IMPROVEMENT OF A HIGH-CURRENT DC POWER-SUPPLY SYSTEM FOR TESTING THE LARGE SCALED SUPERCONDUCTING CABLES AND MAGNETS

A dc 75 kA power supply system was constructed to test the SC (superco nducting) R&D (research and development) cables and magnets for the La rge Helical Device (LHD). It consists of three 25 kA unit banks. A uni t bank has two double-star-rectifier connections with the inter-phase reactors. A digital feedback control method is applied to the automati c current regulation (ACR) in each unit bank. For shortening the dead time of the feedback process, a new algorithm of a digital phase contr oller for the ACR is investigated. A Bode diagram of the feedback proc ess is directly measured. It is confirmed that the dead time of the fe edback process is reduced to one sixth, and that the feedback gain of PID (proportional, integral and differential) compensation is improved by a factor of two from the original method.