Development of highly stabilized & high precision power supply for KCCH cyclotron magnet

110 V/600 A, highly stabilized power supply have been installed at the Korea Cancer Center Hospital (KCCH) in Seoul, to energize water-cooled, resistive, high field research magnet for cyclotron. The power supply achieves a long term current stability of 20 ppm over one hour period with a short term ripple and noise variation of <20 ppm over a time period of one cycle. Power supply consists of a three-winding transformer, 12-pulse thyristor converter with interphase reactor, and a passive filter and a pass bank MOSFETs regulator. Various test results taken during the commissioning phase with a 70 kW resistive load and results taken with the research magnet for cyclotron are shown. This paper presents the detailed design of the power supply components. Problems with the power supply design and solutions are also presented. Some suggestions on how to improve the performance of these supplies are outlined.