What is a solar photovoltaic module junction box?
The solar photovoltaic module junction box mainly protects the entire power generation system (if the module is short-circuited, the junction box automatically disconnects the short-circuit battery string to prevent the entire system from burning out) and functions as a current transfer station.
Note that the diode in the junction box is selected according to the type of cell in the assembly.
①The function and lead method of the junction box of solar photovoltaic module
The special junction box for solar cell module is a component that connects the internal output circuit of the battery module with the external circuit. The junction box mainly protects the entire power generation system and acts as a current transfer station. When the components in the array are blocked by dark clouds, tree branches, bird droppings, etc., the bypass diode in the junction box will bypass the current that would otherwise pass through the battery components blocked by the blocking object, otherwise a hot spot effect will occur. If the component is short-circuited, the junction box automatically disconnects the short-circuited battery string to prevent burning of the entire system. The junction box transmits the electricity generated by the solar cell to the external circuit (to the charging control system), which acts as a current transfer station. In addition, the junction box is also the “tie” of the entire solar array, connecting many components in series to form a power generation unit.
Lead method of the solar cell module junction box: The positive and negative bus bars (wider interconnection bars) drawn from the battery panel enter the junction box, and are connected to the corresponding position in the junction box by plugging or soldering. The outer leads are also connected to the junction box by methods such as plugging, welding and screw crimping.
Some junction boxes are also directly equipped with output cable leads and cable connector plugs to facilitate quick connection of battery components or square arrays. When the lead length is not enough, you can use an extension cable with a connector plug to connect.
There are many varieties of solar photovoltaic module junction boxes and different styles. According to the connection method with the bus bar, they can be divided into the snap-on type and the welding type. Except for the connection method with the bus bar, the structure of the two is basically the same.
The conventional junction box is basically composed of the following parts: base, conductive block, diode, card interface/welding point, sealing ring, box cover, back cover and accessories, connector, cable, etc.
②The performance of the solar photovoltaic module junction box
The required performance of a junction box for a qualified solar cell module: the internal cavity volume can effectively reduce the internal temperature, the heat dissipation performance is good, the connection is safe, and the bypass diode should be installed in the junction box or the bypass should be installed. Diode; The shell is waterproof, dustproof, anti-aging, and UV resistant; the connection is good and error-free, and can meet the requirements of electrical safety performance; the body resistance should be small in order to reduce the power loss of the junction box as much as possible.
③Selection of junction box of solar photovoltaic module
When choosing a solar photovoltaic junction box, you must be clear: the size of the module’s working current is the key to choosing a junction box. When choosing, generally make the rated working current of the solar photovoltaic junction box be 1.25~1.4 times of the maximum working current of the solar module. This is an empirical data. After this data is confirmed, it is best to see whether it is greater than the short-circuit current of the component. It is stricter and safer to calculate the rated working current of the junction box according to the short-circuit current.
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