Synchronous machine design and manufacturing
Synchronous motors according to the invention operate at higher efficiency, with lower cost, reduced mass and reduced cogging. Magnet dimensions are selected that reduce cogging forces to a negligible amount even though there are fewer slots than normal. Optionally, it is possible to use non-overlapping windings with deeper and open slots. The approach is applicable to both rotary and linear motors and motors using either permanent magnets or electromagnets in the field structure. It is particularly relevant to linear or rotary motors that have a large air gap, and to small motors that must deliver a high ratio of thrust or torque to motor mass.
1. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. extensions are absent from tips of a plurality of said poles,
B. said coil windings comprise a succession of coil windings, none of which overlaps a next immediate coil winding in the succession,
C. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
D. a relative dimension of pales to teeth, along a relative direction of motion of the poles to the teeth, is selected so as in substantially null a lowest harmonic term of a cogging force that results from interaction of the magnetic field and the armature and that is proportional to a square of the magnetic field strength, and
E. a half-pole is provided at the end of at least one field structure.
2. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
B. each of a plurality of said coil windings does not overlap an adjacent coil winding disposed in the slots,
C. a relative dimension of poles to teeth, along a direction of motion of the poles relative to the teeth, is selected so as to minimize a lowest harmonic term of a force that results from interaction of the magnetic field and the armature that is proportional to a square of the magnetic field strength, and
D. a half-pole is provided at the end of at least one field structure.
3. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. extensions are absent from tips of a plurality of said poles,
B. said coil windings comprise a succession of coil windings, none of which overlaps a next immediate coil winding in the succession,
C. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
D. a relative dimension of poles to teeth, along a relative direction of motion of the poles to the teeth, is selected so as to substantially null a lowest harmonic term of a cogging force that results from interaction of the magnetic field and the armature and that is proportional to a square of the magnetic field strength, and
E. the further improvement wherein the poles define a magnetic field of length λ, and wherein the poles of at least one field structure are arranged in a Halbach Array, and wherein, for those poles of that structure generating a magnetic field perpendicular to the air gap, a ratio of magnet length to λ/2 is substantially 0.35:1 or 0.67:1.
4. In a synchronous motor comprising one or more field structure and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. extensions are absent from tips of a plurality of said poles,
B. said coil windings comprise a succession of coil windings, none of which overlaps a next immediate coil winding in the succession,
C. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
D. a relative dimension of poles to teeth, along a relative direction of motion of the poles to the teeth, is selected so as to substantially null a lowest harmonic term of a cogging force that results from interaction of the magnetic field and the armature and that is proportional to a square of the magnetic field strength, and
E. the further improvement wherein the poles define a magnetic field of wavelength λ, and wherein a ratio of magnet length along the relative direction of motion to λ/2 is substantially 0.77:1 or 0.45:1.
5. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. extensions are absent from tips of a plurality of said poles,
B. said coil windings comprise a succession of coil windings, none of which overlaps a next immediate coil winding in the succession,
C. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
D. a relative dimension of poles to teeth, along a relative direction of motion of the poles to the teeth, is selected so as to substantially null a lowest harmonic term of a cogging force that results from interaction of the magnetic field and the armature and that is proportional to a square of the magnetic field strength, and
E. the further improvement wherein a pole at the end of at least one field structure is arranged so as to minimize a third force harmonic between the field structure and the armature without increasing a sixth harmonic therebetween.
6. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. extensions are absent from tips of a plurality of said poles,
B. said coil windings comprise a succession of coil windings, none of which overlaps a next immediate coil winding in the succession,
C. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
D. a relative dimension of poles to teeth, along a relative direction of motion of the poles to the teeth, is selected so as to substantially null a lowest harmonic term of a cogging force that results from interaction of the magnetic field and the armature and that is proportional to a square of the magnetic field strength, and
E. wherein the poles of the field structures define a magnetic field of wavelength λ, the further improvement wherein relative dimensions of the field structure are selected in substantial accord with the following table:
Parameter
Dimension
Wavelength
60
Magnetic gap
4
Length of periodic magnets
23
Height of periodic magnets
5
Length of end magnet
14
Height of end magnets
4
Spacing between end magnets and neighbor-
11
ing magnet.
7. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
B. each of a plurality of said coil windings does not overlap an adjacent coil winding disposed in the slots,
C. a relative dimension of poles to teeth, along a direction of motion of the poles relative to the teeth, is selected so as to minimize a lowest harmonic term of a force that results from interaction of the magnetic field and the armature that is proportional to a square of the magnetic field strength, and
D. the further improvement wherein the poles define a magnetic field of length λ, and wherein the poles of at least one field structure are arranged in a Halbach Array, and wherein, for those poles of that structure generating a magnetic field perpendicular to the air gap, a ratio of magnet length to λ/2 is substantially 0.35:1 or 0.67:1.
8. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
B. each of a plurality of said coil windings does not overlap an adjacent coil winding disposed in the slots,
C. a relative dimension of poles to teeth, along a direction of motion of the poles relative to the teeth, is selected so as to minimize a lowest harmonic term of a force that results from interaction of the magnetic field and the armature that is proportional to a square of the magnetic field strength, and
D. wherein the poles define a magnetic field of wavelength λ, and wherein a ratio of magnet length along the relative direction of motion to λ/2 is substantially 0.77:1 or 0.45:1.
9. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
B. each of a plurality of said coil windings does not overlap an adjacent coil winding disposed in the slots,
C. a relative dimension of poles to teeth, along a direction of motion of the poles relative to the teeth, is selected so as to minimize a lowest harmonic term of a force that results from interaction of the magnetic field and the armature that is proportional to a square of the magnetic field strength, and
D. the further improvement wherein a polo at the end of at least one field structure is arranged so as to minimize a third force harmonic between the field structure and the armature without increasing a sixth harmonic therebetween.
10. In a synchronous motor comprising one or more field structures and one or more armatures, the field structures having poles for generating a magnetic field and the armatures having teeth with slots therebetween and coil windings disposed in those slots, the improvement wherein
A. each of a plurality of said coil windings are pre-wound prior to being disposed in said slots,
B. each of a plurality of said coil windings does not overlap an adjacent coil winding disposed in the slots,
C. a relative dimension of poles to teeth, along a direction of motion of the poles relative to the teeth, is selected so as to minimize a lowest harmonic term of a force that results from interaction of the magnetic field and the armature that is proportional to a square of the magnetic field strength, and
D. wherein the poles of the field structures define a magnetic field of wavelength λ, the further improvement wherein relative dimensions of the field structure are selected in substantial accord with the following table:
Parameter
Dimension
Wavelength
60
Magnetic gap
4
Length of periodic magnets
23
Height of periodic magnets
5
Length of end magnet
14
Height of end magnets
4
Spacing between end magnets and neighbor-
11
ing magnet.