The Flooring Expert

The reason why the wire nose is larger than the diameter is mainly to reduce the contact resistance at the connection and strengthen the local heat dissipation capacity. For a wire, the overall resistance is evenly distributed, but no matter how much pressure you use to install the connection of the wire nose, the resistance at the contact part is always greater than that at the non connection of the wire, resulting in serious local heating, The solution is to inase the contact area and reduce the contact resistance as much as possible. At the same time, the larger wire nose will have higher heat dissipation capacity. The cable lug is generally about two specifications larger than the cable, because the cable is sometimes pressed into a fan shape, not a pure circle, and generally needs to be pressed by a hydraulic press before use. In the terminal block, touch force is one of the basic elements. If there is no satisfied touch pressure, the selection of good conductive materials is a drop in the bucket. If the touch force is too low, there will be displacement between the conductor and the conductive sheet, and then oxidation pollution will occur, which will inase the touch resistance and cause overheating. When the terminal crimping frame is selected, it has permanent connection without any environmental impact, large touch area and large touch force.

The conductor used for wiring terminals, connectors and bus bars is made of electrolytic copper (H65) as the basic material. The conductivity of copper is excellent, second only to silver. Since the wires connected to the terminals are made of copper, the same material and the same expansion coefficient will not cause the problem of loose connection.
1. Thermosetting plastic EP: it has good geometric stability, small water absorption and high leakage marking index. Flame retardancy is very high. When the temperature rises, it is stable and superior to thermoplastic, but the toughness is poor;
2. Glass fiber reinforced nylon pa-f: glass fiber reinforced nylon has strong rigidity and hardness, and its service temperature is higher than that of non reinforced nylon. Therefore, it is also applicable to the field of overvoltage protection. The water absorption of reinforced nylon is less than that of non reinforced nylon. In addition to the above differences, the other properties of the two materials are the same. According to UL94, the flame retardant grade of fiber reinforced nylon is Hb to V0, in which V0 material is dyed black in most cases;
3. Thermoplastic polycarbonate PC: such as high hardness, good impact toughness, transparency, dimensional stability, good insulation performance and good thermal stability. Transparent polycarbonate is particularly suitable as cover or identification material. Polycarbonate has stability against mineral acids, saturated fat carbohydrates, gasoline, lipids and oils. Polycarbonate is less resistant to solvents, benzene = lye, acetone and ammonia. Stress cracks may be formed when contacting with some chemical reagents;
4. Thermoplastic polyester PBT: PBT has good geometric stability. The material reinforced with glass fiber has high strength and heat resistance. At the same time, it also has reliable flame retardancy and excellent electrical properties;
5. Thermoplastic nylon 6.6: it has high requirements for the quality of the insulating shell of the combined terminal. Most of them are made of thermoplastic nylon 6.6. This kind of plastic can be processed economically through injection molding, is harmless to the environment and is conducive to recycling.

If the terminal products are stored under certain environmental conditions for a period of time, the material may change and the product performance will decline. If they are not used for a long time, the reliability of the products will not be guaranteed. The “shelf life” of the terminal refers to the storage time under certain environmental conditions from the completion of production and inspection to the installation. The effective storage period of the terminal refers to the period during which the quality and reliability of the terminal can meet the equipment requirements before installation. The basic effective period refers to the effective storage period without considering the quality level of the terminal.
The effective storage life of terminal blocks is related to the following three factors:
1. The quality of wiring terminals is the basic condition to ensure that the quality and reliability of wiring terminals will not degrade significantly during the effective storage period;
2. Environmental conditions for storage of wiring terminals;
3. Qualification criteria of wiring terminals after storage.
Gb4798.1 stipulates that the environmental level of the warehouse for storing precision instruments and wiring terminals is the highest, and the environmental conditions are: 20 ℃ ~ 25 ℃; RH is 20% ~ 70%; The air pressure is 70kpa ~ 106kpa. Qj2222a specifies general storage environment and special storage environment. The general storage environment standard specifies that the wiring terminal shall be stored in a clean, ventilated place without corrosive gas and controlled by temperature and relative humidity.