An explosion-proof junction box for rear wiring

Abstract

The present invention proposes an explosion-proof junction box with rear-row wiring, comprising a junction box base, insulating terminals, and terminal bolts. The length of the terminal bolts on the front-row terminals is set to a height that does not allow for user wiring installation, while the length of the terminal bolts on the rear-row terminals is set to a height that allows for user wiring installation. Insulating limit plates are added to the rear-row insulating terminals and terminal bolts, and insulating caps are added to the tops of the front-row terminal bolts. This invention overturns the traditional wiring method of explosion-proof junction boxes, solving the common problem of space constraints during user wiring and wiring in explosion-proof junction boxes both domestically and internationally. It improves the adaptability and versatility of explosion-proof junction boxes and complies with the provisions of GB3836.

Description

Technical Field

[0001] The invention relates to a junction box for electrical equipment, in particular to an explosion-proof junction box for rear wiring, which changes the wiring mode of a traditional explosion-proof motor. Background Art

[0002] For any three-phase asynchronous motor, it can only run at a fixed three-phase rated voltage. However, almost all three-phase asynchronous motors use a six-terminal output method. The reason for this is that the user can change the rated voltage of the motor by changing the "star-delta" connection method. Therefore, the rated voltage on the nameplate of the three-phase asynchronous motor is usually marked as: 220 / 380V (or 380 / 660V or 660 / 1140V ( The connection diagrams of "star connection" and "delta connection" are marked on the inner wall of the junction box cover, as shown in the figure. Figure 10 As shown, Figure 10 The wiring nameplate for the asynchronous motor is located on the inner wall of the motor's terminal box cover. To connect the wires, the user must first open the terminal box cover to see the wiring markings. The lines between the circles are "special copper connecting pieces." The user can easily change the rated voltage of the motor by adjusting the connection method of the connecting piece according to the schematic diagram. That is, the motor can either start and run at the rated voltage of 220V in delta connection or at the rated voltage of 380V in star connection. This is generally applicable to small-power motors. The incoming line to the terminal box is a three-phase four-wire (three power supplies and one ground) cable. Secondly, the starting current of the three-phase asynchronous motor is very large, generally 6 to 7 times its rated current. When the motor provides a six-terminal output structure, the user can use the "star-delta" conversion to start the motor in star connection and run it in delta connection to reduce the starting current of the asynchronous motor to 2 / 3 of the original value, so as to reduce the impact of the three-phase asynchronous motor on the power grid and electronic control system when starting. When converting "star-delta", the user needs to lead out the wires of the six terminals to the electrical control box respectively, and realize the conversion of "star start-delta operation" through electrical methods. At this time, the power supply input line of the junction box must be six (dual three-phase four-wire cable), which is generally suitable for high-power asynchronous motors.

[0003] Since the advent of explosion-proof asynchronous motors, almost 98% of explosion-proof junction boxes in the explosion-proof asynchronous motor industry are composed of the following structural elements:

[0004] 1. The six insulated output terminals are relative to the outlet of the junction box. The "phase sequence codes" of the front row output terminals are U1, V1, and W1, and the rear row output terminals are U2, V2, and W2. That is, when the user does not use the "type-angle" starting method, the three-phase power supply wiring is in the front row.

[0005] 2. The terminal boxes of explosion-proof motors M4, M5, M6, M8 and some M10 have one outlet. Therefore, for explosion-proof motors with a center height ranging from H63 to H225 (power 0.12KW-45KW) and some H250 and H280 (power 30KW-90KW), users can only use three-phase four-wire cables. That is, the starting and operation of the motor can only be carried out at a fixed rated voltage. This is because the rated current of small motors is relatively small, and the impact on the power grid and electronic control system during direct starting is within an acceptable range. The electrical control system is also relatively simple and low-cost, so users generally do not use the "star start-delta operation" conversion.

[0006] In addition, in the field of electrical connection, there are three commonly used methods for the introduction and connection of power cables: the bow-shaped sheet crimping method, the OT-type copper nose, and the DT-type copper nose connection method. The bow-shaped sheet crimping method takes up little space but has poor connection reliability, and is generally suitable for small-sized cables; the OT-type copper nose takes up appropriate space and has reliable connection, but the OT-type copper nose needs to be hot-melt-welded after crimping with the cable, so it is generally suitable for specific places; and for the introduction and connection method of high-current power cables, most users use the OT-type copper nose, but the tail of the OT copper nose is too long, and the front length space it occupies is almost 8 times that of the bow-shaped washer crimping method and 4 times that of the OT-type copper nose connection method, but its connection method is simple and highly reliable.

[0007] The design and manufacture of explosion-proof motors, including those in the explosion-proof electrical field, must comply with the national mandatory standard GB3836, which stipulates that the junction box must be an independent "explosion-proof cavity." Even more stringent are the minimum requirements for electrical clearance, creepage distance, mating surface length and clearance, casing strength, cable sealing, and anti-unplugging protection at the outlet. This results in very thick and bulky junction boxes for explosion-proof electrical equipment. Currently, all explosion-proof motor junction boxes, both domestically and internationally, offer users a "bow-shaped plate crimping" power wiring method. The reason for this is that the "bow-shaped plate crimping" method minimizes space and, while maintaining the same electrical clearance and creepage distance requirements as specified in GB3836, significantly reduces the size and overall size of the explosion-proof junction box. Despite this, for small explosion-proof motors, the junction box is almost as large as the motor itself, a phenomenon commonly known in the industry as a "big-headed baby." Another important reason is that if the explosion-proof motor junction box is designed and manufactured to be suitable for users to use copper noses, the DT copper noses are long and can rotate on the terminal bolts, which seriously affects the basic requirements of the electrical clearance. At present, there is no suitable solution at home and abroad, resulting in the fact that the explosion-proof motor junction boxes at home and abroad are still designed and manufactured as the "bow-shaped piece pressing method".

[0008] However, in the explosion-proof motor industry, it is a well-known fact that the "bow-shaped plate pressing method" as described above has poor wiring reliability. Especially for high-power motors, this power supply connection method is very prone to "loose crimping, small effective contact area, and localized heating", which eventually leads to failure. Therefore, in actual use, users have discarded the "bow-shaped plate" and used DT copper nose wiring. The consequence of this phenomenon has actually seriously violated the relevant provisions of GB3836 electrical clearance. However, due to the lack of a proper solution, manufacturers, users and even explosion-proof monitoring authorities have finally formed a situation where they are helpless and acquiesced - "the design is a bow-shaped plate pressing structure, but users actually use DT copper nose wiring", which poses a serious safety hazard.

[0009] Another well-known fact is that most users wire the power cable by looping it around the cavity of the junction box before wiring. This necessitates a reasonable turning radius after the power cable is crimped onto the DT copper lug, rather than running directly to the outlet. Therefore, the front-row wiring of the insulated terminals, the length of the DT copper lug plus the cable turning radius, requires a very large space in the front of the junction box. This is the fundamental reason why the petrochemical sector has been strongly complaining about the "small cavity of explosion-proof motor junction boxes." Some explosion-proof motor manufacturers even use two series of junction boxes: one with a small cavity, using bow-shaped pieces or OT copper lugs for wiring, suitable for use in relatively cramped equipment environments; and one with a large cavity, suitable for DT copper lug wiring and suitable for the open environment of the petrochemical sector. This has had a significant impact on the production management of explosion-proof motor manufacturers.

[0010] This situation is caused by the fact that domestic explosion-proof motor manufacturers currently prioritize motor performance, quality, and cost, but pay insufficient attention to explosion-proof junction boxes. Despite the long-standing concern within the petrochemical industry regarding the small cavity in explosion-proof motor junction boxes, no research has been conducted to understand the core issue. Summary of the Invention

[0011] In view of the defects of the existing explosion-proof junction box, the technical problem to be solved by the present invention is to provide an explosion-proof junction box that can connect wires from the back row and can only connect wires in the back row. It changes the traditional front-row wiring method to obtain a loose wiring space and enables users to comply with the provisions of GB3836 when using DT copper noses.

[0012] To solve the above technical problems, the technical solution adopted by the present invention is: an explosion-proof junction box with rear-row wiring, including a junction box seat, insulating terminals arranged on the junction box seat, wiring bolts installed on the insulating terminals, and connecting pieces assembled between the wiring bolts, wherein the length of the wiring bolts on the front-row wiring terminals is set to a height space without a user to install wiring, and the length of the wiring bolts on the rear-row wiring terminals is set to a height space with a user to install wiring.

[0013] The "phase sequence symbols" of the insulating terminals are adjusted to U1, V1, W1 in the rear row and U2, V2, W2 in the front row, and the "star-delta" connection markings on the inner wall of the junction box cover are changed accordingly.

[0014] Furthermore, in order to prevent the electrical clearance between the exposed portion of the copper nose and the top of the front row of wiring bolts from not complying with GB3836, an insulating cap is added to the top of the front row of wiring bolts.

[0015] An insulating limit partition is added to the rear insulating terminals and wiring bolts, and an upward-opening groove-shaped limit structure is provided on the insulating limit partition. The copper nose used for user wiring is placed in the groove on the insulating limit partition, and the limit structure can limit the rotation of the copper nose.

[0016] Furthermore, in order to prevent the electrical clearance between the exposed portion of the copper nose and the top of the front row of wiring bolts from not complying with GB3836, an insulating cap is added to the top of the front row of wiring bolts.

[0017] An extended insulating limit partition is additionally provided on the rear row insulating terminals and wiring bolts, and an upwardly open groove-shaped limiting structure is provided on the extended insulating limit partition. The copper nose for user wiring is placed in the groove on the insulating limit partition. The limiting structure can limit the rotation of the copper nose. The extended part of the extended insulating limit partition is long enough to cover the top of the front row wiring bolts.

[0018] The copper nose for user wiring is arranged on the rear insulating terminal and the wiring bolt, and an insulating limit partition is added on the rear insulating terminal and the copper nose. A downward-opening groove-shaped limit structure is provided on the insulating limit partition, and the copper nose is placed in the groove. The limit structure can limit the rotation of the copper nose.

[0019] Furthermore, in order to prevent the electrical clearance between the exposed portion of the copper nose and the top of the front row of wiring bolts from not complying with GB3836, an insulating cap is added to the top of the front row of wiring bolts.

[0020] The present invention creates a rear-row wiring explosion-proof motor junction box (or explosion-proof electrical explosion-proof junction box) designed using the above-mentioned technical solution. The box adopts "rear-row wiring when six insulated terminals" to fundamentally solve the current widespread problem of space constraints for user wiring and wiring at home and abroad. It improves the adaptability and versatility of the explosion-proof junction box, reduces the junction box cavity, reduces the junction box cost, and solves the aesthetic problems of the junction box and motor after matching. It completely overturns the long-standing traditional habits of the electrical industry. At the same time, it solves the long-standing dilemma of the explosion-proof motor industry, which has long been helpless and acquiesced to the fact that "the design is a bow-shaped sheet wire pressing structure, while users actually use DT copper nose wiring." It enables users to comply with the provisions of GB3836 even when using DT copper noses, which is of revolutionary significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram showing the structure of embodiment 1 of the present invention;

[0022] Figure 2 A schematic diagram showing the structure of embodiment 2 of the present invention;

[0023] Figure 3 A schematic diagram showing the structure of embodiment 3 of the present invention;

[0024] Figure 4 A schematic diagram showing the structure of embodiment 4 of the present invention;

[0025] Figure 5 A schematic diagram showing the structure of embodiment 5 of the present invention;

[0026] Figure 6 express Figure 5 A schematic diagram of a partially enlarged top view of the structure;

[0027] Figure 7 A schematic diagram showing the structure of embodiment 6 of the present invention;

[0028] Figure 8 A schematic diagram showing the structure of embodiment 7 of the present invention;

[0029] Figure 9 A diagram showing a comparison of the effects of the front row wiring and the rear row wiring of the present invention;

[0030] Figure 10 Indicates the wiring nameplate of the existing asynchronous motor;

[0031] Figure 11 Indicates the wiring nameplate of the asynchronous motor of the present invention. DETAILED DESCRIPTION

[0032] The following is a detailed description of an explosion-proof junction box for rear-row wiring according to the present invention with reference to the accompanying drawings.

[0033] The present invention is a rear wiring explosion-proof junction box embodiment 1, see Figure 1 The terminal block includes a junction box base 1, three front-row insulated terminals 8 and three rear-row insulated terminals 7 mounted on the base 1, front-row terminal bolts 5 mounted on the front-row insulated terminals 8, rear-row terminal bolts 2 mounted on the rear-row insulated terminals 7, and connecting lugs 6 mounted on the insulated terminals to connect the terminal bolts. The length of the front-row terminal bolts 5 is set to the height where there is no space for user wiring installation, while the length of the rear-row terminal bolts 2 is set to the height where there is space for user wiring installation. The rear-row terminal bolts 2 are equipped with copper lugs 3 or bow-shaped lugs for connecting cables. Connecting lugs 6 are also provided on the front-row terminal bolts 5. Depending on the connection method, the connecting lugs 6 on the front-row terminal bolts 5 can be connected to the corresponding rear-row terminal bolts 2 (delta connection) or to connect all three front-row terminal bolts (star connection). The phase sequence symbols for the insulated terminals are adjusted to U1, V1, and W1 for the rear row and U2, V2, and W2 for the front row. The "star-delta" connection marking on the inner wall of the junction box cover is also changed accordingly. Adjusting the terminal bolt length and phase sequence markings allows users to connect wiring in the rear row. This rear wiring method greatly reduces the requirements for the front space of the junction box as mentioned above, so that the junction box can be greatly reduced in size under the same conditions.

[0034] Example 2 of an explosion-proof junction box for rear wiring of the present invention, see Figure 2 In the structure of Example 1, when the user uses DT copper nose for wiring, the insulation treatment of the copper nose surface is very likely to be inadequate, resulting in an electrical gap between the exposed part of the copper nose 3 and the top of the front wiring bolt 5 ( Figure 1 4 in the figure) does not comply with GB3836. The present invention further provides an insulating cap 9 on top of the front row wiring bolt 5.

[0035] Example 3 of the explosion-proof junction box for rear wiring of the present invention, see Figure 3 In the structure of Example 1, an insulating limit partition 10 is additionally provided on the rear insulating terminal 7 and the wiring bolt 2, and an upwardly open groove-shaped limit structure is provided on the insulating limit partition 10. The copper nose 3 used for user wiring is placed in the groove on the insulating limit partition 10, and the limit structure can limit the rotation of the copper nose 3.

[0036] Example 4 of an explosion-proof junction box for rear wiring of the present invention, see Figure 4 In the structure of Example 3, in order to prevent the electrical gap between the exposed portion of the copper nose 3 and the top of the front row wiring bolt 5 from not complying with GB3836, an insulating cap 9 is further provided on the top of the front row wiring bolt 5.

[0037] Example 5 of an explosion-proof junction box for rear wiring of the present invention, see Figure 5and Figure 6 In the structure of Example 1, an extended insulating limit plate 11 is added to the rear-row insulated terminals 7 and the terminal bolts 2. An upwardly opening, groove-shaped limit structure 14 is provided on the extended insulating limit plate 11. The copper lugs 3 for user wiring are placed in the grooves of the extended insulating limit plate 11. The limit structure restricts the rotation of the copper lugs. The extended portion of the extended insulating limit plate 11 seals the ends of the front-row terminal bolts 5. In the figure, reference numeral 15 represents the raised portion of the extended insulating limit plate 11, and reference numeral 13 represents the phase sequence code for the insulated terminal wiring.

[0038] Example 6 of an explosion-proof junction box for rear wiring of the present invention, see Figure 7 In the structure of Example 1, the copper nose 3 for user wiring is arranged on the rear insulating terminal 7 and the rear wiring bolt 2, and an insulating limit partition 12 is added above the rear insulating terminal 7 and the copper nose 3. A downward-opening groove-shaped limit structure is provided on the insulating limit partition 12, and the copper nose 3 is placed in the groove. The limit structure can limit the rotation of the copper nose 3.

[0039] Example 7 of an explosion-proof junction box for rear wiring of the present invention, see Figure 8 In the structure of Example 6, further, in order to avoid the electrical gap between the exposed part of the copper nose 3 and the top of the front row wiring bolt 5 not complying with GB3836, the present invention also adds an insulating cap 9 on the top of the front row wiring bolt 5.

[0040] Figure 11 In the "star" line connection method, there is no connecting piece 6 in the front and rear rows of the terminal blocks. Therefore, there is an "electrical clearance" test in the front and rear rows of the terminal blocks.

[0041] The present invention overcomes the prejudice of electricians who are accustomed to wiring at the front row of terminals when wiring explosion-proof junction boxes. By realizing wiring at the rear row of terminals, the present invention solves the technical problem of people's desire for wiring space when using small explosion-proof junction boxes.

Claims

1. An explosion-proof junction box for rear wiring, comprising a junction box seat, an insulating terminal arranged on the junction box seat, a wiring bolt installed on the insulating terminal, and a connecting piece assembled between the wiring bolts, characterized in that The length of the wiring bolts on the front terminal row is set to the height space where there is no user installation wiring, and the length of the wiring bolts on the rear terminal row is set to the height space where there is user installation wiring; An insulating limit plate is added to the rear insulating terminals and wiring bolts. An upward-opening groove-shaped limit structure is provided on the insulating limit plate. The copper nose for user wiring is placed in the groove on the insulating limit plate. The limit structure can limit the rotation of the copper nose. Alternatively, an extended insulating limit partition is added to the rear insulating terminals and the wiring bolts, and an upwardly opening groove-shaped limit structure is provided on the extended insulating limit partition. The copper nose for user wiring is placed in the groove on the insulating limit partition. The limit structure can limit the rotation of the copper nose. The extended part of the extended insulating limit partition is long enough to cover the top of the front wiring bolts. Or the copper nose for user wiring is set on the rear insulating terminals and wiring bolts, and an insulating limit partition is added on the rear insulating terminals and the copper nose. A downward-opening groove-shaped limiting structure is set on the insulating limit partition, and the copper nose is placed in the groove. The limiting structure can limit the rotation of the copper nose.

2. The explosion-proof junction box for rear wiring according to claim 1, characterized in that The "phase sequence symbols" of the insulated terminals are adjusted to U1, V1, W1 in the rear row and U2, V2, W2 in the front row, and the "star-delta" connection on the inner wall of the junction box cover is changed accordingly.

3. The explosion-proof junction box for rear wiring according to claim 1, characterized in that Insulating caps are also added to the tops of the front row of wiring bolts.

4. The explosion-proof junction box for rear wiring according to claim 1, characterized in that Insulating caps are also added to the tops of the front row of wiring bolts.

5. The explosion-proof junction box for rear wiring according to claim 1, characterized in that Its characteristics are Insulating caps are also added to the tops of the front row of wiring bolts.

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