Hits:Updated:2019-02-18 13:02:29【Print】
Low-voltage switchgear is suitable for power transmission, power, petroleum, chemical, metallurgy, textile, high-rise buildings and other industries, as power transmission, distribution and power conversion. The product complies with the GB7251.1-2013 "Low-voltage switchgear" standard. Low-voltage switchgear is a product listed in the Catalogue of Compulsory Certification Products for 3C Certification.
Classification: from the structural approach
(1) fixed type
It can satisfy the position that each electrical component is reliably fixed in the cabinet. The shape of the cabinet is generally a cube, such as a screen type, a box type, etc., and a prismatic body such as a table top. This type of cabinet has a single row and is also arranged.
In order to ensure the shape and size of the cabinet, the stepwise combination of the components is often adopted. Generally, two pieces or two sides are formed first, and then the cabinets are formed, or the shape requirements are first met, and then the internal supports of the cabinet are sequentially connected. The lengths of the parts that make up the edges of the cabinet must be correct (the tolerances are negative) in order to ensure the geometric dimensions of all aspects, thus ensuring the overall shape requirements. For the two sides of the cabinet, due to the need for alignment, there should be no bulging in the middle.
In addition, from the perspective of installation, the bottom surface cannot be sunken. 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 lateral difference should be offset as much as possible, without causing the difference to accumulate, because the difference accumulation will cause the cabinet to deform. It affects busbar connection and component assembly eccentricity, stress concentration, and even affects the life of electrical appliances. Therefore, in the arrangement, the highest point of the foundation should be used as the installation reference point, and then the step should be gradually expanded. Under the condition that the dryness of the bottom surface is ideal and predictable, the method of expanding from the middle to the sides can also be adopted to make the accumulated difference cloth.
For easy adjustment, the tolerance accumulation is offset and the cabinet width tolerance is taken as a negative value. After the assembly of the various components of the cabinet is completed, it should be shaped as needed to meet the dimensional requirements of each part. For the manufacture of cabinets with large or large batch size, the fixtures should be fully considered to ensure the correct and uniform structure. The reference surface of the fixture is to be taken from the bottom surface. The positioning blocks in the fixture are arranged to facilitate the work. The outer door of the cabinet is affected by transportation and installation, and is generally adjusted during installation.
(2) Withdraw
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 is lightly moved when moving, and the positioning is reliable after moving in, and the drawers of the same type and specification can be reliably exchanged and extracted. The method of processing 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 part of the structure should have sufficient adjustment. As for the movable part, it must be replaced and the main components must be reliably loaded, so it must be higher. The mechanical strength and high precision, and the relevant part must have sufficient adjustment.
The process characteristics of manufacturing drawer type low voltage cabinet are:
(1) There must be a uniform reference for both fixed and movable parts;
(2) The relevant parts must be adjusted to the best position, and the special standard tooling should be applied when adjusting, including standard cabinet and standard drawer;
(3) The error of critical dimensions cannot be exceeded;
(4) Drawers of the same type and size should be interchangeable [1].
From the connection method
(1) Welded
Its advantages are convenient processing, strong and reliable; the disadvantages are large error, easy to deform, difficult to adjust, unsightly, and the workpiece can not be pre-plated. In addition, there are certain requirements for the welding clip:
1 good rigidity, not affected by workpiece deformation;
2 The outer dimension is slightly larger than the nominal size of the workpiece, which can offset the effect of post-weld shrinkage;
3 flat, simple and convenient operation, minimize the rotatable mechanism and avoid card damage;
4 In order to prevent welding and easy maintenance, it is necessary to select the workpiece support, and support the addition of anti-corrosion pad.
The post-weld deformation phenomenon of the workpiece is caused by the expansion of the heated molecules at the weld, the microscopic displacement caused by the extrusion, and the failure of the workpiece after cooling. In order to overcome the effects of deformation, the shaping process must be considered. The methods of shaping generally include:
1 Through the test to predict the deformation range of the workpiece, the workpiece is forced to deform in the opposite direction before welding, in order to reach the predetermined size after welding;
2 After welding, use a positive method to correct;
3 strikes, presses the relative shrinkage portion after welding, and obtains a stress balance;
4 After heating and welding, the relatively loose portion is the same as that of the welded joint;
5 The overall heat treatment of the components is carried out as necessary.
In addition, solder joint selection, weld orientation, welding sequence, and spot welding positioning have certain effects on post-weld deformation. If properly treated, the 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, parts can be standardized design, and pre-production inventory, frame size error is small. The disadvantage is that the welding is not as strong, the precision of the parts is required, and the processing cost is relatively increased. Fasteners are generally standard, and the types are mainly conventional screws, nuts and rivets, rivets, and pre-tightened and fine-tunable clamp nuts and pre-tensioned pull-up 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).
Process characteristics: shape by fixture, tooling positioning, and pressure washers as needed; riveting is generally required to be drilled, and pre-plated parts are to prevent the coating from being damaged; for components processed with precision machining centers or special equipment, such as connections When the aperture and the diameter of the fastener can maintain a small gap, the fixture can be assembled without a fixture, and the forming is performed once. The fastening of the guiding and positioning components should be first positioned with a special measuring tool and then tested by standard tooling.
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