Patent ID: 8614617

Claim:
A reactor, comprising: an air-core coil formed by winding an elongated conductive member; and a core portion that covers both ends and an outer circumference of said air-core coil, wherein a ratio t/W of a length t of said elongated conductive member in a radial direction of said air-core coil to a length W of said elongated conductive member in an axial direction of said air-core coil is no more than 1, wherein one surface of said core portion that opposes one end of said air-core coil and one other surface of said core portion that opposes one other end of said air-core coil are parallel at least in regions covering the coil ends, wherein a circumferential direction surface of said elongated conductive member forming said air-core coil is perpendicular relative to the one surface of said core portion, and wherein a ratio R/W of a radius R from a center to an outer circumference of said air-core coil to a length W of said elongated conductive member in the axial direction of said air-core coil is 2 to 4; and wherein projections protruding to said air-core coil are formed at positions, facing an air-core part of said air-core coil, on an upper face and a lower face of said core portion, said projections being formed so as to satisfy: 0 <a≦W/ 3 and r >√( A 2 +( W/ 2) 2 ) wherein r is defined as the radius of said air-core part of said air-core coil, a is defined as the height from a core surface, opposing a coil end, of said projection, and A is defined as the radius of a projection bottom surface.