Patent ID: 7633287

Claim:
A current sensor which measures a primary current by an output of a secondary winding, comprising: a core which has a penetration portion in a central portion thereof and collects magnetic flux generated by the primary current passing through a primary conductor, the primary conductor being disposed while penetrating through the central portion; and a secondary winding which is wound in a toroidal form around a body portion of the core and detects a change of the magnetic flux in the core, the core further including: a plurality of magnetic material portions made of a magnetic material and configured to divide the core in a circumferential direction of the core; and a plurality of non-magnetic material portions made of a non-magnetic material and configured to divide the core in the circumferential direction of the core; the magnetic material portions and the non-magnetic material portions being alternately arranged over a whole circumference of the core, and the secondary winding being wound around the body portion of the core under conditions in which each core cross section intersects the magnetic material portion and the non-magnetic material portion, each core cross section being of a cutting plane in the core and including a cut end surface of each conductor along a direction in which each conductor constituting the secondary winding is extended, and a ratio of a magnetic material portion cross-sectional area of the magnetic material portion to a non-magnetic material portion cross-sectional area of the non-magnetic material portion at the core cross section is kept constant in each core cross section.