Abstract
The Large Helical Device is a fusion test device which has six pairs of superconducting coils that generate 4T of magnetic field at a plasma center. These coils are driven by six power supply units. Each unit has a two-paralleled double-star thyristor rectifier unit, a dc filter and a quench protection system. The quench protection system includes a new type of dc circuit breaker which consists of a conventional ac vacuum circuit breaker, a power fuse and a diode. Current control error of the power supply unit is limited by 0.04%+6A of target current value. Voltage ripple is also limited less than 1% (rms) of rated output voltage. Current range of these power supply units is 31.3kA to 17.3kA.
