A 250 MVA motor generator for large-scale plasma heating in the large helical device

Abstract For pulsed mode plasma experiments in the large helical device (LHD), high pulsive power has to be fed to the heating devices to produce currentless high-temperature and high-beta plasmas. The peak energizing power for these heating devices exceeds 200 MVA, and the energy consumed is 1000 MJ per 10 s pulse. To feed such enormous power, a motor generator (MG) system has been constructed and tested successfully. The MG is a vertical-shaft a.c. synchronous generator with nominal capacity 250 MVA. The maximum ejection energy is 1400 MJ per pulse at a repetition time of 5 min. The operational system is composed so as to deliver the power to various different loads, and the sequence is controlled voluntarily by operational computers near the load devices. The operational loss of the MG is reduced by using a computer network, so that an appropriate rotating speed and start time of acceleration of the MG are set automatically at every shot.