Voltage enhancement of dc power supplies of superconducting coils of LHD

The Large Helical Device (LHD) is a helical-type fusion plasma experimental device using six superconducting coils to form a magnetic field. The fundamental operation of the LHD is performed under a dc magnetic field, and a power system which was suitable for steady state excitation was designed and constructed. With the progress in the fusion plasma research, dynamic experiments such as sweep of magnetic axis are planned, and require dynamic control of magnetic field. For this purpose, the output voltage of the original power supplies were not enough and the voltage enhancement of the dc power supplies were necessary. Therefore, the output voltages of power supplies were enhanced using additional pulse power supplies and the control system was modified for the pulse operation.