Development and testing of experimental materials and designs for high-current, high slip speed generator contacts

The development of homopolar generators (HPGs) capable of producing high currents at high slip speeds requires current collectors that exhibit good electrical properties as well as good frictional properties at high temperatures. The authors have focused on developing and testing materials and designs that will respond to these requirements at a reduced wear rate. Methods for actively cooling the contact/slip surface interface were investigated and are discussed. Parameters of concern include wear, current density, slip speed, and voltage drop at the interface. Data compiled from experiments run on a 5-MJ HPG capable of a maximum slip speed of 160 m/s are presented. It is concluded that introduction of actively cooled contacts into a homopolar generator does present problems in both implementation and fluid management, but the potential result is a sliding contact capable of pulsed operation at high slip speeds and current densities than existing contact designs presently afford, or continuous operation at lower performance levels