Patent ID: 8680738

Claim:
A universal motor comprising: a stator and a rotor rotatably installed in the stator, wherein the rotor comprises a rotor core and rotor windings wound on the rotor core, wherein the stator comprises a stator core having a yoke, n primary poles with windings wound thereon and n auxiliary poles, the primary poles and auxiliary poles being alternately arranged at the radially inner side of the yoke in a circumferential direction thereof, the auxiliary poles being without windings wound thereon or with additional windings wound thereon, the number of turns of the additional windings being less than that of the windings wound on the primary poles; and wherein when the windings are electrified, n primary magnetic poles and n auxiliary magnetic poles are formed at the primary poles and auxiliary poles respectively and 2n magnetic circuits are formed, each primary magnetic pole has the same polarity and each auxiliary magnetic pole has the same polarity which is opposite the polarity of the primary magnetic poles, n being an integer greater than 1, each of the magnetic circuits passing through a primary magnetic pole and an adjacent auxiliary magnetic pole and corresponding portions of the rotor and yoke such that the length of the magnetic circuit is reduced and the torque produced by the motor is increased.