マグネット電源の基礎

―パワーエレクトロニクスの基礎解説―

抄録

This article summarizes the basics of power supply systems for magnets, especially the basic theory of AC/DC power converter systems for superconducting magnets. In order to control both excitation and demagnetization of the magnet, the power converter requires alternative DC voltage control capability. Since the current path from the converter system to the magnet is constant, the switching device requires reverse blocking capability to withstand reverse voltage. Thyristor converters are widely used as power converter systems for fusion magnets and accelerator magnets. The thyristor converter enables both excitation and demagnetization of the magnet by controlling the firing angle. The voltage source converter becomes a feasible option for magnet power supply systems. However, since the direction of DC voltage is constant, the power supply system requires a DC chopper in order to control the applied voltage of the magnet in both directions. The power flow between the threephase AC system and a voltage source converter is fundamentally determined by the voltage phase difference between the AC system and the converter.