Low-voltage distribution circuit and distribution box for uninterruptible power maintenance

Abstract

The utility model relates to the technical field of low-voltage power distribution, and discloses a low-voltage power distribution circuit and a power distribution box for uninterruptible power maintenance, the circuit comprises a main incoming line switch circuit breaker, a main busbar, a plurality of branch switch circuit breakers with different rated currents, a zero line busbar and a ground wire busbar; the main incoming line switch circuit breaker is electrically connected to a low-voltage power supply system, the main busbar is electrically connected to the main incoming line switch circuit breaker, the plurality of branch switch circuit breakers are electrically connected to the main busbar, a zero line access end of each branch switch circuit breaker is connected with the zero line busbar, a ground line access end of each branch switch circuit breaker is connected with the ground line busbar, and the main incoming line switch circuit breaker is electrically connected with the main busbar. The confluence end of the zero line busbar is connected with a zero line of the low-voltage power supply system, and the confluence end of the ground line busbar is connected with a ground line of the low-voltage power supply system. Compared with the prior art, the circuit provided by the utility model can directly select the output mode of the corresponding output unit to adjust the impedance load or replace the shunt without interrupting the total power, and is safe and reliable in structure and convenient to operate.

Description

Technical Field

[0001] The utility model belongs to the technical field of low-voltage power distribution, in particular to a low-voltage power distribution circuit and a distribution box for uninterrupted power supply maintenance. Background Art

[0002] With the advancement of industrial technology, distribution boxes are increasingly used in low-voltage power supply systems. Based on the principle of centralized control lines, the demand for distribution boxes in machining workshops is increasing. Generally speaking, distribution boxes mainly play the role of distributing electrical energy and controlling the power supply of equipment in the workshop. Therefore, whether the design of the low-voltage distribution box and its internal distribution circuit is reasonable will directly affect the operating reliability of the production equipment in the entire workshop.

[0003] Traditional distribution boxes have the following problems:

[0004] 1. The internal circuit planning is poor and the integration level is low, resulting in the large space occupied by the entire electrical box.

[0005] 2. The internal circuit nodes are numerous and complex, making installation and wiring difficult, and the safety and reliability are poor.

[0006] 3. Generally, live maintenance is not allowed. If you need to replace the branch circuit load in the distribution box or dismantle the branch switch on the branch, you need to turn off the main switch of the distribution box and then sort out the internal lines of the distribution box. This will seriously affect the production of the workshop and increase the cost of the workshop production. Utility Model Content

[0007] The utility model provides a low-voltage power distribution circuit and a power distribution box for non-stop power-on maintenance, which are used to solve the problems existing in the prior art.

[0008] In the first aspect, in order to achieve the above-mentioned purpose, the utility model provides the following technical solutions:

[0009] A low-voltage power distribution circuit for non-stop power supply maintenance comprises a main incoming line switch circuit breaker, a main bus, a plurality of branch switch circuit breakers with different rated currents, a neutral bus and a ground bus; the main incoming line switch circuit breaker is electrically connected to a low-voltage power supply system, the main bus is electrically connected to the main incoming line switch circuit breaker, a plurality of branch switch circuit breakers are respectively electrically connected to the main bus, a neutral line access end of each branch switch circuit breaker is connected to the neutral bus, a ground line access end of each branch switch circuit breaker is connected to the ground bus, a bus end of the neutral bus is connected to a neutral line of a low-voltage power supply system, and a bus end of the ground bus is connected to a ground line of the low-voltage power supply system;

[0010] Among them, the three-phase power supply access ends of the main bus are respectively connected to the three-phase power supply output ends corresponding to the main incoming line switch circuit breaker; the main bus is built with a phase line input bar for connecting the corresponding three-phase power supply access ends and a phase line output bar electrically isolated from the phase line input bar, and a head end selection output unit, a plurality of middle selection output units and a terminal selection output unit are arranged between the phase line input bar and the phase line output bar, the input end of the head end selection output unit is connected to the phase line input bar, and the first selection output end of the head end selection output unit is connected to the phase line output bar; the first selection output end of the middle selection output unit is connected to the phase line output bar, and the input end of the middle selection output unit is connected to the second selection output end of the head end selection output unit or the second selection output end of the middle selection output unit of the previous level; the input end of the terminal selection output unit is connected to the second selection output end of the middle selection output unit of the last level, and the output end of the terminal selection output unit is connected to the phase line output bar; the branch switch circuit breaker is connected to the phase line output bar.

[0011] Through the above technical solution, each phase current output of the main bus is configured with a pair of phase line input bus and phase line output bus, and the phase line input bus and the phase line output bus are selectively connected through the head end selection output unit, multiple middle selection output units and terminal selection output units. Compared with the prior art, if it is necessary to replace the circuit load in the distribution box or disassemble the branch, there is no need to turn off the main incoming line switch circuit breaker, and the output mode of the corresponding output unit can be directly selected to realize live operation. This circuit structure is safe and reliable, easy to operate, fast to disassemble and assemble branches, no need to frequently organize the electrical box line, and modularization is realized. It can be widely used in low-voltage power supply networks of various optoelectronic industries. The normal production of the workshop will not be affected during the live operation process, which is conducive to reducing the production cost of the workshop. In addition, the circuit of the utility model mostly adopts a bus for unified convergence, replacing the traditional junction box or terminal block. The overall circuit has a high degree of integration, the line occupies a small space, and the line is simple to organize.

[0012] Preferably, the head-end selection output unit includes a single-contact main switch, a head-end slot electrically isolating the input end from the output end, a head-end resistor and a head-end double-contact switch. One end of the single-contact main switch is connected to the phase line input row, and the other end is connected in series with the head-end slot and the head-end double-contact switch. The first selection output end of the head-end double-contact switch is connected to the phase line output row, and the second selection output end of the head-end double-contact switch is connected to the input end of the middle selection output unit. The head-end resistor is removably electrically bridged to the head-end slot.

[0013] Specifically, the middle selection output unit includes a middle card slot with an input end electrically isolated from an output end, a middle double-contact switch and a middle resistor, the input end of the middle card slot is connected to the second selection output end of the head-end selection output unit or the second selection output end of the middle selection output unit of the previous level, the output end of the middle card slot is connected in series with the middle double-contact switch, the first selection output end of the middle double-contact switch is connected to the phase line output row, the second selection output end of the middle double-contact switch is connected to the input end of the terminal selection output unit or the input end of the middle selection output unit of the next level, and the middle resistor is detachably electrically connected across the middle card slot;

[0014] The terminal selection output unit includes a terminal card slot with an input end and an output end electrically isolated, a terminal single-contact switch and a terminal impedance device. The input end of the terminal card slot is connected to the second selection output end of the last-stage middle selection output unit, and the output end of the terminal card slot is connected in series with the terminal single-contact switch and then connected to the phase line output row; the terminal impedance device is detachably electrically connected to the terminal card slot;

[0015] The three-phase power supply access terminals of the main incoming line switch circuit breaker are respectively connected to the corresponding phase lines of the low-voltage power supply system, the neutral line access terminal of the main incoming line switch circuit breaker is connected to the neutral line of the low-voltage power supply system, and the ground line access terminal of the main incoming line switch circuit breaker is connected to the ground line of the low-voltage power supply system.

[0016] Preferably, both the main incoming line switch circuit breaker and the branch switch circuit breaker are MCCB circuit breakers.

[0017] Preferably, the main incoming line switch circuit breaker uses a switch circuit breaker with a rated current of 1000A-1500A, and the multiple branch switch circuit breakers use switch circuit breakers with a rated current of 15A-800A.

[0018] Preferably, it also includes an instrument indicating unit, which is electrically connected to the three-phase phase line output bus in the main bus.

[0019] Preferably, the power supply access end of the branch switch circuit breaker is provided with an insulating protective layer.

[0020] Preferably, the main busbar is a copper busbar.

[0021] In the second aspect, in order to achieve the above-mentioned purpose, the utility model provides the following technical solutions:

[0022] A distribution box comprises a box body and a box door. The box body is installed with the above-mentioned low-voltage distribution circuit for non-stop maintenance. The outer side of the box door is provided with an instrument display screen and indicator lights. The box door is movably connected to the box body.

[0023] Through the above technical solution, the circuit structure of the utility model adopts the design of plugging branch switch circuit breakers on both sides of the middle bus, the circuit integration degree is high, there is no redundant wire occupying the space in the box, and the box design volume requirement is relatively small.

[0024] The beneficial effects of the utility model are:

[0025] 1. Compared with the prior art, if it is necessary to replace the circuit load in the distribution box or disassemble the branch, the circuit of the utility model does not need to turn off the main incoming line switch circuit breaker, and directly selects the output mode of the corresponding output unit to realize live operation. This circuit structure is safe and reliable, easy to operate and can be widely used in low-voltage power supply networks of various optoelectronic industries. The live operation process will not affect the normal production of the workshop, which is conducive to reducing the production cost of the workshop.

[0026] 2. Compared with the prior art, when the load of the circuit of the utility model needs to be changed, it is only necessary to plug and unplug the resistor in the corresponding slot without powering off.

[0027] 3. Compared with the prior art, the internal circuit integration degree of the electric box of the utility model is high, and the design volume of the electric box itself is small, which can save space in the workshop. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a connection diagram of a low-voltage power distribution circuit for non-stop power-on maintenance in Embodiment 1 of the present utility model;

[0029] Figure 2 It is a connection diagram of the phase line input row and the phase line output row corresponding to the main bus A in the first embodiment of the present utility model;

[0030] Figure 3 It is a schematic diagram of providing an insulating protective layer for a branch switch circuit breaker in Embodiment 1 of the present utility model;

[0031] Figure 4 It is a simplified connection diagram of the main bus and the branch switch circuit breaker in the first embodiment of the utility model;

[0032] Figure 5 It is a wiring diagram of the instrument indicating unit in the first embodiment of the utility model;

[0033] Figure 6 It is a structural schematic diagram of the distribution box in the second embodiment of the utility model.

[0034] Description of reference numerals:

[0035] 1. Main incoming line switch circuit breaker; 2. Main bus; 3. Branch switch circuit breaker; 4. Neutral bus; 5. Ground bus; 21. Phase input bus; 22. Phase output bus; 23. Head end selection output unit; 24. Middle selection output unit; 25. End selection output unit; 100. Box door; 101. Instrument display screen; 102. Indicator light. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all of the embodiments; based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0037] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0038] The utility model discloses a low-voltage power distribution circuit and a power distribution box for non-stop power-on maintenance, which are used to solve the problems existing in the prior art.

[0039] Embodiment 1

[0040] Reference Figure 1 In this embodiment, the low-voltage power distribution circuit used for non-stop maintenance includes a main incoming line switch circuit breaker 1, a main bus 2, a plurality of branch switch circuit breakers 3 with different rated currents, a neutral bus 4 and a ground bus 5.

[0041] Specifically, the main incoming switch circuit breaker 1 is electrically connected to the low-voltage power supply system and is used to receive the electric energy of the low-voltage power supply system. The main incoming switch circuit breaker 1 serves as a main circuit breaker. In this embodiment, the main bus 2 is a dedicated copper bus, which is provided with a plurality of input and output terminals that are spaced apart from each other and electrically isolated. The main bus 2 is electrically connected to the main incoming switch circuit breaker 1, and a plurality of branch switch circuit breakers 3 are electrically connected to the main bus 2 respectively. The neutral line access end of each branch switch circuit breaker 3 is connected to the neutral line bus 4, and the ground line access end of each branch switch circuit breaker 3 is connected to the ground line bus 5. The bus end of the neutral line bus 4 is connected to the neutral line of the low-voltage power supply system, and the bus end of the ground line bus 5 is connected to the ground line of the low-voltage power supply system.

[0042] Compared with the prior art, the circuit of the utility model achieves a higher degree of integration, is easy to maintain, safe and reliable, and is convenient for disassembly and assembly.

[0043] Among them, the three-phase power supply access terminal of the main incoming line switch circuit breaker 1 is respectively connected to the A, B, and C phases of the low-voltage power supply system, the neutral line access terminal of the main incoming line switch circuit breaker 1 is connected to the neutral line of the low-voltage power supply system, and the ground line access terminal of the main incoming line switch circuit breaker 1 is connected to the ground line of the low-voltage power supply system. The three-phase power supply access terminals of the above-mentioned main bus 2 are respectively connected to the three-phase power supply output terminals corresponding to the main incoming line switch circuit breaker 1 to receive the electric energy output by the main incoming line switch circuit breaker 1. The main bus 2 is built with a phase line input bus 21 and a phase line output bus 22, and the three phases A, B, and C of the main bus 2 are respectively equipped with a set of phase line input bus 21 and phase line output bus 22. The phase line input bus 21 is connected to the corresponding three-phase power supply access terminal, and the phase line input bus 21 and the phase line output bus 22 are electrically isolated in the initial state. A head-end selection output unit 23, a plurality of middle selection output units 24 and a terminal selection output unit 25 are arranged between the phase line input row 21 and the phase line output row 22. The input end of the head-end selection output unit 23 is connected to the phase line input row 21, and the first selection output end of the head-end selection output unit 23 is connected to the phase line output row 22. The first selection output end of the middle selection output unit 24 is connected to the phase line output row 22, and the input end of the middle selection output unit 24 is connected to the second selection output end of the head-end selection output unit 23 or the second selection output end of the middle selection output unit 24 of the previous stage. The input end of the terminal selection output unit 25 is connected to the second selection output end of the middle selection output unit 24 of the last stage, and the output end of the terminal selection output unit 25 is connected to the phase line output row 22. The branch switch circuit breaker 3 is connected to the phase line output row 22.

[0044] Through the above technical scheme, the phase line input bus 21 and the phase line output bus 22 are selectively connected through the head-end selection output unit 23, multiple middle selection output units 24 and the terminal selection output unit 25. Compared with the prior art, if it is necessary to replace the loop load in the distribution box or disassemble the branch, there is no need to turn off the main incoming line switch circuit breaker 1. The output mode of the corresponding output unit can be directly selected to realize the main power operation. This circuit structure does not require a reserved branch switch, and is safe, reliable, easy to operate and can be widely used in low-voltage power supply networks of various optoelectronic industries. The normal production of the workshop will not be affected during the live operation, which is conducive to reducing the production cost of the workshop.

[0045] Specifically, Figure 2 As shown, taking phase A of the main bus 2 as an example, the head-end selection output unit 23 includes a single-contact main switch, a head-end slot electrically isolating the input end from the output end, a head-end resistor and a head-end double-contact switch, the middle selection output unit 24 includes a middle slot electrically isolating the input end from the output end, a middle double-contact switch and a middle resistor, and the end selection output unit 25 includes an end slot electrically isolating the input end from the output end, a end single-contact switch and an end resistor.

[0046] For the head-end selection output unit 23, one end of its single-contact main switch is connected to the phase line input row 21, and the other end is connected in series to the head-end slot and the head-end double-contact switch. The first selection output end of the head-end double-contact switch is connected to the phase line output row 22, and the second selection output end of the head-end double-contact switch is connected to the input end of the middle slot. The head-end resistor is detachably electrically bridged to the head-end slot. When the head-end slot is inserted into the head-end slot, the single-contact main switch is closed and the first contact of the head-end double-contact switch is closed, the head-end selection output unit 23 outputs current to the phase line output row 22 with the first selection output end.

[0047] For the middle selection output unit 24, the input end of the middle card slot is connected to the second contact of the head end double contact switch or the second contact of the middle double contact switch in the middle selection output unit 24 of the previous stage, the output end of the middle card slot is connected in series with the middle double contact switch, the first contact of the middle double contact switch is connected to the phase line output row 22, the second contact of the middle double contact switch is connected to the input end of the end card slot or the input end of the middle selection output unit 24 of the next stage, and the middle resistor is detachably electrically connected to the middle card slot. When the head end card slot is inserted into the head end card slot, the single contact main switch is closed, the second contact of the head end double contact switch is closed, and the first contact of the middle double contact switch is closed, the head end selection output unit 23 and the middle selection output unit 24 are connected in series, and the phase line output row 22 is energized.

[0048] For the terminal selection output unit 25, the input end of the terminal slot is connected to the second selection output end of the last middle selection output unit 24, and the output end of the terminal slot is connected in series with the terminal single-contact switch and then connected to the phase line output row 22. The terminal impedance is detachably connected across the terminal slot. When the head-end slot is inserted into the head-end slot, the single-contact main switch is closed, the second contact of the head-end double-contact switch is closed, the second contact of the upper middle selection output unit 24 is closed, and the terminal single-contact switch is closed, the head-end selection output unit 23, the middle selection output unit 24 and the terminal selection output unit 25 are connected in series and turned on, and the phase line output row 22 is energized.

[0049] Based on the above circuit structure design, the total power load can be continuously expanded. Only by plugging and unplugging the middle resistor in the corresponding card slot, the load of the main bus 2 can be flexibly adjusted. The shape and structure of the above-mentioned head slot, middle slot and end slot are consistent, and the difference is that the current range that can be carried is different. The rated current range of the above-mentioned various slots is 15A-800A, which is designed according to actual conditions. The shape and structure of the above-mentioned head end resistor, middle resistor and end resistor are consistent. A fixed card is provided at the bottom of each resistor to connect the corresponding slot. The difference is that the threshold current that the resistors of different slots can carry is different. The threshold current range of the resistor is 1A, 5A, 10A, 20A, 50A, 100A, 125A, 250A, 400A, 600A, which needs to be selected and adjusted according to actual conditions.

[0050] In this embodiment, each phase of the main bus 2 is equipped with 5 slots, namely 1 head slot, 3 middle slots and 1 end slot. These 5 slots are centrally arranged on a matching base. In other embodiments, the number of slots is not limited, and is specifically designed according to the complexity of the power supply of the workshop. In this embodiment, each phase base of the main bus 2 can carry up to 5 impedance devices at the same time. Compared with the traditional distribution box, the current size can be adjusted to quickly change the switch size when the load changes, which will not affect production and greatly reduce the damage to the load caused by the current being too small or too large on the electrical equipment.

[0051] like Figure 3 As shown, the power access end (three-phase socket) of the branch switch circuit breaker 3 is provided with an insulating protective layer, which is used to improve the protection level of the socket of the main bus 2, that is, to achieve leakage protection to prevent accidental touch by personnel and tools, further improving the safety of the utility model.

[0052] like Figure 1 and Figure 4 As shown, in this embodiment, the main incoming line switch circuit breaker 1 uses an MCCB circuit breaker with a rated current of 1200A, and multiple branch switch circuit breakers 3 use MCCB circuit breakers with a rated current of 15A-800A. The branch switch circuit breaker 3 can use 1P, 2P or 3P circuit breakers, which can be selected according to actual needs.

[0053] In this embodiment, each of the branch switch circuit breakers 3 of 1P 15A, 2P 25A, 3P 100A, 3P 250A, 3P 400A, 3P 630A and 3P 800A selects a corresponding terminal of the phase output bar 22 connected to the main bus 2.

[0054] like Figure 5 As shown, the circuit of the utility model further comprises an instrument indicating unit, which is electrically connected to the phase line output ends of the three phases in the main bus 2.

[0055] Specifically, the instrument indicating unit may be DM2365S, which is used to monitor the A, B, and C three-phase output voltage and output current of the main bus 2.

[0056] The principle of the utility model circuit is:

[0057] by Figure 2For example, the impedance device is plug-in installed on the corresponding card slot, and its main function is to control current and voltage. The size of the impedance device is a standard uniform size, and the selection of its impedance value can be customized according to the size of the actual switch used. Different sizes refer to the actual impedance device color ring or actual indication size. When disassembling and assembling the branches of the practical circuit, it should be noted that a 5-hole plug-in box (with 5 built-in card slots) is provided for each of the three phases A, B, and C, located between the phase line input row 21 and the phase line output row 22 of the corresponding phase. Taking the card slots of phase A as an example, the corresponding card slots are numbered 1#-5#, respectively. When the 1# card slot is connected to meet the changed current value requirements, the 2#-5# card slots are empty and no impedance is connected. When the 2# card slot is connected to the impedance, the right paddle of the first end double-contact switch (i.e., S2) is connected downward, the 1# card slot is connected in series with the 2# card slot, and the 3#-5# card slots are not connected to the impedance. When the 3 card slot is connected to the impedance, the middle double-contact switch (i.e., S3) matching the 2# card slot is connected downward, the 1#-3# card slots are connected in series, and the same method is used for connecting the 4# and 5# card slots in series, thereby realizing flexible regulation of the output current value of the corresponding phase. If the 1#-5# slots are damaged or the resistor itself is damaged, the branch circuit can be quickly repaired by short-circuiting, changing positions, replacing resistors and changing the series structure while keeping the main power on.

[0058] The structural advantages of the utility model circuit are:

[0059] (1) The use of plug-in resistors makes capacity expansion easy and the expansion process does not require the main power to be cut off.

[0060] (2) MCCB switches and circuit breakers of various brands can be flexibly selected to meet various production power needs. The market space is large and procurement is easier.

[0061] (6) It is simple to use, safe and easy to operate, effectively reducing future operating and maintenance costs, change costs, etc., while also reducing the difficulty of construction during installation and having high reliability.

[0062] (5) The socket of the main bus 2 has a high protection level and is equipped with leakage protection to prevent accidental touch by personnel and tools, thus providing high safety.

[0063] (6) The total allowable current capacity is 250A-3200A, and the switch branch is 15A-1200A. It can be used with MCCB switches of various brands, and 1P, 2P, and 3P switches can all be used. Adding and reducing loads is quick and safe.

[0064] Embodiment 2

[0065] like Figure 6As shown, this embodiment discloses a distribution box, which includes a box body and a box door 100. The low-voltage distribution circuit for non-stop maintenance described in Example 1 is installed in the box body, and an instrument display screen 101 and an indicator light 102 are arranged on the outside of the box door 100, and the box door 100 is movably connected to the box body.

[0066] It should be noted that the instrument display screen 101 is provided with the DM2365S. The distribution box can be mounted on a wall or on a floor. The distribution box can be installed in a machine room or in a concealed return air channel, without occupying space in a production workshop.

[0067] Through the above technical scheme, due to the high degree of internal circuit integration of the electric box of the utility model, the design of the electric box itself requires a small volume, which can save space in the workshop. The distribution box has high adaptability for certain workshops with high electricity requirements, multiple load conditions, and complex production lines. For production lines where long power replacement time may cause large losses, the design of non-stop power plugging is very suitable, abandoning the traditional process of first cutting off the power, disassembling and then re-supplying the power, which can guarantee the production needs of the workshop production line, and it is easier to replace the corresponding size switches. At the same time, the distribution box has higher safety performance after optimization, providing safer protection for later operations, and has high economic benefits.

[0068] The above are all preferred embodiments of the present utility model, and are not intended to limit the protection scope of the present utility model. Therefore, any equivalent changes made based on the structure, shape, and principle of the present utility model should be included in the protection scope of the present utility model.

Claims

1. A low voltage power distribution circuit for non-stop maintenance, characterized in that: The invention comprises a main incoming line switch circuit breaker (1), a main bus (2), a plurality of branch switch circuit breakers (3) with different rated currents, a neutral bus (4) and a ground bus (5); the main incoming line switch circuit breaker (1) is electrically connected to a low-voltage power supply system, the main bus (2) is electrically connected to the main incoming line switch circuit breaker (1), a plurality of branch switch circuit breakers (3) are respectively electrically connected to the main bus (2), a neutral line access end of each branch switch circuit breaker (3) is connected to the neutral bus (4), a ground line access end of each branch switch circuit breaker (3) is connected to the ground bus (5), a bus end of the neutral bus (4) is connected to a neutral line of a low-voltage power supply system, and a bus end of the ground bus (5) is connected to a ground line of the low-voltage power supply system; The three-phase power supply access ends of the main busbar (2) are respectively connected to the three-phase power supply output ends corresponding to the main incoming line switch circuit breaker (1); the main busbar (2) is built with a phase line input bar (21) for connecting the corresponding three-phase power supply access ends and a phase line output bar (22) electrically isolated from the phase line input bar (21); a head end selection output unit (23), a plurality of middle selection output units (24) and a terminal selection output unit (25) are arranged between the phase line input bar (21) and the phase line output bar (22); the input end of the head end selection output unit (23) is connected to the phase line input bar (21); the first end selection output unit (24) and the second end selection output unit (25) are connected to the first end selection output unit (23); A selection output terminal is connected to the phase line output row (22); the first selection output terminal of the middle selection output unit (24) is connected to the phase line output row (22), and the input terminal of the middle selection output unit (24) is connected to the second selection output terminal of the head-end selection output unit (23) or the second selection output terminal of the middle selection output unit (24) of the previous stage; the input terminal of the terminal selection output unit (25) is connected to the second selection output terminal of the last stage middle selection output unit (24), and the output terminal of the terminal selection output unit (25) is connected to the phase line output row (22); the branch switch circuit breaker (3) is connected to the phase line output row (22).

2. The low-voltage power distribution circuit for non-stop maintenance according to claim 1 is characterized in that: The head-end selection output unit (23) comprises a single-contact main switch, a head-end slot with an input end and an output end electrically isolated, a head-end resistor and a head-end double-contact switch, one end of the single-contact main switch is connected to the phase line input row (21), and the other end is connected in series to the head-end slot and the head-end double-contact switch, a first selection output end of the head-end double-contact switch is connected to the phase line output row (22), a second selection output end of the head-end double-contact switch is connected to the input end of the middle selection output unit (24), and the head-end resistor is detachably electrically bridged to the head-end slot.

3. The low-voltage power distribution circuit for non-stop maintenance according to claim 2 is characterized in that: The middle selection output unit (24) comprises a middle slot with an input end and an output end electrically isolated, a middle double contact switch and a middle resistor, the input end of the middle slot being connected to the second selection output end of the head-end selection output unit (23) or the second selection output end of the middle selection output unit (24) of the previous stage, the output end of the middle slot being connected in series to the middle double contact switch, the first selection output end of the middle double contact switch being connected to the phase line output row (22), the second selection output end of the middle double contact switch being connected to the input end of the terminal selection output unit (25) or the input end of the middle selection output unit (24) of the next stage, and the middle resistor being detachably electrically bridged to the middle slot.

4. The low-voltage power distribution circuit for non-stop maintenance according to claim 3 is characterized in that: The terminal selection output unit (25) comprises a terminal slot with an input end and an output end electrically isolated, a terminal single-contact switch and a terminal resistor, wherein the input end of the terminal slot is connected to the second selection output end of the last-stage middle selection output unit (24), and the output end of the terminal slot is connected in series with the terminal single-contact switch and then connected to the phase line output row (22); the terminal resistor is detachably electrically bridged to the terminal slot.

5. The low-voltage power distribution circuit for non-stop maintenance according to claim 1, characterized in that: The three-phase power supply access terminals of the main incoming line switch circuit breaker (1) are respectively connected to the corresponding phase lines of the low-voltage power supply system, the neutral line access terminal of the main incoming line switch circuit breaker (1) is connected to the neutral line of the low-voltage power supply system, and the ground line access terminal of the main incoming line switch circuit breaker (1) is connected to the ground line of the low-voltage power supply system.

6. The low-voltage power distribution circuit for non-stop maintenance according to claim 1, characterized in that: The main incoming line switch circuit breaker (1) and the branch switch circuit breaker (3) are both MCCB circuit breakers.

7. The low-voltage power distribution circuit for non-stop maintenance according to claim 1, characterized in that: It also comprises an instrument indicating unit, which is electrically connected to the three-phase phase line output bus (22) in the main bus (2).

8. The low-voltage power distribution circuit for non-stop maintenance according to claim 1, characterized in that: The power supply input end of the branch switch circuit breaker (3) is provided with an insulating protection layer.

9. A distribution box, characterized in that: The invention comprises a box body and a door (100), wherein a low-voltage power distribution circuit for non-stop maintenance as claimed in any one of claims 1 to 8 is installed in the box body, an instrument display screen (101) and an indicator light (102) are arranged on the outside of the door (100), and the door (100) is movably connected to the box body.

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