Abstract: A sensor device for determining an axial position of a body (10) along a longitudinal axis (A) comprises an excitation coil (23) that extends around the longitudinal axis, one or more first detection coils (21) arranged in the vicinity of the excitation coil in a first detection plane (P1), and one or more second detection coils (22) arranged in the vicinity of the excitation coil in a second detection plane (P2). Excitation circuitry supplies the excitation coil (23) with current at an excitation frequency to create an excitation magnetic field distribution. Detection circuitry determines the axial position of the body based on signals from the first and second detection coils at the excitation frequency. The detection circuitry bases the determination of the axial position on at least one difference between the signals from the first detection coils and the signals from the second detection coils.

Abstract: A magnetic bearing device comprises a stator (30) and a rotor (10) supported in the stator for rotation around a rotation axis (R). The rotor comprises at least one permanent magnet (21, 22) that is magnetized along the rotation axis. The stator comprises at least one closed magnetic core (31) that surrounds the rotor (10) and at least one radial bearing winding (32) arranged on the closed magnetic core (31) in a toroidal configuration. The at least one radial bearing winding is arranged to interact with a permanent magnetic field generated by the at least one permanent magnet to obtain a radial bearing force when current is supplied to the at least one radial bearing winding.

Abstract: A magnetic bearing device for magnetically suspending a rotor (22) for rotation about a rotation axis (A) comprises an amplifier device, a first main coil (p) and a second main coil (n). In order to compensate for a stray flux that is created when the main coils are supplied with currents from the amplifier device, a compensation coil (c) is connected between a common node of the main coils and the amplifier device with such polarity that a current flowing through the compensation coil will diminish the stray flux caused by the main coils (p, n).

Abstract: A contactless electromagnetic sensor (1) for determining a radial position of a rotor comprises a transducer (100) that comprises one or more coils. Excitation circuitry is connected to the transducer to energize the transducer. Processing circuitry derives at least one position signal indicative of a radial position of the rotor based on the transducer signals. In order to enable simplified compensation for disturbance signals resulting from target imperfections, the coils have a sensitivity to a target material that varies sinusoidally along the circumferential direction.

Abstract: A magnetic bearing device for magnetically suspending a rotor (22) for rotation about a rotation axis (A) comprises an amplifier device, a first main coil (p) and a second main coil (n). In order to compensate for a stray flux that is created when the main coils are supplied with currents from the amplifier device, a compensation coil (c) is connected between a common node of the main coils and the amplifier device with such polarity that a current flowing through the compensation coil will diminish the stray flux caused by the main coils (p, n).

Abstract: A contactless electromagnetic sensor device for determining displacements of a rotor (120) is disclosed. Two sensing coils (612, 614) interact with surfaces of the rotor. A bridge circuit is formed by the sensing coils and by two secondary windings (212, 213) of an input transformer (210). The primary winding of the input transformer receives an excitation signal. An output signal is obtained at an output tap formed by a common node between the sensing coils (612, 614) and a common node between the secondary windings of the input transformer. In this manner excitation and detection are separated. If cables are used for connecting the bridge circuit to signal processing circuitry, the input and output impedances of the bridge circuit can be matched to the characteristic impedance of the cables. An output transformer can be connected to the output tap. The roles of the input and output transformers can be interchanged.

Abstract: A contactless electromagnetic sensor device for determining displacements of a rotor (120) is disclosed. Two sensing coils (612, 614) interact with surfaces of the rotor. A bridge circuit is formed by the sensing coils and by two secondary windings (212, 213) of an input transformer (210). The primary winding of the input transformer receives an excitation signal. An output signal is obtained at an output tap formed by a common node between the sensing coils (612, 614) and a common node between the secondary windings of the input transformer. In this manner excitation and detection are separated. If cables are used for connecting the bridge circuit to signal processing circuitry, the input and output impedances of the bridge circuit can be matched to the characteristic impedance of the cables. An output transformer can be connected to the output tap. The roles of the input and output transformers can be interchanged.

Abstract: A magnetic bearing device and a method of operation for such a device are provided. The device comprises a group (410) of electromagnetic actuators (411, 412, 413, 414). Each actuator is electrically connected to an amplifier unit (701). The actuators of a first subgroup are connected to a first common node (608), while the actuators of a second subgroup are connected to a second common node (609). The common nodes (608, 609) are connected either directly or through means like an additional actuator. Preferably the common nodes (608, 609) have no additional electrical connection to the amplifier unit. According to a special embodiment of the invention, each subgroup of actuators consists of only one single actuator and the common node has an electrical connection to the amplifier. Thus the device comprises two actuators in a series configuration connected to an H bridge. The common node may be connected to either of two different voltages.

Abstract: A magnetic bearing device (1) with an improved vacuum-tight electrical feedthrough through its housing (10) is disclosed. The feedthrough (30) comprises a flat connection element (31) such as a rigid or flexible printed circuit board extending through the wall of the housing (10), preferably all the way along an inner circumference of the housing. The connection element is sealed in a gas-tight manner to the housing. The element preferably has a central opening (36) for receiving the rotor shaft. Connections to the bearing units and sensors may be achieved by flat-ribbon cables (51) or flexprints. The sensors are preferably also implemented as printed sensors. Thus a very compact and cost-efficient magnetic bearing device can be obtained. An alternative embodiment uses a connection element on a side wall of the housing as a feedthrough to the bearing components.

Abstract: A rotor shaft (200) for a magnetic bearing device (1) is disclosed. The shaft comprises an inner portion on whose periphery a plurality of targets (240, 260, 280) separated by spacers (250, 270) are mounted. This is achieved exerting an axial pressing force (F, F?) to the peripheral parts, rather than applying a radial press fit. In this manner, a simplified construction, a higher stiffness and a higher stability at high rotational speed are achieved. Further disclosed is a rotor having a thrust disk (220) whose diameter decreases towards the periphery. This allows to use a larger thrust disk at a given rotational speed.

Abstract: A magnetic bearing device (1) for rotatably supporting a shaft (20) for rotation about a rotation axis (101) is disclosed. The device (1) comprises a first active radial bearing (5), one or more first radial displacement sensors (81), and an axial bearing (6, 7). At least a part of the axial bearing (6, 7) is disposed between the first active radial bearing (5) and the first radial displacement sensors (81) when viewed in an orthogonal projection onto the rotation axis (101). A vacuum pump including the magnetic bearing device (1) and a multiple-sensing unit (8) are also disclosed.

Abstract: A lunar phase display mechanism includes an upper disc which is the lunar display disc and a lower disc mounted concentrically to this disc. One of the discs is mounted so that during normal operation of the mechanism that one disc rotates relative to the other disc, and the other disc is mounted in a stationary position during normal operation of the mechanism while this position can be changed by a rotary motion. The gear train driving the rotating disc allows that the direction of rotation of this disc can be reversed so that the different appearance of the lunar phases at the latitudes of the earth and, in particular, in the northern and southern hemisphere can be taken into account in the display.

Abstract: A method and a controller for controlling a magnetic bearing device, in which a rotor is suspended for rotation around a shaft, are disclosed. Sensor signals are transformed to yield tilt displacement signals (S?x, S?y) which correspond to tilting displacements of the shaft in predetermined directions (x, y). From the tilt displacement signals (S?x, S?y), tilt control signals A?x, A?y) are derived; these are transformed to yield actuator control signals for driving electromagnetic actuators in the magnetic bearing device. According to the invention, tilting displacements for which the tilt vector rotates about the device axis (z) with a first predetermined sense of rotation are controlled separately from tilting displacements for which the tilt direction vector rotates about the device axis (z) with a second sense of rotation opposite to the first predetermined sense of rotation. In this way, control of nutation and precession can be achieved without influence from blade vibrations or shaft bending modes.

Abstract: A magnetic hearing device and a method of operation for such a device are provided. The device comprises a group (410) of electromagnetic actuators (411, 412, 413, 414). Each actuator is electrically connected to an amplifier unit (701). The actuators of a first subgroup are connected to a first common node (608), while the actuators of a second subgroup are connected to a second common node (609). The common nodes (608, 609) are connected either directly or through means like an additional actuator. Preferably the common nodes (608, 609) have no additional electrical connection to the amplifier unit. According to a special embodiment of the invention, each subgroup of actuators consists of only one single actuator and the common node has an electrical connection to the amplifier. Thus the device comprises two actuators in a series configuration connected to an H bridge. The common node may be connected to either of two different voltages.

Abstract: A magnetic bearing device (1) with an improved vacuum-tight electrical feedthrough through its housing (10) is disclosed. The feedthrough (30) comprises a flat connection element (31) such as a rigid or flexible printed circuit board extending through the wall of the housing (10), preferably all the way along an inner circumference of the housing. The connection element is sealed in a gas-tight manner to the housing. The element preferably has a central opening (36) for receiving the rotor shaft. Connections to the bearing units and sensors may be achieved by flat-ribbon cables (51) or flexprints. The sensors are preferably also implemented as printed sensors. Thus a very compact and cost-efficient magnetic bearing device can be obtained. An alternative embodiment uses a connection element on a side wall of the housing as a feedthrough to the bearing components.

Abstract: A rotor shaft (200) for a magnetic bearing device (1) is disclosed. The shaft comprises an inner portion on whose periphery a plurality of targets (240, 260, 280) separated by spacers (250, 270) are mounted. This is achieved exerting an axial pressing force (F, F?) to the peripheral parts, rather than applying a radial press fit. In this manner, a simplified construction, a higher stiffness and a higher stability at high rotational speed are achieved. Further disclosed is a rotor having a thrust disk (220) whose diameter decreases towards the periphery. This allows to use a larger thrust disk at a given rotational speed.

Abstract: A device for contact-less measurement of distances (10, 20) in multiple directions of an electrically conductive body (2, 22) comprises a plurality of inductive elements (1, 4, 7). At least one (1) of the plurality of inductive elements (1, 4, 7) is placed essentially around the body (2). The other inductive ele-ments or other magnetic field sensors (4, 7) are provided in the vicinity of said one inductive element (1). The device with these features allows integrating a multi axis inductive sensor on a single circuit board.

Abstract: A method and a controller for controlling a magnetic bearing device, in which a rotor is suspended for rotation around a shaft, are disclosed. Sensor signals are transformed to yield tilt displacement signals (S?x, S?y) which correspond to tilting displacements of the shaft in predetermined directions (x, y). From the tilt displacement signals (S?x, S?y), tilt control signals A?x, A?y) are derived; these are transformed to yield actuator control signals for driving electromagnetic actuators in the magnetic bearing device. According to the invention, tilting displacements for which the tilt vector rotates about the device axis (z) with a first predetermined sense of rotation are controlled separately from tilting displacements for which the tilt direction vector rotates about the device axis (z) with a second sense of rotation opposite to the first predetermined sense of rotation. In this way, control of nutation and precession can be achieved without influence from blade vibrations or shaft bending modes.

Abstract: A magnetic bearing device (1) for rotatably supporting a shaft (20) for rotation about a rotation axis (101) is disclosed. The device (1) comprises a first active radial bearing (5), one or more first radial displacement sensors (81), and an axial bearing (6, 7). At least a part of the axial bearing (6, 7) is disposed between the first active radial bearing (5) and the first radial displacement sensors (81) when viewed in an orthogonal projection onto the rotation axis (101). A vacuum pump including the magnetic bearing device (1) and a multiple-sensing unit (8) are also disclosed.