transformer 21, low, medium and high frequency harmonics can be filtered out, thereby improving the accuracy of residual current detection.

[0041] In one specific embodiment of the present invention, the controller includes a harmonic analysis module and a harmonic total calculation module; the harmonic total calculation module is used to calculate the total effective value of harmonics.

[0042] The harmonic analysis module is connected to the total harmonic calculation module. The harmonic analysis module is used to perform harmonic analysis on the main circuit current and residual current passing through the residual current transformer to improve the accuracy of the residual current. The harmonic analysis is performed up to 98% of the total effective value of the harmonics.

[0043] The harmonic analysis module of this invention uses Fast Fourier Transform (FFT) to perform harmonic analysis on the main circuit current and the residual current to obtain the fundamental and harmonic components. Then, the fundamental component is extracted to filter out the harmonics, thereby improving the accuracy of the residual current.

[0044] The total effective value of harmonics is a variable value. The total harmonics calculation module calculates the true effective value of the waveform, then calculates the effective value of the fundamental wave, and finally calculates the square root of the difference between the two to obtain the total effective value of the harmonics.

[0045] The main circuit current can be directly measured by the switch, and the residual current can be measured by the residual current transformer. The harmonic analysis module performs harmonic analysis on the main circuit current and the residual current. The harmonic analysis is used to decompose the harmonics, that is, to obtain the harmonics by fast Fourier series decomposition. The harmonic analysis module decomposes the total harmonic quantity up to the nth harmonic through fast Fourier series decomposition (which is less than the total effective value of the current harmonics). When the total harmonic quantity up to the nth harmonic measured by the decomposition of the harmonics is not less than the total effective value of the current harmonics or 98% of the total amount, the decomposition of the next harmonic is not continued.

[0046] The harmonic total calculation module of this invention can calculate the total harmonics based on the actual situation, and then ensure that the number of harmonic analyses reaches 98% of the actual total, avoiding the problem of failure when the fixed number of harmonic analyses is high in high-frequency harmonics. This invention performs harmonic analysis on the main circuit current and residual current, with the number of harmonic analyses limited to 98% of the total harmonic content. The accuracy of the decomposed fundamental residual current value meets the effective judgment of the 30mA threshold, preventing malfunctions due to harmonic interference.

[0047] In one specific embodiment of the present invention, when the residual current protection device of the present invention is in use, the phase line and the center line of the main circuit current pass through the hollow area of ​​the residual current transformer, and the frequency of the main circuit current passing through the residual current transformer is preferably 50Hz or 60Hz.

[0048] The present invention also provides a power distribution box for a high-power frequency converter, the structure of which will be described below.

[0049] The high-power frequency converter distribution box of the present invention includes a box body, a residual current protection device and a main circuit; the residual current protection device is located inside the box body, and the main circuit is also located inside the box body, wherein the phase line and neutral line of the main circuit pass through the iron core of the residual current transformer.

[0050] Furthermore, the outer side of the enclosure is provided with a shell, which is a fully enclosed metal shell with an IP44 protection rating.

[0051] Furthermore, the grounding resistance of the enclosure is within 4Ω.

[0052] With a fully enclosed metal casing that achieves an IP44 protection rating and a grounding resistance of less than 4Ω, the electromagnetic interference generated by the frequency converter in the surrounding space can be effectively shielded, preventing the residual current protection device from malfunctioning due to electromagnetic interference in the space.

[0053] Currently used residual current protection devices for high-power frequency converter equipment distribution boxes, designed to prevent malfunctions, can cause false tripping due to excessively high proportions of harmonic current / voltage in the circuit. This hinders their widespread application in high-power frequency converter equipment circuits.

[0054] 1. Existing technical solutions include adding a high-pass filter circuit, but due to the magnetic saturation condition of the filter system, the expected filtering function cannot be achieved when the proportion of harmonics is too large.

[0055] 2. Existing technical solutions can reduce the impact of harmonics on residual current detection and judgment under certain operating conditions by separately detecting the residual current of the fundamental wave and the nth harmonic, and by decomposing the residual current into the fundamental wave and the nth harmonic through the algorithm. However, when the high-frequency harmonics account for a large proportion of the residual current, the residual current of the nth harmonic decomposed by the algorithm may still exceed the 30mA threshold, leading to false operation.

[0056] The present invention, through the design of the residual current transformer core, ensures that there is no risk of magnetic saturation due to the increase in power of the frequency converter. The residual current transformer can significantly reduce harmonic interference signals, effectively filter harmonics caused by high-frequency charging and discharging circuits and distributed capacitance, and greatly reduce the impact of frequency converter on residual current measurement.

[0057] The low-pass filter provided in this invention is used to prevent harmonic interference signals contained in the limit signal of the residual current transformer connected to the digital circuit from affecting the normal operation of the digital circuit.

[0058] The harmonic analysis module of this invention can cover 98% of the harmonic proportion, avoiding the problem that harmonic analysis will fail when the high frequency harmonic content is high due to a fixed number of harmonic analysis. The accuracy of the fundamental residual current value decomposed by harmonic analysis can meet the judgment of 30mA pre-set, and will not cause false operation due to harmonic interference.

[0059] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A residual current protection device, characterized in that, include: A residual current transformer is used to collect residual current. The core of the residual current transformer includes multiple sensing units stacked in sequence. Each sensing unit includes a first annular sheet and two second annular sheets stacked on the first annular sheet. The first annular sheet is a 1J85 material metal sheet, and the second annular sheet is a silicon steel metal sheet. The controller connected to the residual current transformer is used to acquire the residual current, and when the residual current is greater than 30mA or the duration is greater than 0.1S, it generates a disconnect signal to control the corresponding circuit to disconnect and achieve protection.

2. The residual current protection device as described in claim 1, characterized in that, The first annular sheet and the second annular sheet have the same dimensions.

3. The residual current protection device as described in claim 1, characterized in that, The outer contours of the first annular sheet and the second annular sheet are elliptical.

4. The residual current protection device as described in claim 1, characterized in that, It also includes a low-pass filter connected between the residual current transformer and the controller.

5. The residual current protection device as described in claim 1, characterized in that, The controller includes a harmonic analysis module and a harmonic total calculation module; The total harmonic calculation module is used to calculate the total effective value of harmonics; The harmonic analysis module is connected to the total harmonic calculation module. The harmonic analysis module is used to perform harmonic analysis on the main circuit current and residual current passing through the residual current transformer to improve the accuracy of the residual current. The harmonic analysis is performed up to 98% of the total effective value of the harmonics.

6. The residual current protection device as described in claim 1, characterized in that, The frequency of the main circuit current passing through the residual current transformer is 50Hz or 60Hz.

7. A power distribution box for a high-power frequency converter, characterized in that, include: Box; The residual current protection device as described in any one of claims 1 to 6 is provided inside the enclosure; The main circuit is located inside the enclosure, and the phase and neutral lines of the main circuit pass through the core of the residual current transformer.

8. The high-power frequency converter distribution box as described in claim 7, characterized in that, The outer side of the enclosure is provided with a shell, which is a fully enclosed metal shell with a protection level of IP44.

9. The high-power frequency converter distribution box as described in claim 7, characterized in that, The grounding resistance of the enclosure is within 4Ω.

Images