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Heretofore, joining large aluminum underground power cable to aluminum or copper power cable with compression connectors was not feasible because of premature failure of the connector joint under electrical current loading. Unlike the long andbulky compression connectors used on bare overhead power lines where space is not a premium, underground compression connectors must be short to keep manhole size small and to reduce the time required to insulate the joint with hand-wrapped tape or otherinsulating materials. Overhead line connectors receieve appreciable cooling from air currents whereas commonly used paper or plastic insulation restricts the cooling of underground cable joints. Metal particle-filled grease joint compounds used inoverhead line compression connectors are not used for underground cable for several reasons. First, its use is precluded because of the possiblity of migration of the compound into the paper or along the insulation resulting in voltage puncture of theinsulation from ionization. Secondly, joint compounds of grease do not offer much improvement over no compound because grease will move under pressure and therefore does not constrain relative movement of connector and conductor strands whereashardenable resins such as epoxy do.

If all goes according to plan, TUM's Professor Udo Lindemann (not to be confused with Udo Dirkschneider, the diminutive frontman of German heavy metal bands Accept and U.D.O.) predicts that "the high-voltage on-board systems of most electric vehicles to be based on aluminum by 2020."

Some of the issues the team is addressing are related to the way aluminum behaves over time. For example, as a TUM press release states, aluminum has a tendency to creep particularly at high pressure, meaning connectors would loosen over time. Even at lower temperatures, a paper by Austin Weber in Assembly Magazine explains that aluminum will flow when placed under constant pressure, so even if secured under twice the crimping pressure of copper, in time it will become loose as the metal flows from the pressure points.

Fabrizio Longo, Tyco Electronics product manager, says: "Many medium- and high-volume manufacturers of FHP motors for appliance, heating ventilation and air-conditioning (HVAC) equipment are evaluating a switch from copper to aluminium magnet wire to reduce raw material costs. Copper contributes on average about 30 per cent to the overall production cost of a FHP electric motor. Switching from copper to aluminium conductors can also reduce transportation costs, as aluminium is about one-third of the weight of copper. Our interconnection system allows manufacturers to easily and cost-effectively bridge the transitions many are making from copper to aluminium magnet wires."