Patent ID: 6885129

Claim:
An automotive alternator comprising: a field rotor provided with: a field coil; and a Lundell-type core having: a cylindrical portion on which said field coil is installed; yoke portions disposed so as to extend radially outward from axial end portions of said cylindrical portion; and claw-shaped magnetic pole portions disposed so as to extend axially from radial edge portions of said yoke portions so as to surround said field coil; and a stator composed of a laminated core and an armature coil disposed facing an outer circumference of said claw-shaped magnetic pole portions, wherein a ratio (R 2 /R 1 ) between an outer radius R 2 of said cylindrical portion and an outer radius R 1 of said Lundell-type core is in a range from 0.50 to 0.54, and a ratio (Lc/Lp) between an axial length Lc of said laminated core and an axial length Lp of said Lundell-type core is in a range from 0.55 to 0.70.