Synchronous machine design and manufacturing

• US 20030107289A1
• Filed: 10/01/2002
• Published: 06/12/2003
• Est. Priority Date: 10/01/2001
• Status: Active Grant

• Current Assignee: Rockwell Automation, Inc.
• Original Assignee: Magnemotion Incorporated (Rockwell Automation, Inc.)
• Inventors: Clark, Tracy M., Thornton, Richard D.
• Granted Patent: US 6,917,136 B2
• Time in Patent Office: Days
• US Class Current: 310/216
• CPC Class Codes: H02K 1/08 Salient poles
• CPC Class Codes: H02K 21/16 having annular armature cores with salient poles with homopolar co-operation H02K21/20
• CPC Class Codes: H02K 2213/03 Machines characterised by numerical values, ranges, mathematical expressions or similar information
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
• CPC Class Codes: H02K 41/031 of the permanent magnet type

Abstract

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.

Claims

1. In a synchronous motor comprising one or more field structures and one or more armatures, the field structure having poles defining a magnetic field of wavelength λ

and the armature having teeth with slots therebetween and coil windings wound in those slots, the improvement wherein a ratio of number of teeth to wavelength is 3;

1 and wherein the poles and teeth are dimensioned with respect to one another so as to minimize cogging.

2. In a synchronous motor according to claim 1, the further improvement wherein extensions are absent from tips of a plurality of teeth.

3. In a synchronous motor according to any one of claims 1 and 2, the further improvement wherein one or more poles comprise permanent magnets.

4. In a synchronous motor according to any one of claims 1 and 2, the further improvement wherein the poles of at least one field structure are arranged in a Halbach Array.

5. In a synchronous motor according to any one of claims 1 and 2, the further improvement wherein half-poles are provided at the end of at least one field structure.

6. In a synchronous motor according to any one of claims 1 and 2, the further improvement comprising a succession of said windings wound in said slots such that at least one of those coil windings does not overlap a next immediate coil winding in the succession.

7. In a synchronous motor according to claim 6, the further improvement wherein each coil winding is wound around a respective tooth.

8. In a synchronous motor according to claim 6, the further improvement wherein a ratio of number of coil windings to wavelength is 3:

1.

9. In a synchronous motor according to any one of claims 1 and 2, the further improvement wherein the field structure and armature are arranged to define a linear synchronous motor.

10. In a synchronous motor according to any one of claims 1 and 2, the further improvement wherein the field structure and armature are arranged to define a rotary synchronous motor.

11. In a synchronous motor comprising one or more field structures and an armature, the field structures having magnetic poles and the armature having teeth with slots therebetween and coil windings wound in those slots, the improvement wherein the poles and teeth are dimensioned with respect to one another so as to minimize selected force harmonics, those selected force harmonics being ones that are proportional to a square of pole strength.

12. In a synchronous motor according to claim 11, the further improvement wherein the poles defining a magnetic field of wavelength λ

, the further improvement wherein a ratio of magnet length to λ

/2 is substantially 0.77;

1 or 0.45;

1

13. In a synchronous motor according to any one of claims 11 and 12, the further improvement wherein the poles defining a magnetic field of wavelength X, the further improvement wherein a ratio of number of teeth to wavelength is 3:

1.

14. In a synchronous motor according to any one of claims 11 and 12, the further improvement wherein extensions are absent from tips of a plurality of tips.

15. In a synchronous motor according to any one of claims 11 and 12, the further improvement wherein the poles and teeth are dimensioned with respect to one another so as to minimize a sixth force harmonic therebetween.

16. In a synchronous motor comprising one or more field structures and one or more armatures, the field structure having poles defining a magnetic field and the armature having teeth with slots therebetween and coil windings wound in those slots, the improvement wherein poles at the end of at least one field structure are arranged so as to minimize a third force harmonic between the field structure and the armature without increasing a sixth harmonic therebetween.

17. In a synchronous motor according to claim 16, wherein the poles of the field structure define a magnetic field of wavelength λ

, the further improvement wherein relative dimensions for the field structure are selected in substantial accord with the following table;