Electromagnetic rotary machine having magnetic bearing

• US 5,955,811 A
• Filed: 02/08/1996
• Issued: 09/21/1999
• Est. Priority Date: 02/09/1995
• Status: Expired due to Fees

• Current Assignee: Akira Chiba, Tadashi Fukao
• Original Assignee: Akira Chiba, Seiko Instruments Incorporated (Seiko Group), Tadashi Fukao
• Inventors: Chiba, Akira, Fukao, Tadashi, Maejima, Yasushi
• Primary Examiner(s): ENAD, ELVIN GENARGUE
• Application Number:
  US08/598,375
• Time in Patent Office: 1,321 Days
• Field of Search: 310/211, 310/254, 310/90.5, 310/261, 310/179, 310/258, 310/114
• US Class Current: 310/211
• CPC Class Codes: F16C 2360/45 Turbo-molecular pumps in general F04D19/04
• CPC Class Codes: F16C 2380/26 Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators in general H02K
• CPC Class Codes: F16C 32/0459 Details of the magnetic circuit
• CPC Class Codes: F16C 32/0491 with electromagnets acting in axial and radial direction, e.g. with conical magnets
• CPC Class Codes: F16C 32/0493 integrated in an electrodynamic machine, e.g. self-bearing motor
• CPC Class Codes: H02K 17/165 characterised by the squirrel-cage or other short-circuited windings
• CPC Class Codes: H02K 7/09 with magnetic bearings

Abstract

A high speed electromagnetic rotating machine is arranged to avoid heat generation due to mutual inductance between a stator and rotor and has a stator provided with drive windings for generating a rotating magnetic field to rotate the rotor and position control windings fitted to the stator for generating a magnetic field having a different number of poles than that of the drive windings for controlling the axial or radial position of the rotor when an electric current sufficient to unbalance the magnetic field applied to the rotor by the drive windings is supplied to the position control windings. The rotor has a cage conductors interconnected to form a plurality of closed circuits mounted to the rotor, the closed circuits having a number of poles set so that there is no mutual inductance between the position control windings and the cage conductors. The cage conductors are connected by circumferentially-divided end rings rigidly connected by a retaining ring or by axially divided end rings directly connected to the rotor shaft. In one embodiment, the cage conductors are arranged in four-pole closed circuits, the drive windings have four poles, and the position control windings have two poles. In an alternative embodiment, the cage conductors may be arranged in two-pole closed circuits, the drive windings have two poles and the position control windings have four poles.

Claims

1. An electromagnetic rotary machine driven by an electromagnetic induction between a stator and a rotor and having a magnetic bearing, the stator including a stator core and stator windings wound around the stator core to produce a torque for driving the rotor, and the rotor including a rotor core, the electromagnetic rotary machine comprising:

position control windings wound around the stator core for exerting at least one of a radial magnetic force and an axial magnetic force on the rotor for adjusting the position of the rotor in at least one of a radial direction and an axial direction, the number of poles of the position control windings being different from the number of poles of the stator windings; and

cage conductors mounted to the rotor core and having end rings disposed at opposite ends of the cage conductors, the end rings being divided in one of a circumferential and an axial direction for connecting selected ones of the conductors to form a plurality of closed circuits;

wherein the number of poles of the closed circuits is set such that mutual inductance between the position control windings and the cage conductors is zero.

2. An electromagnetic rotary machine according to claim 1;

wherein selected cage conductors are connected in plural four-pole closed circuits, the stator windings have four poles, and the position control windings have two poles.

3. An electromagnetic rotary machine according to claim 1;

wherein selected cage conductors are connected in plural two-pole closed circuits, the stator windings have two poles, and the position control windings have four poles.

4. An electromagnetic rotary machine according to claim 1;

wherein the end rings are divided in a circumferential direction so as to form the closed circuits and are interconnected by annular retainer rings.

5. An electromagnetic rotary machine according to claim 1;

wherein the rotor includes a rotary shaft and the end rings are divided in an axial direction and are mounted directly onto the rotary shaft.

6. An electromagnetic rotary machine according to claim 1;

wherein the cage conductors have magnetic poles formed by a plurality of parallel conductors.

7. An electromagnetic rotary machine according to claim 1;

wherein the rotor core is skewed.

8. An electromagnetic rotary machine according to claim 1;

wherein the rotor core and the stator core have axially inclined peripheral surfaces and the position control windings exert an axial magnetic force on the rotor.

9. An electromagnetic rotary machine according to claim 1;

wherein the rotor core has ends axially offset from ends of the stator core and the position control windings exert an axial magnetic force on the rotor.

10. An electromagnetic rotating machine driven by an electromagnetic action between a stator and a rotor, the machine comprising:

a stator having one or more drive windings for generating a rotating magnetic field for rotatably driving the rotor;

one or more position control windings fitted to the stator for generating a magnetic field having a different number of poles than that of the one or more drive windings, whereby a magnetic force acts on the rotor by supplying one or more of the position control windings with an electric current sufficient to unbalance the magnetic field applied to the rotor by the drive windings so as to control at least one of the axial and radial position of the rotor within the stator; and

a plurality of cage conductors selectively interconnected to form a plurality of closed circuits mounted to the rotor, the closed circuits having a number of poles set so that there is no mutual inductance between the position control windings and the cage conductors when the rotor is centrally disposed within the stator.

11. An electromagnetic rotating machine according to claim 10;

further comprising end rings for connecting the cage conductors in the plurality of closed circuits, and a retaining ring for rigidly connecting the end rings to each other, wherein the end rings each comprise a conductive material having an arcuate shape provided with slots for receiving selected cage conductors which are to be short-circuited to each other to form the closed circuits and an arcuate recess for receiving the retaining ring, and wherein a plurality of end caps equal to the number of closed circuits is arranged at each end of the rotor for receiving the cage conductors to be short circuited to each other to form the closed circuits.

12. An electromagnetic rotating machine according to claim 10;

further comprising end rings for connecting the cage conductors in the plurality of closed circuits, and wherein the rotor comprises a shaft extending through the stator, the end rings each comprise a conductive material provided with slots for receiving selected cage conductors which are to be short circuited to each other to form the closed circuits, and a plurality of end caps equal to the number of closed circuits are rigidly connected to the shaft for receiving the cage conductors to be short circuited to each other to form the closed circuits.

13. An electromagnetic rotating machine according to claim 10;

wherein the cage conductors comprise four-pole closed circuits, the drive windings have four poles, and the position control windings have two poles.

14. An electromagnetic rotating machine according to claim 10;

wherein the cage conductors comprise two-pole closed circuits, the drive windings have two poles and the position control windings have four poles.

15. An electromagnetic rotating machine according to claim 10;

wherein the cage conductors have magnetic poles formed by a plurality of parallel conductors.

16. An electromagnetic rotating machine according to claim 10;

wherein the rotor core is skewed.

17. An electromagnetic rotating machine according to claim 10;

wherein the rotor and the stator have axially inclined peripheral surfaces and the position control windings exert an axial magnetic force on the rotor.

18. An electromagnetic rotating machine according to claim 10;

wherein the rotor has ends axially offset from ends of the stator and the position control windings exert an axial magnetic force on the rotor.