2022-01-12
Solar panel connection boxes are used by electricians to protect cables from physical shocks and insect bites by using cable ducts outside the cables. And at the connection of the cable (or at the corner of the cable pipe), use the junction box as a transition. Two cable tubes are connected to the junction box, and the cables inside the tubes are connected inside the junction box. Solar connection box plays the role of protecting and connecting the cables.
The function of the Solar junction box is to connect the electricity generated by the PV module to the external wiring. Since solar panels often need to be used in harsh outdoor environments and have a warranty of up to 25 years, solar panels also have high requirements for connection boxes. In addition to ensure the reliability of the connection, to ensure the safety of the internal wiring, solar panel connection box also needs to have a high anti-aging, anti-UV capability; to have a high level of waterproof and dustproof, generally to achieve IP67 or more; can withstand high current (generally require more than 20A), high voltage (generally 1000 volts, many products can reach 1500 volts); use a wide range of temperature (-40 ℃ ~ 85 ℃), low working temperature and a series of requirements. Also, to attenuate and avoid the hot spot effect, diodes are integrated inside the solar junction box.
Composition of pv panel junction box: box cover (including sealing ring), box body, terminals, diodes, cables, and connectors.
The base material of the box body and cover of the solar panel connection box is commonly used PPO, which has the advantages of good rigidity, high heat resistance, non-combustibility, high strength and excellent electrical properties. In addition, PPO also has the advantages of wear resistance, non-toxic, pollution resistance, good weather resistance, etc. PPO has one of the smallest dielectric constants and dielectric losses among engineering plastics, and is virtually unaffected by temperature and humidity, allowing it to be used in low, medium and high frequency electric fields. The unmodified pure PPO has high melt viscosity, poor processability and moldability, and cannot be molded by injection molding machine. In order to solve this problem, PPO can be modified by physical or chemical methods, and the modified PPO is called MPPO. Hot melt type MPPO is molded by injection molding machine to form the box body. The manufacturing method of the lid is the same as the box body, only the mold is different. To improve the waterproof performance, the lid will have a seal made of silicone.
The input side of the terminal is connected to the sink bar of the solar panel, and the output side is connected to the cable. The material of the terminal is generally pure copper or tinned copper, tin-plated copper is copper with a thin metallic tin coating on the surface. Tin mainly plays a role in protecting copper to prevent copper from being oxidized to form copper green to affect the conductivity. At the same time, the low melting point of tin, easy to weld, and good electrical conductivity, you can also use chromium-plated copper to do the terminal.
Diodes have the characteristics of a single conductor. Diodes can be classified as rectifier diodes, fast diodes, voltage regulator diodes and light emitting diodes.
Commonly used cables have copper or tinned copper conductors inside and two protective layers outside, namely polyvinyl chloride (PVC) insulation plus PVC jacket, but PVC does not meet aging requirements and contains halogen, which releases chlorine gas when heated and is not very safe. Photovoltaic cables need irradiated cross-linked polyolefins in addition to conductors (irradiation cross-linking technology refers to the cross-linking reaction of macromolecules achieved through irradiation, so that the linear polymer becomes a polymer with a three-degree space network structure, so that its long-term allowable operating temperature is increased from 70°C to more than 90°C, and the short-circuit allowable temperature is increased from 140°C to more than 250°C, while maintaining its original excellent electrical properties and improving the actual use of performance. ) Inside the photovoltaic cable is a copper wire with a cross-sectional area of 4mm2. If the nominal current of the solar panel (less than 10 amps) is calculated, a 2.5mm2 copper wire is sufficient, but considering that solar panels often work under high temperature conditions, when the cable capacity is reduced and the system current is relatively high, a larger cross-sectional area of copper wire should be used to ensure system safety.
Connectors block or isolate between circuits, bridging the flow of current so that the circuit achieves its intended function. A pair of connectors consists of a male connector and a female connector, using PPO as the insulating material. The male connector is used for the positive terminal of the component and the female connector is used for the negative terminal.
Many solar connection boxes use silicone potting adhesives to protect their internal components and improve thermal performance. Junction box potting adhesive is mainly based on two-component silicone. Two-component silicone is composed of A, B two kinds of glue, A type of glue is called base glue, B type of glue is called curing agent. When the AB type glue is mixed in a certain proportion before use, it is put into the junction box for curing after mixing. The mixing process should be extra careful to minimize the mixing of air. Silicone potting adhesive can be cured at room temperature (25℃) or by heating. Room temperature curing potting adhesives can also be accelerated by heating. The curing agent should be premixed before use, as some precipitation may occur during delivery and storage. The curing agent tends to react with moisture in the air, so extra care should be taken to avoid contact with air before use.
1. MPPT function: configure the maximum power tracking technology and control device for each panel through software and hardware, this technology can maximize the possibility of improving the power generation efficiency reduction of the power station caused by the characteristics of different panel arrays, and reduce the “barrel effect” on the power plant efficiency, can greatly increase the power generation capacity of the power station. From the test results, the maximum power generation efficiency of the system can even be increased by 47.5%, increasing the return on investment and greatly reducing the payback period.
2. Intelligent shutdown function under abnormal conditions such as fire: In the event of a fire, the solar connection box’s built-in software algorithm will cooperate with the hardware circuit to determine within 10 milliseconds whether an abnormality has occurred, and take the initiative to cut off the connection between each panel, the voltage of 1000V down to about 40V human acceptable voltage to ensure the safety of firefighters.
3. The use of MOSFET thyristor integrated control technology, instead of the traditional Schottky diode. When shading occurs, you can instantly start the MOSFET bypass current to protect the safety of the panel, while the MOSFET because of its unique low VF characteristics, so that the overall heat generation in the junction box is only one tenth of the ordinary junction box, the technology greatly extends the service life of the junction box, to better protect the life of the battery.
Dongguan Slocable Photovoltaic Technology Co.,LTD.
Add：Guangda Manufacturing Hongmei Science and Technology Park, No. 9-2, Hongmei Section, Wangsha Road, Hongmei Town, Dongguan, Guangdong, China
TEL：0769-22010201
