A total of three permanent magnets, installed in a rotor core closely to an outer cylindrical surface of the rotor core, are disposed at predetermined angular pitches in the circumferential direction of the rotor core. All of the permanent magnets are magnetized in such a manner that the direction of...http://www.google.com.tw/patents/US7105971?utm_source=gb-gplus-share專利 US7105971 - Permanent-magnet rotor for an inner rotor type electric rotary machine and magnet-saving type rotor for a synchronous motor
