A magnetic bearing (20) comprises: a rotor (22) to be supported for rotation about an axis (502); a stator (24) extending from a first end (30) to a second end (32) and comprising: one or more first permanent magnets (50); one or more second permanent magnets (52) of polarity substantially opposite to a polarity of the one or more first permanent magnets; and laminate teeth, encircled by radial windings (36A, 36B), axially between and extending radially inward of the one or more first permanent magnets on one side and the one or more second permanent magnets on the other side. The rotor comprises: one or more third permanent magnets (150); and one or more fourth permanent magnets (152) axially spaced from the one or more third permanent magnets.

A magnetic bearing (20) comprises: a rotor (22) to be supported for rotation about an axis (502); a stator (24) extending from a first end (30) to a second end (32) and comprising: one or more first permanent magnets (50); one or more second permanent magnets (52) of polarity substantially opposite to a polarity of the one or more first permanent magnets; and laminate teeth, encircled by radial windings (36A, 36B), axially between and extending radially inward of the one or more first permanent magnets on one side and the one or more second permanent magnets on the other side. The rotor comprises: one or more third permanent magnets (150); and one or more fourth permanent magnets (152) axially spaced from the one or more third permanent magnets.

A rotating machine includes a housing, a rotor shaft to rotate about a longitudinal axis, a position sensor to detect a position of the rotor shaft within the housing, and a magnetic bearing assembly coupled to the housing to support the rotor shaft within the housing. The magnetic bearing assembly includes an active magnetic bearing for active support of the rotor shaft, such as a thrust bearing actuator to produce an axial force component that is parallel to the central longitudinal axis and a radial force component that is orthogonal to the central longitudinal axis and axially offset from the thrust bearing actuator. The magnetic bearing assembly also includes a passive magnetic radial bearing to radially support the rotor shaft within the housing. A controller electrically coupled to the active magnetic bearing controls a control current to the active magnetic bearing.

The present invention relates to a motor driving device which can reduce a load burden on a rotating shaft when a magnetic bearing is initially operated. When a rotor and a stator are initially aligned, the motor driving device can apply a greater current to a coil positioned farthest away from the ground among a plurality of coils than to the other coils, so as to reduce a levitation force necessary for initial alignment of the rotor and the stator.

A magnetic bearing control apparatus and a vacuum pump which do not require a displacement sensor, which enable control with high accuracy, and which are small and low cost. A rate of change (di/dt) that is a time derivative of a current value I.sub.m flowing through an electromagnet varies in accordance with a magnitude of a displacement of a gap between a target member and the electromagnet. The rate of change (di/dt) can be obtained by detecting a voltage value V.sub.s that is generated at both ends of an inductive element. Therefore, by detecting the voltage value V.sub.s, the magnitude of the displacement of the gap can be estimated by calculation. Inductive elements are connected in series to electromagnets and the voltage V.sub.s between the inductive elements is detected by the differential input amplifier. A single period of switching of a PWM switching amplifier is constituted by a current control period of the electromagnet and a displacement detection period for detecting the rate of change (di/dt). In addition, the displacement detection period is further constituted by a current increase period and a current decrease period which are certain periods of time. The current increase period and the current decrease period are equal to each other.

A thrust magnetic bearing device includes: a thrust disc fixed to a rotating body; and a pair of electromagnets provided so as to sandwich the thrust disc and be spaced apart from the thrust disc in a direction along a rotation axis. Each of the pair of electromagnets includes: a coil wound around the rotation axis of the rotating body; and a ring-shaped core accommodating the coil. The core includes a slit which is located at at least one circumferential position of the core and extends from an outside outer peripheral surface as a starting point toward a center of the core. The slit is formed in a range including at least an inside outer peripheral surface.

A rolling bearing device includes a bearing portion and a power generation portion. The power generation portion has a plurality of projecting portions provided on an outer ring spacer, a pair of core members provided on an inner ring spacer, a magnet, and a coil. The power generation portion generates an induced current in the coil as the projecting portions pass in the vicinity of first side end portions of the core members during rotation. There are two different loop paths along which magnetism generated by the magnet flows: a first loop path formed when the projecting portions are close to the first side end portions of the core members; and a second loop path formed when the projecting portions and the first side end portions of the core members are away from each other.

A magnetic bearing (20) comprises: a rotor (22) to be supported for rotation about an axis (502); a stator (24) extending from a first end (30) to a second end (32) and comprising: one or more first permanent magnets (110); one or more second permanent magnets (112) of polarity substantially opposite to a polarity of the one or more first permanent magnets; at least three radial windings (40,42,44,46); a first axial winding (34); a second axial winding (36); a first end pole (120); and a second end pole (122).

A magnetic bearing device comprises a radial magnetic bearing configured to magnetically levitate and support a rotor shaft in a radial direction; an axial magnetic bearing configured to magnetically levitate and support, in an axial direction, a rotor disc rotatable together with the rotor shaft; and an axial displacement sensor disposed on a surface of an electromagnet core of the axial magnetic bearing facing the rotor disc and configured to detect axial displacement of the rotor disc.

A device (24) for controlling a magnetic bearing (22) includes an axis with two electromagnets (26, 28) diametrically opposed. The device (24) includes two power converters per axis of the magnetic bearing. Each power converter supplies one different electromagnet. The device includes eight power devices (40, 42, 44, 46, 48, 50, 52, 54) arranged in a first line (88) and a second line (90). Each of the first and second lines includes four power devices. A first set of four power devices (40, 42, 44, 46) are connected together to form a first power converter. A second set of four power devices (48, 50, 52, 54) are connected together to form a second power converter. Each of the first and second lines (88, 90) includes two power devices (40, 42, 44, 46) of the first set and two power devices (48, 50, 52, 54) of the second set.