How to Pick up the Best PV Junction Box

As the PV Junction Box is popular in the present industrial field, such as solar PV junction box and photovoltaic junction box, it is more and more important to choose a suitable PV junction box. The selection of PV junction boxes mainly depends on the information of the current size of the components. One is the maximum working current, and the other is the short-circuit current. It is obvious that the components can produce the maximum current at the time of the short-circuit current. The method of checking the rated current in accordance to the short circuit current is relatively much safer. On the contrary, it is less secure to choose the junction box based on the maximum operating current.

Therefore, for the most component manufacturers, there are actually no clear selection criteria, but the experience is more likely. The scientific selection should be based on the regular pattern of the current and voltage of the battery slice with the illumination intensity. So the operator must have a deep research of the region where the components are used. For example, the max value of the light intensity at that area and then figure out the max current by comparing the light intensity curve of current and light intensity. Afterwards, the rated current of the PV junction boxes can be decided.

Because the excessive heat will do harm to the diodes thermostat and reduce its service life, it is also a threat to the safety of the PV junction box itself. In addition, the long-time operation at high temperature is also harmful to the component safety, such as the loose at the back of rear panel. For the time being, the circulating PV junction boxes are able to work at the constant ambient temperature of 75 Celsius degree, 1 hour nominal rated current, and diode section temperature of above 179 Celsius degree. Some present PV junction box manufacturers made the design of relatively large terminal in order to reduce the temperature of the diode in the section of inner cartridge body. In the practice, however, the time of activating the capture-effect is not determined. As a result, the heat cannot be released after a time of work so that the accumulated heat will damage the PV junction boxes.

Another aspect of selecting the PV junction box is the overall resistance. Since this parameter involves the loss of power, the operator should connect the positive and negative terminals of the junction box together, and then measure the overall resistance value with a micro-ohm meter at the both sides of the terminal heads. This resistance value is the overall resistance of the junction boxes including wires during a long-term work. Besides, the greater the resistance values of the PV junction box the greater the power loss, which is very negative to the boxes. Most components of above 240W adopt double diode design, resulting in the larger volume of PV junction box.

There are several types of PV junction boxes. First of all, the traditional model has clamp connection, quick operation and easy maintenance. The disadvantages of the conventional one are also obvious. Due to the presence of the electrical terminals, the volume of the PV junction box is relatively large while the heat dissipation is also poor. Moreover, the cable hole on the case will lead to the decline of waterproof performance. Besides, the smaller conductive area results in less reliable connection for the PV junction boxes. The second type is the plastic sealed compact one whose advantage is the better waterproof and dustproof performance. Once the PV junction box is sealed, however, it is much more different to maintain. The third category is the one for special type of glass curtain wall. Such type of PV junction box has smaller volume so that there is less impact on the indoor light. Besides, the sealed design equips the photovoltaic junction box with good thermal conductivity, stability and waterproof and dustproof performance. Due to the solder connection, the weld of mental terminal is extremely inconvenient.