Toroidal field power supply for the TEXT tokamak

The power supply system for the toroidal field coil of the Texas Experimental Tokamak currently under construction is presented. The toroidal field coil produces a magnetic field of 3 T at the radius of the torus for 0.5 sec during the experiment, for which it requires a total energy of 76 MJ over a complete current pulse and a peak magnetic energy of 28 MJ. The power conversion system which provides this energy consists of a motor-generator-flywheel system, primary circuit breaker and two controlled rectifier modules. To overcome problems associated with power line waveform distortion, power source frequency changes, and line voltage relative phase-angle changes during trigger control shifts, firing pulse generation involves a modification to the phase lock principle to achieve line voltage harmonic rejection as well as close phase and frequency tracking. Power circuits through the firing generator are controlled by a voltage and current regulator loop, and the rectifiers are protected individually and as a system from overcurrent, overvoltage and commutation failure. Mechanical features include water cooling of the transformers and SCRs.