Medium power pulsed power supply experience

The H-1Heliac National Facility at the ANU is a 1.0 tesla magnetically confined plasma with pulsed power and diagnostics. High temperature plasma operation requires pulsed power an order of magnitude smaller than the largest installations. Experience gained at the ANU is therefore directly relevant to large industrial power supplies. Fusion research requires very low ripple magnetic field currents. Large pulsed loads create problems on supply networks; H-1 imposes a peak power demand of nearly 14 MW on Canberra´s 11 kV CBD supply. A high pulse number output rectiformer is required for low ripple with a large SVC to control voltage fluctuations. A DC-DC converter based on proven traction GTO chopper technology was adopted to solve these design constraints. Interleaving the choppers gives a 2.0 kHz switching frequency at 14 kA. Innovative hardware and control systems including a state machine sequencer for the many auxiliary supplies and services required to be present with the main pulsed field have dramatically reduced technical support man-hours. Very ambitious targets for field current ripple resulted in ripple as low as 1 part in 4000. The paper discusses power supply and ancillary controls design, diagnostic equipment, and highlights effective and ineffective aspects of control technology. Performance records of ripple, ripple spectra, stability and slew rate are presented.