Do you know what are the common failures of power supplies box?

Do you know what are the common failures of power supplies box?

      (1) Failure caused by the influence of ambient temperature on low-voltage electrical appliances, The low-voltage electrical appliance in a power box consists of fuse, ac contactor，residual current action protector, capacitor and meter. The upper limit of ambient air temperature shall not exceed 40℃; The average temperature of surrounding air in 24h should not exceed 35℃; The lower limit of ambient air temperature shall not be lower than -5℃ or -25℃, The power box that farm net transforms runs outdoors, it not only gets the direct irradiation of sunshine to produce high temperature, at the same time in running oneself also can produce heat, so in midsummer high temperature season, the temperature inside box body will reach 60℃ above, at this time the temperature greatly exceeded the environment temperature that these electric appliance sets.
    (2) Fault caused by product quality. In the transformation of rural network, due to the large number of power boxes and the short construction period, the power box factory needed the supply of low-voltage electrical appliances in a hurry and a large number, which resulted in the phenomenon of not strict requirements on the quality of products, resulting in the failure of some products shortly after they were put into operation. For example, some types of AC contactor in the power box soon after the operation, because the closing coil of the contactor burned out, and can not run.
    (3) Failure caused by improper selection of electrical appliances in the power box Due to the improper selection of ac contactor capacity during manufacturing, the ac contactor with the same capacity is installed on different outlet circuits, and the unbalanced three-phase load is not considered, and the current level of some outlet contactor is not improved by one current level based on the normal selection model.