Toroidal Field Reversing Switch

Abstract - A motor-driven, high-current switch is being designed by Stäubli Electrical Connectors in collaboration with Princeton Plasma Physics Laboratory to reverse the DIII-D Toroidal field coil current. The existing field reversing procedure requires approximately four hours of labor performed between run days to reconfigure the bus work, thus requiring a separate run day to complete experimental scans with both field directions. This typically results in different wall conditions which complicate the results or make them invalid. The proposed switch will complete the reversal process in approximately 4-5 minutes, between shots, so that wall conditions are not a factor, and easily fits within the 10-12 minute DIII-D shot cycle. The switch is a compact design fitting into a 157.5 x 41 cm envelope. The switch uses two copper pins that slide between Stäubli MULTILAM contacts. The switch is rated for total current of 180 kA DC for 10 seconds with a 12 minute repetition rate; the maximum operating coil current is 124 kA DC. The switch diagnostics include: voltage drop, current monitor, thermal monitors, position sensors, and motor torque. The switch is rated for 300 cycles per year, and 3000 cycles overall before contact replacement, with contact inspection yearly. The design details and operation of the switch are covered in this paper.