Definition and types of low-voltage switchgear

Definition and types of low-voltage switchgear

Low voltage switchgear is suitable for industries such as power plants, petroleum, chemical, metallurgical, textile, high-rise buildings, etc., and is used for transmission, distribution, and energy conversion. The product complies with the standard provisions of IEC439-1 and GB7251.1-1997 "Low Voltage Complete Switchgear". The low-voltage switchgear has passed the national 3C certification. There are the following types:

GCL low-voltage withdrawable switchgear

GCS type low-voltage withdrawable switchgear

GCS type low-voltage switchgear

GCK withdrawable switchgear

GGD low-voltage fixed switchgear

Assembled low-voltage switchgear

MNSC type low-voltage withdrawable switchgear

MS low-voltage withdrawable switchgear

GCS type low-voltage withdrawable switchgear

MNSQH withdrawable low-voltage switchgear

GCS type low-voltage withdrawable switchgear

GCK (L) low-voltage switchgear

1. From the perspective of structural form

(1) Fixed:

It can ensure that all electrical components are reliably fixed in the designated position in the cabinet. The appearance of the cabinet is generally cubic, such as screen type, box type, etc., and there are also prismatic platforms such as desktop. This type of cabinet has a single row and also an arrangement.

In order to ensure the shape and size of the cabinet body, a step-by-step combination method is often adopted for each component, usually consisting of two pieces or left and right sides first, and then forming the cabinet body, or meeting the appearance requirements first, and then sequentially connecting the internal support parts of the cabinet body. The length of the parts that make up the edges of the cabinet body must be correct (with a negative tolerance) in order to ensure the geometric dimensions in all aspects and thus ensure the overall appearance requirements. For the two sides of the cabinet, the arrangement needs to be considered, and there should be no protrusions in the middle.

In addition, from the perspective of installation, there should be no sinking on the bottom surface. In the installation of the arrangement, the leveling of the foundation is a prerequisite, but there are certain errors in dryness and the cabinet itself. In the arrangement, it is necessary to try to offset the horizontal difference as much as possible, rather than causing the accumulation of difference, because the accumulation of difference will cause deformation of the cabinet, affect the busbar connection, cause component installation deviation, stress concentration, and even affect the lifespan of the electrical appliances. Therefore, when arranging, it is advisable to use the highest point of the foundation as the installation reference point, and then gradually cushion and expand the drainage. Under ideal and predictable conditions for the bottom surface dryness, the expansion method from the middle to both sides can also be adopted to evenly distribute the accumulated difference.

In order to facilitate adjustment and offset tolerance accumulation, the cabinet width tolerance is taken as a negative value. After the combination of various components of the cabinet is completed, shaping should be carried out as necessary to meet the dimensional requirements of each part. When manufacturing fixed or large batch cabinets, full consideration should be given to the use of fixtures to ensure the correct and unified structure. The reference plane of the fixtures should be based on the bottom surface, and the layout of each positioning block in the fixture should be based on the convenience of work removal. For the external doors of the cabinet, which are easily affected by transportation and installation, unified adjustments are generally made during installation.

2) Withdrawal type:

The withdrawable type is composed of a fixed cabinet body and a movable device part equipped with main electrical components such as switches. The movable part should be light and reliable when moved in, and drawers of the same type and specification can be reliably interchanged. The processing method of the cabinet body in the withdrawable type is basically similar to that in the fixed type. However, due to the requirements for interchangeability, the accuracy of the cabinet body must be improved, and the relevant parts of the structure must have sufficient adjustment. As for the movable device part, it must be able to be replaced while reliably supporting the main components. Therefore, it must have high mechanical strength and accuracy, and the relevant parts must also have sufficient adjustment.

The process characteristics of manufacturing drawer type low-voltage cabinets are: (1) there should be a unified reference standard for the fixed and movable parts; (2) The relevant parts must be adjusted to the optimal position, using specialized standard tooling, including standard cabinets and drawers; (3) The error of key dimensions cannot exceed the tolerance; (4) The interchangeability of drawers of the same type and specification should be reliable.

2. From the perspective of connection method

(1) Welding type:

Its advantages are convenient processing, sturdy and reliable; The disadvantages are large errors, easy deformation, difficulty in adjustment, and lack of aesthetics, and the workpiece generally cannot be pre plated. In addition, there are certain requirements for welding clamps:

① Good rigidity, not affected by workpiece deformation;

② The overall size is slightly larger than the nominal size of the workpiece, which can offset the impact of post welding shrinkage;

③ Flat, simple, and easy to operate, minimizing rotatable mechanisms to avoid jamming;

④ To prevent welding corrosion and facilitate maintenance and adjustment, it is necessary to choose a good workpiece support, and add anti welding corrosion pads for support.

The deformation phenomenon of workpieces after welding is caused by the stress caused by the expansion of heated molecules at the welding site, resulting in microscopic displacement and inability to reset after cooling. In order to overcome the influence of deformation, it is necessary to consider the shaping process. The methods of plastic surgery generally include:

① Predict the deformation range of the workpiece through experiments, force the workpiece to deform in the opposite direction before welding, in order to reach the predetermined size after welding;

② After welding, correct by using the correct method;

③ After striking and pressing welding, the relative shrinkage part is obtained to obtain a stress balance;

④ After heating and welding, the relatively loose and convex parts achieve the same shrinkage as the welding area;

⑤ If necessary, perform overall heat treatment on the components.

In addition, the selection of welding points, weld direction, welding sequence, and spot welding positioning all have a certain impact on the deformation phenomenon after welding. If handled properly, deformation can be reduced, but this depends on the specific situation.

(2) Fastener connection:

Its advantages are suitable for pre plating of workpieces, easy to change and adjust, easy to beautify, standardized design of components, and pre production inventory. The overall size error of the structure is small. The disadvantage is that it is not as sturdy as welding, requiring high precision of components and relatively high processing costs. Fasteners are generally standard components, mainly including conventional screws, nuts and rivets, pull rivets, pre tensioned and adjustable clamp nuts and pre tensioned pull nuts, as well as self tapping screws. There are also special fastening screws (such as most low-voltage cabinets imported from abroad use special fastening screws).

Process features: fixed with fixtures, positioned with fixtures, and equipped with pressure washers as needed; Riveting generally requires drilling, and pre plated parts should prevent damage to the coating; For components processed with precision machining centers or specialized equipment, if there is a slight gap between the connecting aperture and the diameter of the fastener, they can be assembled without fixtures and formed in one go; For the fastening of the guide and positioning components, special measuring tools should be used for positioning first, and then standard tooling should be used for testing

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