Copper-to-aluminum transitions in high direct-current bus systems

A number of recent papers have discussed issues related to electrical applications of various types of copper-to-aluminum welds. Little field experience, however, has been discussed. This paper describes techniques used at a large electrochemical manufacturing site for making copper-to-aluminum transitions in high direct-current bus systems. After a brief historical treatment of problems with bolted copper-to-aluminum transitions, various explosion-bonded and roll-bonded bus transition designs and experiences are discussed. Two roll-bonded copper-to-aluminum transition designs are described, with mixed performance records. Some specific explosion-bonded transition designs are described, along with an explosion-bonded copper-to-aluminum transition with a titanium interlayer to permit the use of higher fabrication temperatures without detriment to the strength of the metal-to-metal bond. Explosion-bonded transitions are shown to have good performance records