Grounding Requirements for Metal Box-Type Substation Housings 1. The box-type transformer is provided with a grounding conductor that can be connected to each component. The grounding conductor is provided with not less than two copper grounding terminals connected to the grounding grid, and the electrical contact area is not less than 160 mm2. The grounding conductor uses a copper conductor. When the rated short-circuit duration is 1 s, the current density does not exceed 200 A/mm2; when the rated short-circuit duration is 2 s, the current density does not exceed 140 A/mm2; when the rated short-circuit duration is 3 s The current density does not exceed 125A/mm2; when the rated short-circuit duration is 4s, the current density does not exceed 110A/mm2, and the minimum cross-section is not less than 30mm2.
2. Components connected to the grounding conductor include: box-type housing (metal part), switchgear frame or housing (metal part), cable grounding conductor and metal shield, metal frame of transformer, grounding conductor of control protection device Wait.
3. Install a sufficient number of grounding terminals on the grounding conductor. The grounding terminal is copper.
4. Box-type internal grounding connection: Set the grounding multi-strand soft wire between the frame, panel, door or other structural parts and the grounding system, and bolt connection to ensure the electrical continuity of the grounding system.
5. In line with the technical requirements of the drawings, the overall design should be as small as possible, light in weight, beautiful in appearance and reasonable in layout.
6. The cabinet should be able to withstand the following loads and impacts;
7. The top is subjected to a load of not less than 250ON/m2;
4. The external mechanical impact of the box is not less than 20J;
Environmental conditions for the use of metal box substation housings:
1. The maximum altitude is 2000m
2. Ambient air temperature: upper limit +45, lower limit -25oC
3. Relative humidity: the daily average is not more than 95%, and the monthly average is not more than 90%.
4. Wind speed: no more than 35m/S
5. No frequent and severe vibration, the earthquake intensity does not exceed 8 degrees 6. The installation tilt does not exceed
Clear Plastic Injection Molding parts usually made in PC, POM, PMMC, AS, PET, these clear plastic kits used widely in different application, such as auto light, medical devices, cosmetic packing, food container, water tank etc.
Comparing with other colored parts, strict requirements for appearance is a must for transparent Plastic Parts, which makes the injection molding processing more complex. Mold Design and injection molding condition are all determined factors to the final result, there are a few problems happen frequently in clear Plastic Molding process, we provide some solutions as below.
Silver streak: during the filling and cool-down process, the internal stress generated in the vertical direction and the orientation of resin flow occurs, while non-current orientation flow and orientation flow have different refractive index flash silk pattern, After its expansion, the clear plastic parts may be weak in strength.
Annealing is one of the options, for example, plastics in pc material can be heated to above 160 ℃ for 3 to 5 minutes, and then the natural cooling. As the silver streak is mainly because of the wet resin, so make sure the resin is dry before processing.
Air bubble: during injection molding process, the water and air in the resin are trapped inside the cavity or because of un-sufficient filling, excessive cooling cause a "vacuum bubble".
There are below methods to solve it:
- Dry up the clear plastic raw material before pouring them into the barrel, the water and air contained would be massively reduced.
- Slow down the filling process, leave it a little more time to allow the air escape.
Surface gloss defects: the possible reason is mold surface itself is not polished well, or the resin cooled down too fast so the resin are not actually in molded state, in this case, the injection molding temperature and ejection pressure need to be adjusted higher, cooling time need last longer.
Flow marks: the reason is because the melt viscosity is too large, the advanced melt flow has been condensed in the cavity, then coming melt flow after the condensation surface, leaving the surface with flow marks.
Solutions: optimize the melt flow, increase molding and mold temperature, ejection pressure, add vents, and use lubrication as less as possible.
Clear plastics production sometime could cause the producer a big loss because of the high appearance requirement, the re-grinded materials is not possible to be used again, any slight contamination of raw materials could cause whole batch of molded parts failure, mold making is required to be in a good condition.
Transparent Plastic Molding,Over Molding,Plastic Molding,Metal Injection Molding
PF Mold Co., Ltd. , http://www.pf-mold.com