Plasma current control device

This invention concerns an improvement for the plasma current control device in a tokamk type thermonuclear device. Plasma current is controlled by a selection section inputted with an output signal from a current control and restriction section and a signal corresponding to the terminal voltage for ohmic heating coils and selectively outputting one of the signals. That is, the current IOH from the ohmic heating coils is detected by a current detector and the sum of the current and a value corresponding to an allowable current In is amplified by the current control and restriction section and the resultant signal is used as an output signal X2. The magnitude between output signals X1 and X2 is compared in the plasma control section. Output voltage V2 for a thyristor conversion device is controlled based on an output signal X3 from the selection section selectively outputting the smaller signal. According to this invention, it is possible to control a plasma current of a tokamak type thermonuclear device including a lot of uncertain factors and having a difficulty for designing coils with large overload resistance. (K.M.)