During the transformation of rural power grid, due to the large number of distribution boxes needed and the short construction period, the distribution box factory needed a large number of low-voltage electrical appliances, which resulted in the phenomenon that the requirements for product quality were not strict, resulting in the failure of some products shortly after they were put into operation.

During the transformation of rural power grid, due to the large number of distribution boxes needed and the short construction period, the distribution box factory needed a large number of low-voltage electrical appliances, which resulted in the phenomenon that the requirements for product quality were not strict, resulting in the failure of some products shortly after they were put into operation.

For example, some models of AC contactors cannot operate because the closing coil of contactors is burnt out soon after the distribution box is put into operation.

Faults caused by improper selection of electrical appliances in distribution box due to improper selection of AC contactor capacity during manufacturing, installation of AC contactors with the same capacity for different outgoing circuits, and failure to consider the imbalance of three-phase load, and failure to improve the current level selection of some outgoing contactors on the basis of normal selection of models, resulting in high temperature in summer The AC contactor is burnt out during seasonal operation.