System Engineering and Design of a Pulsed Homopolar Generator Power Supply for the Texas Experimental Tokamak
The design of a homopolar generator power supply for the Texas Experimental Tokamak (TEXT) is presented. Four series-connected disk type homopolar machines serve as inertial energy storage and conversion devices to supply 50-70 MW peak power to the toroidal field coil and ohmic heating coil circuits. The system is nominally operated at 150 MJ, 430 V to provide a 0.5 sec flat top, 160kA TF current pulse and a 0.3 sec, kA OH current pulse every 2.0 min on a continuous basis. The system has a maximum capacity of 200 MJ at a maximum open circuit voltage of 500 V. The homopolar machine design is described. The vertical shaft generators are excited by water-cooled, copper field coils and have ferromagnetic rotors. The magnetic reluctance torque tends to tilt the rotor between the cast steel pole pieces and hydrostatic journal bearings have been designed to maintain the angular position of the rotor. The rotor is suspended by a Kingsbury type hydrodynamic thrust bearing. The main ac powered oil supply system is backed by a completely redundant dc drive oil supply which is powered by station batteries. Control power is provided by a non-interruptible battery-inverter supply. The generators are driven by SCR controlled, variable speed de motor drives which are equipped with contactors and resistors for dynamic braking. Internal generators losses are removed by a combination of forced air ventilation and water cooling. The forced air system has provisions for the collection of brush wear debris. The overall generator configuration is designed to require minimum down time for brush maintenance. The TEXT homopolar generator system was designed under funding support provided by the O.S. Energy Research and Development Administration (ERDA) .