Development of a 5.8 MW dual output high voltage power supply with pulse step modulator module for KSTAR Helicon current drive system

Abstract In this study, a 5.8 MW high voltage power supply was developed for two 1.2 MW klystrons to operate the upgraded KSTAR helicon current drive system. The developed power supply was configured to connect 180 pulse step modulator (PSM) modules using semiconductor switches connected in series to produce an output with a rating of −92 kV and 64 A for 300 s. To operate the klystron individually, the output of the cathode power supply (CPS) is divided into two high voltage switches (HVSs). The HVS not only operates as an individual switching, but also cuts off the energy from being transferred to the load within 5 μs in case of an arc or short circuit. At this time, the energy should be 5 J or less. The individual PSM of the power supply is controlled by optic shifting distributor controller, and the overall control and protection are controlled by the CPS controller. Currently, this power supply is installed at KSTAR, and has been tested up to the maximum voltage of −92 kV for performance verification. In addition, the arc energy blocking performance was verified through the wire burning test of HVS. Furthermore, an actual load test was conducted on one klystron installed for operation; an RF test was conducted up to −70 kV, and the maximum output was measured up to 620 kW