Patent ID: 8588875

Claim:
A superconducting fault current-limiter comprising: a superconducting element, the superconducting element being configured to at least partially resistively or inductively limit a fault current passing therethrough; multiple, series connected, variable-impedance shunts electrically connected in parallel with the superconducting element, the multiple, series connected, variable-impedance shunts defining a variable impedance element connected in parallel with the superconducting element and configured to present a first impedance during a superconducting state of the superconducting element and a second impedance during a recovery transition of the superconducting element from a normal reisitive state to the superconducting state, the superconducting element transitioning from the superconducting state to the normal resistive state responsive to the fault current, and responsive thereto the variable impedance element transitions from the first impedance to the second impedance, the second impedance of the variable impedance element being a lower impedance than the first impedance and the transitioning of the variable impedance element from the first impedance to the second impedance facilitates current flow through the multiple, series connected, variable-impedance shunts during recovery transition of the superconducting element from normal resistive state to superconducting state, thereby facilitating recovery of the superconducting element under load; wherein each variable-impedance shunt of the multiple, series connected, variable-impedance shunts comprises a variable-impedance shunt coil at least partially surrounding a respective saturatable core disposed separate from the superconducting element, where impedance through the variable-impedance shunt coil transitions from the first impedance to the second impedance with saturation of the respective saturatable core; and wherein each variable-impedance shunt of the multiple, series connected, variable-impedance shunts further comprises a respective fixed impedance in parallel with the variable-impedance shunt coil, and wherein at least two saturatable cores of the multiple, series connected, variable-impedance shunts comprise a different saturation characteristic.