THREE-PHASE ELECTRIC MOTOR WITH A LOW DETENT TORQUE

• US 20120104905A1
• Filed: 05/11/2010
• Published: 05/03/2012
• Est. Priority Date: 05/11/2009
• Status: Active Application

• Current Assignee: MMT SA
• Original Assignee: Moving Magnet Technologies
• Inventors: Prudham, Daniel, Pfister, Pierre-Daniel, Richard, Thibaut
• Granted Patent: US 9,515,539 B2
• Time in Patent Office: Days
• US Class Current: 310/68.B
• CPC Class Codes: H02K 1/146 consisting of a generally annular yoke with salient poles
• CPC Class Codes: H02K 1/2781 Magnets shaped to vary the mechanical air gap between the magnets and the stator
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems

Abstract

The disclosure relates to a three-phase electric motor that uses high magnetic energy permanent magnets and that has a low detent torque. The motor consists of a rotor with N pairs of poles and of a stator portion with teeth extending radially from an annular gear. The teeth have windings and the ends thereof comprise an arc of circle, the middle of which is located on a radius R1 and two sides defining an alpha angle, the vertex of which is located on a radius R2. The ratio R2/R1 is substantially equal to (1+/−0.26/N), and the alpha angle is between 110 and 135°.

Claims

1. A three-phase electric motor comprising a rotor that has N pairs of poles and the stator portion, having 3×

N teeth extending radially from an annular gear, the stator portion being excited by electrical windings, each tooth having at its end an arc of circle and two sides, a middle of the arc of circle being situated on a first radius (R1) and the two sides defining an angle alpha, the vertex of which is situated on a second radius (R2), the first radius (R1) and the second radius (R2) defining a ratio R2/R1 substantially equal to (1+/−

0.26/N), and in that the angle alpha is between 110 and 135°

.

2. The three-phase electric motor as claimed in claim 1, wherein characterized in that the rotor exhibits a normal induction and a tangential induction each containing less than 20% of harmonic 3, less than 2% of harmonic 5 and less than 2% of harmonic 7.

3. The three-phase electric motor as claimed in claim 1, wherein each end of the tooth has a convex shape.

4. The three-phase electric motor as claimed in claim 1, wherein each end of the tooth has a concave shape.

5. The three-phase electric motor as claimed in claim 1, wherein the stator has a winding on each of the teeth.

6. The three-phase electric motor as claimed in claim 1, wherein the stator has a winding for one tooth in every two.

7. The three-phase electric motor as claimed in claim 1, wherein the windings are wound separately then inserted into the stator.

8. The three-phase electric motor as claimed in claim 1, wherein the rotor includes a magnet injected onto a yoke made of a ferromagnetic material.

9. The three-phase electric motor as claimed in claim 1, wherein the rotor includes four tiles, made of an anisotropic material and assembled on a yoke made of a ferromagnetic material.

10. The three-phase electric motor as claimed in claim 1, wherein the rotor includes a ring magnet made of an isotropic material.

11. The three-phase electric motor as claimed in claim 1, wherein the rotor includes a ring magnet having a polar anisotropy.

12. The three-phase electric motor as claimed in claim 1, wherein the stator includes a stack of thin plates.

13. The three-phase electric motor as claimed in claim 1, further comprising position detection elements acting with the rotor.

14. A three-phase electric motor comprising:

a rotor including magnetic poles;

a stator including radially extending teeth wrapped by conductive windings, a distal end of each tooth being no larger than the section of each tooth wrapped by the windings, and the distal end of each tooth facing the rotor having an arcuate shape; and

energy used by the magnetic poles being from 6 to 40 MGOe, but the stator teeth defining less than 60% of the available circular surface area.

15. The three-phase electric motor as claimed in claim 14, wherein residual torque is cancelled for each of the teeth individually.

16. The three-phase electric motor as claimed in claim 14, wherein the arcuate shape of the distal end of each tooth is convex.

17. The three-phase electric motor as claimed in claim 14, wherein the arcuate shape of the distal end of each tooth is concave.

18. The three-phase electric motor as claimed in claim 14, wherein the rotor exhibits a normal induction and a tangential induction each containing less than 20% of harmonic 3, less than 2% of harmonic 5 and less than 2% of harmonic 7.

19. The three-phase electric motor as claimed in claim 14, wherein the rotor includes four tiles, made of an anisotropic material and assembled on a yoke made of a ferromagnetic material.

20. A three-phase electric motor comprising:

a rotor including a ring magnet;

a stator including N pairs of radially extending poles with conductive windings located adjacent the poles;

each stator pole having a point which collectively defines a circle, a middle of the circle having a first radius R1, two sides of each stator pole defining an angle the vertex of which is on a second radius R2, the radii defining a ratio R2/R1 being substantially equal to;

1+/−

0.26/N,

 

and the angle is between 110° and

135°

;

the rotor exhibiting a normal induction and a tangential induction each containing less than 20% of harmonic 3, less than 2% of harmonic 5 and less than 2% of harmonic 7; and

residual torque being cancelled for each of the stator poles individually to avoid a torque compensation between two or more of the stator poles.