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SUMMARY: This paper presents the development results of a −1 MV dc filter and dc measurement systems for an ITER (International Thermonuclear Experimental Reactor) neutral beam injector (NBI) system. High accuracy of 0.5% and fast responsivity of 3.3 μs, −3 dB are required for the dc measurement systems: both dc voltage dividers and DCCTs. Circuit design and thermal flow design were carried out to clarify and minimize their effects on the accuracy and responsivity. The validity of the established design was demonstrated by the actual‐product tests; temperature rise of each components fell below the allowable value; inner components of dc filter withstood dc −1.2 MV; each voltage divider accurately measured the voltage during the dc −1.2 MV withstand voltage test; the voltage dividers and the DCCTs were adequate to the requirements of responsivity (3.3 μs, −3 dB). [ABSTRACT FROM AUTHOR]

SUMMARY: This paper presents development results of a five‐stage DC‐1MV Ultrahigh Voltage Generator for ITER. Each generator outputs −200 kV, and the total five generators are connected in series and outputs −1 MV. In order to realize the DC‐1MV output and 1‐h continuous operation, a feasibility of both gas insulation and gas cooling for semiconductor devices was validated. A simplified structure with stud‐type diodes and heatsinks resulted in the compatibility of enough insulation distance and wide cooling surface. Withstand voltage tests and a temperature rise test were performed for the actual equipment of the rectifier and the step‐up transformer. These test results verified the validity of the proposed design. [ABSTRACT FROM AUTHOR]