Device for a current limiter and a current limiter comprising said device

A device for a current limiter, the device comprising:

• at least one coil assembly adapted to carry a current, the coil assembly comprising:
• a first coil, comprising a first superconducting element, adapted to carry a first portion of said current;
• a second coil, comprising a second superconducting element adapted to carry a second portion of said current;
• and
• cooling means for cooling the first and second superconducting elements below their critical temperatures,
• wherein said first and second coils are arranged such that when said first and second superconducting elements are each in a superconducting state and said coil assembly carries said current, a magnetic field generated by said first portion of said current in said first coil is substantially cancelled by a magnetic field generated by said second portion of said current in said second coil;
• wherein said coil assembly further comprises a former for supporting said first and second coils, said former being adapted to thermally couple said first and second coils to said cooling means;
• and
• wherein said device is adapted such that, in use, when said first and second coils are thermally coupled to said cooling means, said first and second superconducting elements are maintained at different temperatures so that the first superconducting element has a lower critical current than the second superconducting element for undergoing a transition from a superconducting state to a normally conducting state.

A device for a current limiter, the device comprising:

• at least one coil assembly adapted to carry a current, the coil assembly comprising:
• a first coil, comprising a first superconducting element, adapted to carry a first portion of said current;
• a second coil, comprising a second superconducting element, adapted to carry a second portion of said current;
• and
• a former for supporting said first and second coils, wherein said former is adapted to thermally couple said first and second coils to cooling means for cooling said first and second superconducting elements to temperatures below their critical temperatures,
• the first superconducting element having a smaller cross-sectional area than the second superconducting element,
• wherein, in use, the first superconducting element has a lower critical current than the second superconducting element for undergoing a transition from a superconducting state to a normally conducting state.