Fixed gain electromagnetic actuator and electromagnetic bearing incorporating same

• US 5,319,273 A
• Filed: 10/26/1992
• Issued: 06/07/1994
• Est. Priority Date: 10/26/1992
• Status: Expired due to Term

• Current Assignee: Perfect Galaxy International Limited
• Original Assignee: Satcon Technology Corporation
• Inventors: Eisenhaure, David B., Hockney, Richard L., Downer, James R.
• Primary Examiner(s): Voeltz, Emanual T.
• Assistant Examiner(s): TSO, EDWARD H
• Application Number:
  US07/967,251
• Time in Patent Office: 589 Days
• Field of Search: 310/90.5, 310/68 B, 318/632, 318/127, 318/128
• US Class Current: 310/90.5
• CPC Class Codes: F04D 29/058 magnetic; electromagnetic
• CPC Class Codes: F16C 2360/44 Centrifugal pumps
• CPC Class Codes: F16C 32/0444 Details of devices to control the actuation of the electromagnets
• CPC Class Codes: F16C 32/0457 Details of the power supply to the electromagnets
• CPC Class Codes: F16C 32/0463 with electromagnetic bias, e.g. by extra bias windings
• CPC Class Codes: F16C 32/048 with active support of two degrees of freedom, e.g. radial magnetic bearings
• CPC Class Codes: H02K 7/09 with magnetic bearings

Abstract

A fixed gain electromagnetic actuator for controlling the position of a body including at least two pair of a magnetically permeable pole spaced from the body, bias coils about each pole, separate control coils about each pole, a bias source for the bias coils providing a current in the bias coils producing a steady-state equal strength magnetic field on opposing sides of a body, and a control source for the control coils providing a current in the control coils for producing an increase in the magnetic field on one side of the body and a corresponding equivalent decrease in the magnetic field on the opposing side of the body to compensate for any external upsetting forces acting on the body.

Claims

1. A fixed gain electromagnetic actuator for controlling the position of a body comprising:

at least two pairs of opposing pole means spaced from the body for defining air gaps between the actuator and the body;

bias means for each pole means for establishing equal strength magnetic fields in the air gaps on opposing sides of the body;

separate control means for each pole means for controlling the position of the body;

a bias source for said bias means for providing a first current in said bias means for producing the equal strength magnetic fields in the air gaps on opposing sides of the body; and

a control source for said control means for providing a second current in said control means producing an increase in the equal strength magnetic field on one side of the body and producing a corresponding decrease in the equal strength magnetic field on the opposing side of the body to compensate for any external upsetting forces acting on the body.

2. The fixed gain electromagnetic actuator of claim 1 in which said bias means include a coil wound about each pole means.

3. The fixed gain electromagnetic actuator of claim 2 in which said bias coils wound about each pole of each pair of poles are wound in opposite directions.

4. The fixed gain electromagnetic actuator of claim 3 in which said bias coils for opposing pairs of poles are connected in series.

5. The fixed gain electromagnetic actuator of claim 1 in which said bias source is a low voltage d.c. power supply.

6. The fixed gain electromagnetic actuator of claim 1 in which said control means include a coil wound about each pole means.

7. The fixed gain electromagnetic actuator of claim 6 in which said control coils wound about each pole of each pair of poles are wound in opposite directions.

8. The fixed gain electromagnetic actuator of claim 7 in which said control coils for opposing pairs of poles are connected in series.

9. In an electromagnetic actuator for creating a fixed gain net force on a body, the improvement comprising:

at least two pairs of magnetic permeable poles spaced about the body defining air gaps between the actuator and the body, each pole of each pair wound with a control coil and a separate bias coil;

the control coils and the bias coils of one said pair of poles wound in the same direction;

the control coils and the bias coils of each opposing said pair of poles wound in opposite directions;

said bias coils of opposing pairs of poles connected in series; and

said control coils of opposing pairs of poles connected in series;

a bias source for said bias coils for producing a current in the bias coils for producing equal strength magnetic fields in the air gaps on opposing sides of the body; and

a control source for said control coils for providing a current in the control coils for producing an increase in the equal strength magnetic field on one side of the body and producing a corresponding equivalent decrease in the equal strength magnetic field on the opposing side of the body to compensate for any external forces acting on the body.

10. An electromagnetic bearing comprising:

an actuator including at least two pairs of opposing pole means spaced about a rotor for defining air gaps between the actuator and the rotor;

bias means for each pole means for establishing equal strength magnetic fields in the air gaps on opposing sides of the rotor;

separate control means for each pole means for controlling the position of the rotor;

a bias source for said bias means for providing a bias current in said bias means for producing equal strength magnetic fields in the air gaps on opposing sides of the rotor establishing a steady-state position for the rotor with respect to said pole means;

sensor means for detecting displacement of the rotor relative to said steady-state position; and

means, responsive to said sensor means, for correcting displacement of the rotor under loading conditions including a control current source for providing a control current in said control means producing an increase in the equal strength magnetic field on one side of the rotor and an automatic corresponding equivalent decrease in the equal strength magnetic field on the opposing side of the rotor, and means to selectively activate said current source.

11. The electromagnetic bearing at claim 10 in which said bias means include a coil wound about each pole means.

12. The electromagnetic bearing of claim 11 in which said bias coils wound about each pole of a pair of poles are wound in opposite directions.

13. The electromagnetic bearings of claim 12 in which said bias coils for opposing pairs of poles are connected in series.

14. The electromagnetic bearing of claim 10 in which said control means include a coil wound about each pole means.

15. The electromagnetic bearing of claim 14 in which said control coils wound about each pole of a pair of poles are wound opposite directions.

16. The electromagnetic bearing of claim 15 in which said control coils for opposing pairs of poles are connected in series.

17. An electromagnetic bearing for controlling the position of a body in one plane comprising:

four pairs of magnetic permeable poles spaced from the body defining air gaps between said poles and said body, each pair opposing another pair;

position sensor means for detecting the position of the body with respect to said poles;

a control coil wound about each pole and a separate bias coil wound about each pole, the control coils and the bias coils of one opposing pair of poles wound in the same direction, the control coils and bias coils of the other opposing pair of poles wound in the opposite direction;

said bias coils of each two pair of opposing poles connected in series and said control coils of each two pair of opposing poles connected in series;

a bias source interconnected with said bias coils for producing equal strength magnetic fields proximate each pair of poles;

position controller means, responsive to said position sensor means, for increasing the magnetic field proximate one pair and automatically reducing the magnetic field by an equivalent amount proximate an opposing pair of poles in response to any deflection of the body with respect to said poles to provide a correcting force on the body including a control source for said control coils comprising at least one power amplifier for each two pairs of poles for supplying a current in said control coils in an amount sufficient to compensate for any upsetting forces acting on the body.