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.

In a vacuum pump, a portion of a lower end portion of a rotating cylindrical body is cut in an axial direction thereof to form an imbalance correction portion (removal portion). Preferably, the removal portion is formed so as to minimize an axial width of the rotating cylindrical body and set a circumferential width of the rotating cylindrical body to a value of not less than a thickness (width in a radial direction) of the rotating cylindrical body. Additionally, a corner formed in the removal portion is formed to have a large. With this configuration, in the rotating cylindrical body, the removal portion is formed to have a shape in which a removal width (depth) in the axial direction of the rotating cylindrical body is small and a removal width in the circumferential direction thereof is large.

A vacuum pump, and a waterproof structure and a control apparatus applied to the vacuum pump which improve efficiency of on-site maintenance work and prevent water from penetrating into a connector connecting portion when a cover is removed during circuit separation or the like. When performing maintenance work, after a chassis of a control apparatus is lowered by around several tens of millimeters, the chassis of the control apparatus is pulled out in a radial direction of a pump. Accordingly, a pump main body and the control apparatus can be readily attached and detached even when sufficient empty space is not available in an axial direction of the vacuum pump. A wall portion is circumferentially protrusively provided in side portions of the base portion and the control apparatus. Furthermore, a sealing member and a lid are inserted into a gap. Therefore, water droplets cannot easily penetrate into the gap.

A vacuum pump and method of mounting a shaft within a vacuum pump is disclosed. The vacuum pump comprises a rotor and a stator. The rotor comprises a shaft comprising pumping elements extending therefrom. The shaft is mounted to rotate and is supported by a plurality of bearings, the plurality of bearings comprising: an axial magnetic bearing and two radial bearings, at least one of the two radial bearings comprising a gas foil bearing.

A vacuum pump comprises: a rotor rotatable in a predetermined rotation direction; and a case housing the rotor; and a fixed component arranged facing an inner wall of the case. A clearance is formed between the inner wall of the case and the fixed component, and a groove allowing communication between the clearance and an exhaust path in the case is formed at either the inner wall of the case or the fixed component.

A pressure difference of liquid is generated between an upper end and a lower end of a thread groove by the action of a thread groove pump formed between the thread groove and a lower end wall portion of a rotating rotor shaft. As a result, liquid of a bottom space is sucked up and passes through a hollow hole and is discharged to the outside of the rotor shaft through communication holes. The discharged liquid passes through the inside of a hub of a rotating body and reaches an extension member where it is sprayed radially in the form of droplets from a protrusion. The droplets are received by a partition wall. Due to the presence of a protrusion in an upper portion of the partition wall, the droplets cannot cross over the partition wall. The accumulated liquid drops through a communication hole to the bottom space.

A vacuum pump includes: a casing formed with an inlet port or outlet port; a stator disposed inside the casing; and a rotor enclosed in the casing and including a shaft rotatably supported on the stator, and a rotor blade formed in a cylindrical shape with a plurality of blades arranged in multiple stages on an outer circumferential portion thereof, and secured to the shaft such as to be integrally rotatable therewith. The rotor blade is provided with a rupture location control groove as a rupture location control means that locally reduces rigidity of the rotor blade to control a location where the rotor blade ruptures.

A vacuum pump, vacuum pump arrangement and method are disclosed. The vacuum pump includes at least one rotor; and a stator, an inlet for receiving gas during operation; and an exhaust for exhausting the gas. The vacuum pump includes a shaft extending through a centre of said pump and comprising a plate mounted on an end of the shaft towards the inlet. The vacuum pump includes control circuitry configured to control an axial position of the plate, a change in axial position of the plate providing a change in inlet conductance of gas to the vacuum pump. The plate is mounted such that it extends beyond the inlet in at least some axial positions of the rotor such that the plate is not on the same side of the inlet as the stator.

The present disclosure can provide a vacuum pump capable of obtaining a rotation direction and correcting the rotation direction without adding a dedicated rotation direction sensor even in a state of low-speed rotation. The control device is capable of obtaining at least a first state in which a rotor shaft rotates at relatively high speed, and a second state in which the rotor shaft deviates within a gap between the rotor shaft and a protective bearing and rotates at relatively low speed while revolving, acquires output information of a radial displacement sensor, obtains a rotation direction of the rotor shaft in the second state on the basis of the output information, determines whether the rotation direction is normal or not, and when the rotation direction is not normal, stops the rotation and increases rotation speed to achieve a normal rotation direction.

An electric submersible pump (ESP) assembly. The ESP assembly comprises an electric motor, a centrifugal pump, and a hybrid magnetic radial bearing, wherein the hybrid magnetic radial bearing is disposed inside the electric motor or disposed inside the centrifugal pump.