Coil unit of toroidal magnetic field

Toroidal magnetic coil groups comprise all of conductors such as coils intersecting toroidal magnetic fields which reduce a transient inpedance for abruptly reducing or increasing electric current and equivalent primary inpedance reducing coils for abruptly reducing current upon protection from quenching in the toroidal magnetic field coils. Primary coil current is transferred to secondary coils by using protection coils as secondary coils, so that the current in the primary coils (that is, toroidal magnetic field coils) can be attenuated earlier than the attenuation of the total magnetic energy, to ensure protection operation from quenching. Then, occurrence of quenching phenomenon can be avoided efficiently, thereby enabling to attain remarkable cost down and simplification of systems. (N.H.)