Failure analysis on bolt-type power connector's application

Bolt-type power connectors are widely used in China due to their simple structure and low cost. However, investigation shows that this kind of power connectors needs continuous maintenance and frequent replacement. By analyzing the failed connectors that were collected from different cities and sites, high connection resistance of most samples was found. Clearly high temperature has been occurred at each connector. Bolts of nearly 45% of the testing connectors appeared loosening, which caused low contact pressure, evidently the bolts were stress relaxed. Even the bolts were rusted and locked, the strand wires could still rock in the grooves of the connectors. Sliding and fretting tracks were clearly observed and appeared different kinds of morphologies. Serious contaminants and corrosive film covered on the groove surfaces, which caused high temperature rise and further enhanced stress relaxation. Surfaces of almost 58% samples preserved obvious melting or welding appearance, some of them were even burnt out, evidently there were gaps between wires and connector. Therefore, the structure of the bolt type power connectors can hardly stand for the harsh environment in China. It is also found that the material used for making connectors was not fitted to the standard.