Reasons for failure of distribution box electrical appliances
1.1 The fault caused by the influence of ambient temperature on low-voltage electrical appliances
The low-voltage electrical equipment in the distribution box is composed of a fuse, an AC contactor, a residual current action protector, a capacitor and a meter. These low-voltage electrical appliances are designed and manufactured in accordance with GB1497 "Basic Standards for Low-Voltage Electrical Appliances", and their normal working conditions are specified: the upper limit of ambient air temperature does not exceed 40 °C; the average value of ambient air temperature of 24 h does not exceed 35 °C The lower limit of the ambient air temperature is not lower than -5 ° C or -25 ° C.
The power distribution box transformed by the rural power grid is operated outdoors. It is not only exposed to direct sunlight, but also generates heat during operation. Therefore, during the hot summer season, the temperature inside the box will reach 60 °C or above. The temperature greatly exceeds the ambient temperature specified by these appliances, and failures due to overheating of electrical components in the distribution box may occur.
1.2 Failure caused by product quality
In the transformation of rural power grids, due to the large number of distribution boxes required and the short construction period, the distribution box factory needs the supply time of the low-voltage electrical appliances to be urgent and the quantity is large, thus the phenomenon that the quality of the products is not strict, resulting in Some products failed after they were put into operation. For example, some types of AC contactors cannot be operated because the contactor closing coil is burnt out shortly after the power distribution box is put into operation.
1.3 Failure caused by improper selection of electrical appliances in the distribution box
Since the AC contactor capacity selection is not very suitable during manufacturing, the same capacity AC contactor is installed for different outlet circuits, and the imbalance of the three-phase load is not taken into consideration, and the partial line contactor current level is not normal. On the basis of the selected model, a current level selection is increased, resulting in the occurrence of AC contactor burnout during summer high temperature season operation.
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