Patent ID: 7649721

Claim:
A fault current limiting arrangement, comprising: a primary circuit for current to be limited in the event of a fault, a core having a primary winding forming part of the primary circuit; a coil coupled with the core, and a DC current supply for the coil, to provide a bias level of flux in the core; an auxiliary winding coupled with the core, wherein the core comprising first and second arms, the second arm being thicker than the first arm, the primary winding being wound around the first arm, and the auxiliary winding being wound around the second arm; and an auxiliary current source for the auxiliary winding, means to adjust the output of the auxiliary current source in response to changes at the primary winding to apply control to the primary winding by control of the flux within the primary winding, wherein the auxiliary current source is operable to control the auxiliary current to maintain substantially constant flux within the primary winding, during use, except during fault conditions.