DESIGN AND OPERATION OF A 40-MW, HIGHLY STABILIZED POWER-SUPPLY

Four 10-MW highly stabilized power supply modules have been installed at the National High Magnetic Field Laboratory in Tallahassee, FL, to energize water-cooled resistive high-field research magnets. The power supply modules achieve a long-term current stability of 10 ppm over a 12-h period with a short-term ripple and noise variation of <10 ppm o ver a time period of one cycle. The power supply modules can operate i ndependently, feeding four separate magnets, or two, three, or four mo dules can operate in parallel. Each power supply module consists of a 12.5-kV vacuum circuit breaker, two three-winding step-down transforme rs, a 24-pulse rectifier with interphase reactors, and a passive and a n active filter. Two different transformer tap settings allow rated de supply output voltages of 400 and 500 V. The rated current of a suppl y module is 17 kA and each supply module has a one-hour overload capab ility of 20 kA. The isolated output terminals of each power supply mod ule are connected to a reversing switch. An extensive high current bus system allows the modules to be connected to 16 magnet cells. This pa per presents the detailed design of the power supply components. Vario us test results taken during the commissioning phase with a 10-MW resi stive load and results taken with the research magnets are shown. The effects of the modules on the electrical supply system and the operati onal behavior of the power factor correction/harmonic filters are desc ribed. Also included are results of a power supply module feeding a su perconducting magnet during quench propagation tests. Problems with th e power supply design and solutions are presented. Some suggestions on how to improve the performance of these supplies are outlined.