Homopolar permanent-magnet-biased action magnetic bearing with an integrated rotational speed sensor
First Claim
1. An electromagnetic actuator with an integrated rotational speed sensor for radial support of a rotor having a rotational axis, the electromagnetic actuator comprising:
- a first and a second radial control poles adjacent to an outer surface of the rotor, separated from the outer surface of the rotor by first and second radial control air gaps, respectively, and configured to communicate magnetic flux with the outer surface of the rotor, the first radial control pole and the second radial control pole magnetically coupled to each other, and the first radial control pole, the second radial control pole and the rotor forming a radial control magnetic circuit;
a first and a second electrical windings wound around the first and the second radial control poles respectively and producing radial control magnetic flux in the radial control magnetic circuit when energized with electrical currents;
a bias magnetic flux return pole spaced axially from the radial control poles, adjacent to the outer surface of the rotor, separated from the outer surface of the rotor by an air gap and configured to communicate magnetic flux with the outer surface of the rotor, and the rotor, the first radial control pole, the second radial control pole and the bias magnetic flux return pole forming a magnetic bias circuit;
a permanent magnet magnetically coupled to the first radial control pole, the second radial control pole and the bias magnetic flux return pole and configured to generate magnetic bias flux in the magnetic bias circuit;
the radial control magnetic flux and the magnetic bias flux exert a radial force on the rotor when superimposed in the first and the second radial control air gaps;
a Hall effect sensor configured to measure a magnetic field in the air gap between the magnetic flux return pole and the rotor; and
a speed sensor triggering notch on the outer surface of the rotor that produces a circumferentially local discontinuity in the magnetic field measured by the Hall effect sensor.
1 Assignment
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Accused Products
Abstract
Radial poles are placed around a radial actuator target mounted on a body. The poles are separated from a cylindrical surface of the target by radial gaps and adapted to communicate a magnetic flux with it. The radial poles are equipped with electrical control windings and magnetically coupled to form magnetic control circuits. A flux return pole is adjacent to the body, separated from it by an air gap and adapted to communicate a magnetic flux with the radial actuator target. A permanent magnet generates a magnetic bias flux in the magnetic bias circuit formed by the radial actuator target, the radial poles and the magnetic flux return pole. A radial force is exerted on the actuator when the control windings are energized with a current. A Hall effect sensor measures bias magnetic field in the air gap between the magnetic flux return pole and the body. A feature on a body is adapted to produce a circumferentially local discontinuity in the magnetic field measured by the Hall effect sensor as the body rotates.
97 Citations
17 Claims
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1. An electromagnetic actuator with an integrated rotational speed sensor for radial support of a rotor having a rotational axis, the electromagnetic actuator comprising:
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a first and a second radial control poles adjacent to an outer surface of the rotor, separated from the outer surface of the rotor by first and second radial control air gaps, respectively, and configured to communicate magnetic flux with the outer surface of the rotor, the first radial control pole and the second radial control pole magnetically coupled to each other, and the first radial control pole, the second radial control pole and the rotor forming a radial control magnetic circuit; a first and a second electrical windings wound around the first and the second radial control poles respectively and producing radial control magnetic flux in the radial control magnetic circuit when energized with electrical currents; a bias magnetic flux return pole spaced axially from the radial control poles, adjacent to the outer surface of the rotor, separated from the outer surface of the rotor by an air gap and configured to communicate magnetic flux with the outer surface of the rotor, and the rotor, the first radial control pole, the second radial control pole and the bias magnetic flux return pole forming a magnetic bias circuit; a permanent magnet magnetically coupled to the first radial control pole, the second radial control pole and the bias magnetic flux return pole and configured to generate magnetic bias flux in the magnetic bias circuit; the radial control magnetic flux and the magnetic bias flux exert a radial force on the rotor when superimposed in the first and the second radial control air gaps; a Hall effect sensor configured to measure a magnetic field in the air gap between the magnetic flux return pole and the rotor; and a speed sensor triggering notch on the outer surface of the rotor that produces a circumferentially local discontinuity in the magnetic field measured by the Hall effect sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of generating a radial force to radially support a rotor while measuring the rotational speed of the rotor, the method comprising:
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generating a bias magnetic flux within a bias magnetic circuit comprising the rotor, a radial control pole adjacent to a cylindrical surface of the rotor and separated from the cylindrical surface by an air gap, and a bias magnetic flux return pole adjacent to the rotor and separated from the rotor by an air gap; generating a control magnetic flux, superimposed on top of the bias magnetic flux in the radial control pole to produce a desired radial force; with a notch on the rotor cylindrical surface, causing a circumferentially local discontinuity in the magnetic flux density in the air gap between the rotor and the bias magnetic flux return pole; measuring the magnetic field density changes in the air gap between the rotor and the bias magnetic flux return pole as the rotor rotates with a Hall effect sensor; and counting number of peaks or dips of a signal output from the Hall effect sensor per unit time to calculate the rotational speed of the rotor. - View Dependent Claims (12, 13)
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14. An electric machine system comprising:
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a stator; a rotor having a rotational axis and configured to move relative to the stator; an electromagnetic actuator with an integrated rotational speed sensor subassembly comprising; a plurality of radial poles residing apart from the rotor adjacent a cylindrical outer surface of the rotor and configured to communicate magnetic flux with the cylindrical outer surface of the rotor, the rotor and the plurality of radial poles defining a plurality of radial magnetic control circuits; a bias magnetic flux return pole residing apart from the rotor adjacent the cylindrical outer surface of the rotor and configured to communicate magnetic flux with the rotor; the plurality of radial poles configured to communicate magnetic flux with the rotor and the magnetic bias flux return pole; the rotor, the plurality of radial poles and the bias magnetic flux return pole defining a magnetic bias circuit; radial control conductive coils wound around the radial poles and configured to produce magnetic flux in the radial magnetic control circuit; a Hall effect sensor configured to measure a magnetic field in an air gap between the bias magnetic flux return pole and the rotor; and a notch on the rotor that produces a circumferentially local discontinuity in the magnetic field measured by the Hall effect sensor; a position sensor configured to sense a position of the rotor; a control electronics package configured to control the magnetic fluxes in the radial magnetic control circuits; and an electronics package configured to count peaks or dips in an output signal from the Hall effect sensor per unit time and calculate the rotational speed of the rotor based on this count. - View Dependent Claims (15, 16, 17)
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Specification