Patent ID: 8217544

Claim:
A motor-generator comprising: a stator including an annular stator core and stator windings wound on the stator core; an annular inner rotor located radially inward of the stator core with a first air gap formed between the inner rotor and the stator core; and an annular outer rotor located radially outward of the stator core with a second air gap formed between the outer rotor and the stator core, wherein each of the inner and outer rotors is made of a soft magnetic material or magnetic steel, the stator core consists of a plurality of stator core segments each of which is in the form of a tooth, the stator windings are wound on the stator core in a continuous distributed winding manner at a predetermined winding pitch, the outer rotor consists of a plurality of outer rotor segments each of which is magnetically polarized to have opposite polarities on opposite circumferential ends thereof, and each of the outer rotor segments is offset from the inner rotor by a predetermined electrical angle that corresponds to the winding pitch of the stator windings.