During rotation of a shaft of a downhole-type wellbore system, a first signal corresponding to an axial position of the rotating shaft is transmitted by a sensor. The shaft is axially levitated by a plurality of magnetic thrust bearings. A controller determines an amount of axial force to apply to the rotating shaft to maintain axial levitation of the rotating shaft based on the first signal. The controller transmits a second signal corresponding to the determined amount of axial force to the plurality of magnetic thrust bearings. The plurality of magnetic thrust bearings applies the amount of axial force on the rotating shaft to maintain the axial levitation of the rotating shaft based on the second signal.

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 solid-state circuit protector includes a first power semiconductor device having an ON resistance that increases with increasing temperature and a second power semiconductor device connected in parallel with the first power semiconductor device having an ON resistance that decreases with increasing temperature. During times when abnormally high currents are flowing through the solid-state circuit protector, the second power semiconductor is switched ON so that some or all of the current is diverted through it, thus protecting the first power semiconductor device from being damaged due to overheating. The first power semiconductor device is either switched OFF, allowing it to cool in anticipation of a lighter load, or is configured to remain ON so that it shares the burden of carrying the high current with the parallel-connected second power semiconductor device yet operates cooler and at a lower ON resistance since it is not required to pass the full current.

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 device for grounding an overhead line of a segment of rail track. Accord including a first electrical conductor configured for connecting electrically to the overhead line of the segment of rail track, a second electrical conductor configured for connecting electrically to ground and/or a return line of the segment of rail track, a switch configured to enable and disable a connection between the first and second electrical conductors, control means configured to activate and deactivate the switch, and communication means configured for wireless communication with a remote communication device, for receiving a control signal from the remote communication device and for accordingly actuating the control means for activating and deactivating the switch, or for blocking the switch, wherein the communication means are configured for communication over a public telecommunication network.

An overcurrent protection apparatus that protects, from overcurrent, a load circuit including an electric load and wiring electrically connected with each other is provided. The overcurrent protection apparatus includes: a semiconductor switching element that is configured to control energization to the load circuit; and a breaker that stops the semiconductor switching element upon detection of abnormality of overheat or overcurrent at the semiconductor switching element, the breaker having a latch operation mode of continuously stopping the semiconductor switching element even upon cancellation of abnormality detection, and a retry operation mode of canceling stoppage of the semiconductor switching element upon the cancellation of the abnormality detection. The breaker is configured to initially operate in the latch operation mode upon the abnormality detection, and then be switched to the retry operation mode after satisfaction of a predetermined condition.

Current sensors measure current flowing into and out of an inductive load such as a solenoid coil and provide signals to a processor when the difference between the two measured currents exceeds a threshold. A solenoid coil and electronic devices driving it are protected from damage caused by a short circuit at the connections to the coil.

A solid state switch has at least one FET-type device and at least one thyristor-type device coupled in parallel to the at least one FET-type device. The at least one FET-type device is constructed with a first power loss profile based on a rated current of an electrical device; and the at least one thyristor-type device is constructed with a second power loss profile based on a surge current associated with the electrical device.