The present invention provides cancellation of cogging torque of a permanent magnet electrical machine using two sets of magnetic elements, one set is mechanically coupled to the stator with the other set being mechanically coupled to the rotor of the machine. At least one of the two sets has permanent...http://www.google.ca/patents/US7737596?utm_source=gb-gplus-sharePatent US7737596 - Anti-cogging apparatus for permanent magnet electrical machines
