Classification of Low Voltage Switchgear

Low-voltage switchgear is suitable for industries such as power plants, petroleum, chemical, metallurgy, textiles, high-rise buildings, etc., for power transmission, distribution and power conversion. In order to meet the needs of different venues and different customers, low pressure switch cabinets are divided into different classifications in order to adapt to the environment. The classifications are different, and the functions and effects of the products are different.

Ⅰ、Low-voltage switchgear is classified according to its structure:

1. Fixed:

It can satisfy that the electrical components are reliably fixed in the determined position in the cabinet. The shape of the cabinet is generally cubic, such as screen type, box type, etc., and there are also prisms such as table top. This kind of cabinet has a single row, but also has an arrangement.

In order to ensure the shape and size of the cabinet, the components are often combined step by step. Generally, two pieces or left and right sides are formed first, and then the cabinet is formed, or the shape requirements are met first, and then the internal supports of the cabinet are connected in sequence. The length of the parts composing the edges of the cabinet must be correct (the tolerance is negative) to ensure the geometric dimensions of all aspects, thereby ensuring the overall shape requirements. For both sides of the cabinet, due to the need for arrangement, there should be no bulge in the middle.

In addition, from the perspective of installation, there should be no sag on the bottom surface. In the arrangement and installation, the foundation leveling is a prerequisite, but the dryness and the cabinet itself have certain errors. In the arrangement, the horizontal difference should be offset as much as possible, and the difference should not be accumulated, because the accumulation of the difference will cause the cabinet body to deform. , It affects the bus connection and causes the components to be installed out of place, stress concentration, and even affects the life of electrical appliances. Therefore, it is advisable to use the highest point of the foundation as the installation reference point when arranging, and then gradually expand the arrangement. Under the condition that the bottom dryness is ideal and predictable, the arrangement can also be expanded from the middle to the two sides to make the accumulated difference evenly cloth.

In order to facilitate adjustment and offset the accumulation of tolerances, the cabinet width tolerances are all negative. After the combination of each component of the cabinet body is completed, if necessary, it should be reshaped to meet the shape and size requirements of each part. Full consideration should be given to the use of tooling fixtures when manufacturing cabinets with a finalized shape or large batches to ensure the correct and uniform structure. The reference surface of the fixture should be taken from the bottom surface. The layout of the positioning blocks in the fixture should be based on the ease of work removal. Because the outer doors of the cabinet are easily affected by transportation and installation, they are generally adjusted uniformly during installation.

2. Withdrawal type:

The draw-out type is composed of a fixed cabinet and a movable device part equipped with main electrical components such as switches. The movable part should be light and portable when being replaced, and the positioning should be reliable after being moved in, and the drawers of the same type and specification can be reliably interchanged and drawn out The processing method of the cabinet part in the formula is basically similar to that of the fixed cabinet. However, due to the interchange requirements, the accuracy of the cabinet must be improved, and the relevant parts of the structure must have sufficient adjustments. As for the movable device part, it must be able to be replaced, and the main components must be reliably installed, so it must be higher. With high mechanical strength and high precision, the relevant parts must have sufficient adjustment.

The technological characteristics of manufacturing drawer-type low-voltage cabinets are:

1). The fixed and movable parts must have a unified reference standard;

2). The relevant parts must be adjusted to the best position, and special standard tooling shall be used when adjusting, including standard cabinets and standard drawers;

3). The error of the critical dimension can not exceed the tolerance;

4). The interchangeability of drawers of the same type and specification must be reliable.  

Ⅱ、Low-voltage switchgear is classified from the connection mode:

1. Welding type:

Its advantages are convenient processing, sturdiness and reliability; disadvantages are large errors, easy deformation, difficult adjustment, and poor aesthetics, and the workpieces generally cannot be pre-plated. In addition, there are certain requirements for welding clamps:

1). Good rigidity, will not be affected by the deformation of the workpiece;

2). The outline size is slightly larger than the nominal size of the workpiece, which can offset the effect of shrinkage after welding;

3). Flat, simple and convenient operation, minimize the rotatable mechanism to avoid jamming;

4). In order to prevent welding corrosion and easy maintenance and adjustment, it is necessary to select the workpiece support, and the support should be equipped with anti-welding pads.

The post-welding deformation of the workpiece is caused by the stress caused by the expansion of heated molecules at the welding place during welding, the microscopic displacement caused by extrusion, and the inability to reset after cooling. In order to overcome the influence of deformation, the shaping process must be considered. Shaping methods generally include:

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

2). Correction using positive method after welding;

3). The relative contraction part after punching and pressure welding, and the stress balance is obtained;

4). After heating and welding, the relatively loose convex part can achieve the same shrinkage as the welding part;

5). If necessary, heat the components as a whole.

In addition, welding point selection, welding seam direction, welding sequence, and spot welding positioning have a certain influence on post-welding deformation. If handled properly, deformation can be reduced, but this depends on the specific situation.

2. Fastener connection:

Its advantages are that it is suitable for workpiece pre-plating, easy to change and adjust, easy to beautify, parts can be standardized design, and can be pre-production stocked, and the frame size error is small. The disadvantage is that it is not as strong as welding, requires high precision of parts and components, and the processing cost is relatively increased. Fasteners are generally standard parts, and their types mainly include conventional screws, nuts and rivets, pull rivets, as well as pre-tightened and finely adjustable clamp nuts and pre-tightened tension nuts, as well as self-tapping screws. There are also special fastening screws (for example, most of the low-voltage cabinets imported from abroad use special fastening screws).

Technological characteristics: Fix the shape with fixtures, position by tooling, and equip with pressure washers if necessary; riveting is generally equipped with drills, and the pre-plated parts should prevent the coating from being damaged; for components processed with precision machining centers or special equipment, such as each connection When the aperture and the diameter of the fastener can maintain a slight gap, it can be assembled without clamps and formed at one time; for the fastening of the guide and positioning parts, the special measuring tool should be used to first locate and then use the standard tooling to test.