Design and commissioning of a TF coil power system using deep-cycle batteries for versatile experiment spherical torus (VEST)

A toroidal field (TF) coil power system has been designed and successfully commissioned to be suitable for the research objectives of VEST (Versatile Experiment Spherical Torus) which was recently constructed at Seoul National University. The TF coil power system for VEST is fabricated using a series-parallel connection of 200 deep-cycle batteries with 100 A h capacity so as to generate flat-top TF field of 0.12 T on magnetic axis for sufficiently long time up to hundreds of milliseconds. Ten battery modules are designed to operate independently through 10 magnetic contactor (MC) switches so as to produce toroidal magnetic field with various amplitudes and waveforms. During the initial start-up experiments of VEST, the modulation capability of toroidal magnetic field is successfully verified, showing possibility of its versatile utilization on various experimental topics in the future.