Fault current limiters (FCL) with the cores saturated by superconducting coils

A current limiting device (30, 40, 50, 60) comprising for each phase of an AC supply a closed magnetic core (31) of reduced volume and mass having first and second pairs of opposing limbs (32 a , 32 b ; 33 a , 33 b), and at least one AC coil (35 a , 35 b) enclosing opposing limbs (33 a , 33 b) of the magnetic core (31) and adapted for series connection with a load. A superconducting DC bias coil (34) encloses a limb) (32 a , 32 b) of the magnetic core (31) for saturating each of the opposing limbs (33 a , 33 b) in opposite directions by the bias coil (34). Under fault conditions, the AC flux in at least one limb counteracts the DC bias flux, bringing the limb out of saturation. Preferably, current is reduced in the DC bias coils thus bringing both opposing limbs of the core out of saturation.