Testing and Analysis of a Fast Discharge Homopolar Machine (FDX)

The Fast Discharge Experiment (FDX) is a 0.36 MJ, 200 V homopolar machine designed to discharge in one millisecond. This experiment is intended to establish the fundamental limitations involved in extracting energy in the shortest time from a flywheel using homopolar conversion. FDX features a room temperature 1.6 x 10 A-t copper coil pulsed by a 5 MJ slow discharge homopolar machine, two 30.5 cm diameter counterrotating aluminum rotors with flame sprayed copper slip rings, low inductance return conductors, coaxial transmission line, four fast closing (30 μsec) 1/2 MA making switches, hydrostatic journal bearings, squeeze film thrust bearings and dual brush activation systems. After initial testing of FDX was completed and data was analyzed, problems limiting performance were identified. Various components of the machine were redesigned and modified to correct these problems. A second set of tests, including short circuit discharges from various speeds, has recently been conducted. Results and analysis of these tests will be presented. New problems encountered as well as recommendations for additional work will also be given.