A measurement tool includes a rotor to rotate about a longitudinal axis, an axial gap generator having a stator assembly adjacent to the rotor, and a movable support structure to which the stator assembly is mounted. The axial gap generator generates a voltage signal as a function of a gap spacing between the stator assembly and the rotor, where the gap spacing is parallel to the longitudinal axis. The movable support structure moves the stator assembly parallel to the longitudinal axis based at least in part on a physical property of an environment about the movable support structure.

An electric stator surrounds a rotor and is configured to cause the rotor to rotate or generate electricity in the electric stator when the rotor rotates. The electric stator is spaced from the rotor and defines a first annular fluid gap in-between that is in fluid communication with an outside environment exterior the electric machine. A radial bearing includes a first portion coupled to the rotor and a second portion coupled to the electric stator. The first portion is spaced from the second portion defining a second annular fluid gap in-between that is in fluid communication with the outside environment exterior the electric machine.

A rotor is surrounded by a stator. A radial bearing includes a first radial bearing portion coupled to the rotor and a second radial bearing portion coupled to the stator. A thrust-bearing includes a first portion coupled to the rotor. The first portion is spaced from a second portion coupled to the stator defining a first annular fluid gap in-between that is in fluid communication with an outside environment exterior the downhole-type machine. The thrust bearing is configured to support an axial load of the rotor within the stator.

A system comprising a turbomachinery provided with a casing and having a rotor mounted on a shaft supported for rotation in the casing; the shaft is associated to a plurality of active magnetic bearings adapted to support the shaft in the casing and associated to a control system through a plurality of wires wherein the control system is housed in a control system compartment external to the casing and located in proximity thereto.

A system to provide power to a tool includes an electric motor that can operate at rotary speeds of at least 6,000 rpm, a variable speed drive electrically connected to the electric motor, and a step-up transformer electrically coupled to the electric motor and the variable speed drive, in which the variable speed drive can generate and transmit a drive signal to supply power to the electric motor when the electric motor is spaced apart from the variable speed drive by a distance of at least 100 meters, and the transformer can prevent capacitive leakage in the drive signal transmitted over the distance from the variable speed drive to the electric motor.

A magnetic bearing supports an object to be supported in a noncontact manner by means of a composite electromagnetic force of first and second electromagnets. A processor-based controller causes a first current and a second current to be controlled according to the following equations,

[00001]$\begin{array}{cc}{i}_1=\frac{g_0-\mathrm{ax}}{g_0}.Math.\left(i_b+i_d\right)& \left(1\right)\\ i_2=\frac{g_0+\mathrm{ax}}{g_0}.Math.\left(i_b-i_d\right)& \left(2\right)\end{array}$

where i.sub.1 is the first current flowing to the first electromagnet, i.sub.2 is the second current flowing to the second electromagnet, i.sub.d is a control current, i.sub.b is a bias current, g.sub.0 is a reference gap length, x is a displacement amount of the object to be supported with respect to a center position, and a is a predetermined correction coefficient.

An electric machine includes a stator having a phase arrangement, and a rotor. The phase arrangement includes legs connected in parallel at first and second primary junctions. Each leg includes a plurality of coils connected in series through a respective intermediate junction. Each leg is connected to at least one other leg by a branch at the respective intermediate junctions such that the phase arrangement is a bridge circuit. The phase arrangement conducts a motor current through the respective coils between the first and second primary junctions. The phase arrangement permits an alignment current to flow between the first and second primary junctions along an alignment current path which passes through at least one coil of two different legs via a respective branch. The motor currents cause a torque to be applied to the rotor, and the alignment current causes a translational force to be applied to the rotor.

An electric machine includes a stator having a phase arrangement, and a rotor. The phase arrangement includes first and second legs connected in parallel at first and second primary junctions. The legs each include first and second coils connected in series through a first intermediate junction. The intermediate junctions are connected by a branch such that the phase arrangement is a bridge circuit. The phase arrangement permits an alignment current to flow between the primary junctions via the branch, the alignment current being conducted through an alignment current path passing through one coil of each leg. The phase arrangement includes a negative impedance converter to add a negative electrical impedance to the alignment current path by introducing additional electrical energy into the respective alignment current path. The alignment current causes a translational force to be applied to the rotor for maintaining alignment of the rotor with respect to the stator.

There is provided a controller for magnetic levitation equipment comprising a plurality of current source modules for connecting to at least one power supply for direct current, DC, and said current source modules comprising current channels for actuating coils of the magnetic levitation equipment, and a controller device connected to the current source modules by a control connection for controlling switching of electric current by the current source modules to the current channels. The current source modules combine discrete components for amplifying and switching electric current to the current channels into a single package. In this way, manufacturing and maintenance of the controller is facilitated, since manufacturing and maintenance may be based on the current source modules instead of discrete components, e.g. gate drivers, IGBTs, power mosfets and diodes.

A control apparatus includes a constant storage portion that stores constant values of an electromagnet coil including a resistance value Rm, an inductance Lm, a sampling time Ts, etc. A current storage portion stores previous current command values Ir having been regularly sampled by a microcomputer inside a current control circuit. A low-frequency feedback circuit generates a signal for suppressing an error between DC components and low-frequency components of an input current command value Ir and a detected current value IL and outputs the signal. An output voltage computing circuit calculates, based on the input current command value Ir[n+1], a stored value Ir[n] of the current storage portion, a stored value of a constant storage portion, and the signal of the low-frequency feedback circuit, a voltage for suppling the electromagnet coil with a current in accordance with a command, and outputs the calculated voltage.