US 4,672,253 AGranted

Permanent magnet electrical machine with reduced cogging

AssigneeHitachi, Ltd.

InventorsFumio Tajima, Hiroshi Katayama, Kunio Miyashita, Teizo Tamura, Kenichi Hironaka, Takuro Kawano, Yosimi Sekita, Kouichi Saito, Akira Tamura

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Abstract

A permanent magnet electric machine such as, for example, a motor or generator, including a permanent magnet field member, an armature having salient magnetic poles and armature windings. A greatest common division of the number of magnetic poles of the field member and the salient magnetic poles having the armature windings differs from the number of magnetic poles. A group of grooves is formed between the salient magnetic poles having an interval of 2/3M.pi., with M being an integer which is not a multiple of three. To reduce the occurrence of cogging torque, auxiliary grooves are provided on the surface of the salient poles at positions which are spaced apart from positions of the grooves by (.pi./3)K+(.pi./6), in terms of electrical angle, with K being an integer.

Claims19

Dependent claims

A permanent magnet electric machine comprising:

a field member having at least one pair of magnetic poles, each including a permanent magnet;
and
an armature member disposed in opposition to said field member having a plurality of salient winding poles around which armature widings are wound;
a greatest common divisor of the number of said magnetic poles of said field member and a number of said salient magnet poles differing from the number of the magnetic poles of said field member;
winding grooves formed by two adjacent salient winding poles at an electrical angular interval of 2/3P.pi., where P is a number of pairs of the magnetic poles of said field member which is not a multiple of three;
and
wherein each salient pole is provided in a surface thereof facing the magnetic poles of said field member, with auxiliary grooves at positions of the winding grooves in terms of an electrical angle by (.pi./3)K+(.pi./6) where K is an integer and at positions spaced by (.pi./12)L from the respective winding and auxiliary grooves in terms of an electrical angle, where L is an odd integer.

4 more elements

A permanent magnet motor comprising:

a field member of a circular configuration having at least one pair of magnetic poles, each including a permanent magnet;
an armature member disposed in opposition to and coaxial with said field member and having a plurality of salient winding poles, around which armature windings are wound, and auxiliary salient poles so provided that each auxiliary salient pole is interposed between two adjacent salient winding poles;
a greatest common divisor of the number of the magnetic poles of said field member and the number of the salient winding poles differs from the number of the magnetic poles of said field member;
a first group of windings grooves, on one side of the auxiliary salient poles, and a second group of winding grooves on the other side thereof, are formed by said salient winding poles, in which the winding grooves of each group are arranged at an interval, in terms of an electrical angle, of 2/3P.pi. with P being a number of pairs of magnetic poles of the field member which is not a multiple of three, and in which the first group of the winding grooves is shifted by .pi./12L, wherein L is an odd integer in terms of an electrical angle;
and
wherein each of said salient winding poles has auxiliary grooves on the surface opposite to said field member at positions which are spaced from a position of said grooves, in terms of an electrical angle, by (.pi./3)K+(.pi./6)K with K being an integer.

3 more elements

Dependencies are inferred from the claim text.