A design method for a six-pole hybrid magnetic bearing with symmetrical suspension forces. A magnetic bearing is designed by taking particularity that a permanent magnet of the six-pole hybrid magnetic bearing with symmetrical suspension forces forms magnetic polarity on a stator suspension tooth as the starting point and taking maximum suspension forces in x and y directions and a saturation magnetic density as constraint conditions. Compared with a method for designing the maximum radial suspension force in a +x direction in a manner that a saturation magnetic induction intensity is reached in the +x direction and the magnetic induction intensity in a −x direction is zero in existing design of a six-pole hybrid magnetic bearing, this method enables the maximum magnetic suspension forces in the +x and +y directions to be same, so that the radial suspension forces of the six-pole hybrid magnetic bearing are designed to be completely symmetrical.

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 control system for controlling a magnetic suspension system includes controllers each being configured to control one or more of magnetic actuators magnetically levitating an object. One of the controllers is configured to operate as a master controller and other one or ones of the controllers are configured to operate as one or more slave controllers. The master controller is communicatively connected with one or more digital data transfer links to the one or more slave controllers and configured to control operation of the one or more slave controllers. The control system makes it possible to implement a centralized control with separate controllers, and thereby without a need for a controller having a high number of controller current sources.

A magnetic bearing assembly for a rotary machine having a rotor shaft, comprising a stator magnetic circuit secured to a stationary support element and comprising at least one body of ferromagnetic material and at least one coil, both being fitted in a protective annular housing leaving uncovered a surface of revolution of said ferromagnetic body and a surface of revolution of said one coil, the magnetic bearing assembly comprising an annular thrust collar secured to the rotor shaft and radially extending towards the stator magnetic circuit by a radial portion, said radial portion facing the uncovered surfaces of said ferromagnetic body and said one coil. The annular thrust collar comprises at least one flow channel.

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.

Disclosed is a displacement correction apparatus. The apparatus comprises: a reference circuit and a correction circuit; the reference circuit is configured to provide a reference signal; the correction circuit is configured to perform a logarithm operation on a nonlinear displacement signal to be corrected based on the reference signal, to obtain a corrected linear displacement signal. The displacement correction apparatus can solve the problem of poor detection accuracy resulting from a position signal output by an eddy current sensor being not in a linear relationship with a displacement signal of a shaft, thereby achieving the effect of improving detection accuracy. A magnetic levitation bearing system and a displacement correction method therefor which use the above displacement correction apparatus are also disclosed.

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.

An electromagnetic rotary drive includes a rotor, a stator and windings. The rotor includes a magnetically effective core. The rotor is contactlessly magnetically drivable about an axis of rotation and the rotor is contactlessly magnetically levitatable. The stator has coil cores, each with a longitudinal limb parallel with the axis and a transverse limb extending radially, the transverse limb being perpendicular to the axis. The windings generate an electromagnetic rotational field, each winding surrounding one longitudinal limb, such that the stator is free of permanent magnets. The rotor is ferromagnetic or ferrimagnetic with one preferential magnetic direction extending radially, and the core of the rotor has a magnetic resistance in the preferential magnetic direction, the magnetic resistance at most half as large as the magnetic resistance in a direction, which is perpendicular to the preferential magnetic direction and perpendicular to the axial direction.

Provided is a circuit that eliminates harmonics generated in a synchronous detection circuit to achieve low vibration and low noise, along with a position detection device, a magnetic bearing device, and a vacuum pump. An odd-order harmonic of a sensor carrier frequency can be eliminated from a displacement signal by setting a duty of a switch of the synchronous detection circuit to a specified value. Conditions for a pulse generation method are adjusted to generate a pulse at a phase angle of 180 degrees + 360 degrees x n. A duty of a pulse for a synchronous detection switch is set such that a positive-side area and a negative-side area of a harmonic waveform are equal to each other. Moreover, the pulse duty is adjusted to center the phase angle at which a sensor signal has a highest sensitivity.

The present disclosure relates to a stiffness enhancing mechanism for a magnetic suspension bearing, a magnetic suspension bearing including the stiffness enhancing mechanism, and a blood pump. The magnetic suspension bearing comprises a stator with stator teeth and a rotor disposed within the stator. The stiffness enhancing mechanism comprises: a rotor permanent magnet, a stator permanent magnet, and an axial driving body. The rotor permanent magnet and the rotor of the magnetic suspension bearing form a rotor assembly, which has an asymmetric structure with respect to the main plane (P) of the rotor. The stiffness enhancing mechanism is configured such that the stator permanent magnet generates a radial attractive force to the rotor permanent magnet, and the axial driving body generates an axial repulsive force to the rotor permanent magnet, wherein the magnitude of the axial repulsive force is variable with a change of an axial distance between the axial driving body and the rotor permanent magnet). The stiffness enhancing mechanism can increase the torsional stiffness of the rotor of the magnetic suspension bearing and facilitate the miniaturization of the magnetic suspension bearing.