Development and Construction of DC Power Supplies and a Coil Protection System

Abstract

The LHD has 12 superconducting coils that generate 3T of magnetic field at the plasma center, and their stored energy becomes 1GJ. These coils require large current DC power supplies that have a 17-30kA class output current, small control error less than 0.04% and high reliability for quench protection. This section introduces a DC power system to drive these coils. First, we give a description of the specifications and structures of power supplies, that are thyristor rectifiers, a LC passive filter and a current dump circuit. Next, the quench protection system which uses a novel DC circuit breaker, is described.