Dependency of the electrical resistance in crimped connections on mechanical stresses

Cables headed with crimped lugs are often used in test laboratories for rise temperature tests to validate electrical devices. Undesired power dissipation due to the electrical resistance of crimped connections can invalidate the outcome of these tests. The aim of the work made at the High Voltage and High Power Laboratory of the National Institute of Metrological Research (INRIM) has been the investigation of the dependence of the electrical resistance of crimped connections between lugs and a cable when the cable itself is submitted to mechanical stresses (twists and rotations). The resistance of crimped connections with lugs with different crimp profiles and of different manufacturers were analyzed. The crimp resistance was measured with a volt-ampere metric method. The obtained values, although less than 15 μΩtypical of a good crimp connection, remarkably changed in the first stresses, stabilizing after. The resistance of connections with lugs crimped with single indent changed less than that with lugs crimped with hexagonal profile, but more than that with lugs crimped with double indent. A comparison whit the behaviour of the resistance of a welded connection lug to cable submitted to similar stresses, was also made. This resistance was the most insensitive to mechanical stresses. Hence, the choice to weld the lugs is the most reliable but, on the other hand, the most expensive and time consuming for a test laboratory.