The common heat dissipation design is to install a heat sink. So, the junction box must have excellent heat dissipation. The reverse current will reduce the current generated by the board and affect the power of the board. The high temperature will accelerate the aging speed of the sealing ring and affect the sealing performance of the junction box There is a reverse current in the diode, and the reverse current will double when the temperature increases by 10 ℃. The components easily affected by high temperature in the junction box are sealing rings and diodes. In addition, the increase of ambient temperature will also increase the internal temperature of the junction box. At the same time, because of the contact resistance between the diode and the terminal, it will also generate heat. When the diode is on, it will generate heat. The diode and ambient temperature will increase the temperature in the junction box. Standard: GB 4208 2008 “enclosure protection level (IP code)” in the provisions of the dust-proof and waterproof grade IP grade, general junction box waterproof and dustproof grade IP65, IP67. V-0: the flame is extinguished within 30 seconds after two 10 second combustion tests. V-1: the flame is extinguished within 60 seconds after two 10 second combustion tests. V-2: the flame is extinguished within 60 seconds after two 10 second combustion tests. It is required that the burning rate of 3 to 13 mm thick samples should be less than 40 mm / min For samples, less than 3 mm thick, the burning rate is less than 70 mm / min Or go out in front of the 100 mm mark. The flame retardant grade increases gradually from Hb, V-2, V-1 to V-0: the lowest flame retardant grade in Hb: UL94 and CSA c22.2 no 0.17. Ultraviolet radiation has certain damage to plastic products, especially in the plateau where the air is thin and the ultraviolet irradiance is very high.įlame retardancy refers to the property that the material has or has been treated to delay the flame spread. Therefore, the junction box is required to have excellent high-temperature resistance and low-temperature resistance. The working environment of solar panels is very bad, some of them work in tropical areas, and the daily average temperature is very high Some working temperature is very low, such as high altitude area, high latitude area In some places, the temperature difference between day and night is very large, such as in desert areas. In addition, polyether also has the advantages of wear resistance, nontoxicity, and pollution resistance.Ģ.2 High temperature and humidity resistance It has the advantages of high rigidity, high heat resistance, fire resistance, high strength, and excellent electrical performance. At present, the most commonly used material is PPO (polyphenylene oxide), which is one of the five general engineering plastics in the world. They are all made of materials with strong weather resistance. The exposed parts of the junction box are the box body, box cover, and connector (PC). Weatherability refers to: when materials are used outdoors, they are subjected to the test of climate, such as the damage caused by light, cold and hot, wind and rain. The protection function of the junction box includes three parts: one is to prevent the hot spot effect through the bypass diode to protect the cell and solar panel Second, waterproof and fireproof are designed by sealing with special materials The third is to reduce the working temperature of the junction box and the temperature of the bypass diode through the special heat dissipation design, to reduce the loss of the leakage current to the solar panel power. To reduce the power loss of the junction box to the board as much as possible, the conductive material used in the junction box should have a small resistance, and the contact resistance with the outgoing line of the bus bar should be small. Inside the junction box, the current generated by the solar panel is led out and led into the electrical equipment through the terminals and connectors. The additional function is to protect the outgoing line from the hot spot effect.Īs a connector, the junction box serves as a bridge between solar panels and inverters. The photovoltaic junction box has two main functions: the basic function is to connect the photovoltaic panel and the load, to lead out the current generated by the photovoltaic panel, and generate power.
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