抄録
A direct digital control (DDC) system is adopted on feedback controllers of the poloidal field power supplies in the JT-60 tokamak. The system consisted of 5 CAMAC crates with each microcomputer and with some input/output modules, and their functions are instructing voltage (Ec) values calculated to phase controllers of thyristors. On upgrading of JT-60 (JT-60U), the DDC systems have been modified to fulfill the following requirements: (1) the processing time is under 0.5ms and hopefully 0.25ms to suppress intrinsic vertical instabilities of elongated plasmas; (2) in order to use resources of the power supplies effectively, new control methods which are (a) acting or stopping the circulating current and by-pass-pair operation as required and (b) changing over the current feedback control to the voltage control and vice versa have to be developed. A new system consists of a host computer which performs on-line processing such as setting the system under the discharge conditions, etc. and five microcomputers on VME-bus system. Functions of the microcomputers whose programs are written by C language are real-time processing such as calculating Ec values by new control algorithm and outputting Ec values on every 0.5ms and 0.25ms. The new VME system has been build and tested, and all requirements were accomplished. Moreover, It has controlled plasmas of JT-60U very well.
