three boxes

For the three boxes, there are different opinions, but they mainly refer to power distribution boxes and lighting distribution boxes (as well as dual power switching boxes), metering boxes (or metering boxes with both distribution functions), and control boxes (control boxes for power equipment such as water pumps and fans). The three boxes refer to: distribution box, metering box, and control box;

The three boxes in architecture refer to floor boxes (floor distribution boxes), meter boxes (i.e. unified meter boxes), and household boxes (i.e. indoor switch boxes for each household, classified according to the requirements of the power supply system and the location of use (primary distribution equipment, secondary distribution equipment, and final distribution equipment). Or it is called a main distribution box, distribution box, or switch box.

The three boxes have different installation methods, hanging on the wall and standing on the ground. They are 400~1000mm wide, 600~1800mm high, and 200~600mm deep. Inside, plastic or miniature circuit breakers, contactors, relays, and other electrical equipment are installed according to their purposes. They are connected by wires and equipped with inlet and outlet holes. Generally, there is no separation, and there is no fixed standard structure or configuration.

For a long time, the three box structure in China has been a welded structure, where steel plates are welded together as a whole after several bends. The welding workload is large, and the outer shell is painted after welding. The large volume of the outer shell makes it difficult to spray paint, and poor painting in blind spots and corners is greatly affected by environmental policies and regulations, such as welding and painting. The three boxes produced abroad are all spliced structures.

The use of splicing structure has always been a direction of effort for all parties. In the early days, low-voltage cabinets and medium voltage cabinets were also welded frame type. Nowadays, it is almost impossible to see low-voltage cabinets with welded frames. The assembly accuracy is good, there is no welding deformation, and aluminum zinc coated or galvanized sheet is used without surface treatment such as spraying. The advantages of beautiful appearance and easy non-standard design make the switchgear better and better.

Schneider's iPM distribution box, ABB's ARTU, etc. are all spliced distribution boxes. All prefabricated steel plates, components, standard parts, etc. are packaged in one box. After arriving at the factory, one worker can splice the boxes together with a tool. The modular and flexible components ensure that various solutions can be adapted to meet technical requirements, just like modular furniture, modular combination, small packaging, and convenient transportation.

There are generally three ways to assemble a distribution box. One is the fully bent form of steel plate, which is connected through slots and bolts. This design has fewer parts, thicker steel plate, heavier weight, and is sturdy. The amount of materials used is more than that of welding, and the precision requirements for parts are higher. The fitting of slots and other parts need to be accurate, with small adjustment margins, precise manufacturing, and precise assembly to ensure appearance and performance.

The second method is to install a backboard with vertical columns. Many foreign manufacturers adopt this method, where components are installed on the backboard. The backboard has high strength and plays a role in fixing the components and supporting the entire structure. During assembly, the backboard and columns are first assembled, followed by electrical components, wiring, etc. Finally, the side panel or door frame system is installed to complete the assembly of the entire distribution box.

The third form is sheet metal with five panels and some internal skeleton support plates. This method requires less steel plate usage and electrostatic powder coating on the exterior surface to ensure aesthetics. The internal skeleton can be made of aluminum zinc coated or galvanized sheet and installed directly. By connecting the skeleton to the panel, the adjustment margin is large, and even if there are small manufacturing errors in the panel, it can be adjusted. The skeleton board is fixed by crimping, and the distribution box is assembled using a tool. It is modular and functional, with different widths and heights, modular design, the same structure, light weight, no plug-in fit, and does not need to consider the influence of paint thickness.

After actual measurement, the weight of the reinforced box with internal reinforcement is 70% of that of the welded box, reducing production time by 60% and greatly improving efficiency. More importantly, it is low-carbon and environmentally friendly, with no welding parts. The shell sheet is integrated with stamping and prefabrication, and the internal reinforcement ribs are made of galvanized or aluminum coated zinc sheet. There is no welding, and small parts can be quickly painted with high painting quality and beautiful appearance. Easy to replace, easy to expand, can be expanded as a whole, and can also change the expansion size of a directional component with a screwdriver for replacement.