US 7,321,176 B2
Multi pole electrical machine with reduced cogging force
Thomas Strothmann, Wallenhorst (Germany)
Assigned to Invacare Corporation, Elyria, Ohio (US)
Filed on Aug. 21, 2002, as Appl. No. 10/225,469.
Application 10/225469 is a continuation of application No. 09/553522, filed on Apr. 20, 2000, abandoned.
Prior Publication US 2003/0038557 A1, Feb. 27, 2003
Int. Cl. H02K 21/12 (2006.01)
U.S. Cl. 310—156.15  [310/156.36; 310/216] 12 Claims
OG exemplary drawing
 
1. A multiple phase electric machine comprising:
at least three stator segments, each segment having:
M stator poles, wherein M is an integer number equal to or greater than 3;
a first distance between adjacent stator poles; and
at least one stator pole for each phase of the multiple phase electric machine, including a first stator pole electrically connected to a first electric phase of the machine, a second stator pole electrically connected to a second phase of the electrical machine, and a third stator pole electrically connected to a third phase of the electrical machine;
a number of rotor segments equal to the number of stator segments, each rotor segment being associated with a unique stator segment and having:
N permanent magnet rotor poles, wherein N is an integer number greater or less than M, wherein pairs of successive permanent magnet rotor poles define a magnetic period, and wherein the ratio of M to N/2 is a non integer number; and
a second distance between adjacent permanent magnet rotor poles; wherein the second distance is greater or less than the first distance between adjacent stator poles; and
the stator segments forming a generally circular stator part and
the rotor segments forming a generally circular rotor part wherein the generally circular rotor part is external to the generally circular stator part.