A fluid compressor includes a case, a fixed scroll, an orbiting scroll, a motor, and at least one anti-rotation unit. The case is configured to form an external appearance thereof. The fixed scroll is fixed in the case. The orbiting scroll is engaged with the fixed scroll at one side of the fixed scroll, and performs partitioning of a compression chamber. The motor provides the orbiting scroll with drive power. The anti-rotation unit is coupled to a side surface of the orbiting scroll so as to prevent rotation of the orbiting scroll.

Methods and systems for detecting and correcting improper operation of a compressor in a refrigeration system and/or an HVAC system include a component level detection and prevention and a system level detection and prevention. The system level detection and prevention can be a backup or a confirmation of the component level detection and prevention. The component level detection and prevention can detect and prevent improper compressor operation within a predetermined time so that the compressor's operation period in an improper direction can be minimized, thereby minimizing wear and damage to the compressor.

An object of the present invention is to provide a rotary displacement compressor capable of determining whether a check valve has failed, and preventing the life of a compressor body from being reduced when a compression operation stops. In order to achieve the object, a rotary displacement compressor includes a compressor body that compresses a medium by reducing a volume of the medium using rotation; a discharge pipe through which a compressed medium, which is discharged through a discharge port of the compressor body, flows; a check valve that shuts off the compressed medium flowing backward to the compressor body; and a backflow control valve that allows a predetermined rate of the compressed medium to flow backward. The check valve and the backflow control valve are disposed in series via the discharge pipe.

A motor-driven compressor includes a compression unit that includes movable and fixed scrolls and a compression chamber, an electric motor that includes a rotor and drives the compression unit, a motor drive circuit that drives the electric motor, an injection port that draws intermediate pressure refrigerant into the compression chamber, a controller that performs rotation control on the rotor, and a voltage detector that detects a terminal voltage of the electric motor. The compression unit compresses low pressure refrigerant drawn into the compression chamber to discharge high pressure refrigerant. The controller is configured to output a stop instruction to deactivate the rotation control of the rotor, determine a rotation condition of the rotor based on the voltage detected by the voltage detector after outputting the stop instruction, and perform, based on the determination, restart preparation control that includes outputting a lock instruction to electrically stop rotation of the rotor.

A scroll compressor includes a movable scroll having first key grooves, a stationary member having second key grooves, and an Oldham coupling provided between the movable scroll and the stationary member. The Oldham coupling is movable with respect to the stationary member along a first axis direction, and with respect to the movable scroll along a second axis direction. The second axis is orthogonal to the first axis and passes through a center of gravity of the Oldham coupling. The Oldham coupling has an annular body portion, at least two first key portions fitted into the first key grooves, and second key portions fitted into the second key grooves. Key gaps are formed between outer peripheral surfaces of the first key portions and inner peripheral surfaces of the first key grooves. The key gaps have first gaps and second gaps wider than the first gaps.

A motor-driven centrifugal pump for circulating a coolant in a primary circuit of a nuclear reactor comprises a sealed motor unit, a hydraulic part and a shaft which is immersed in the coolant, turned by the sealed motor unit and pumping the coolant by an impeller of the hydraulic part secured to the shaft. The motor unit comprises a dry stator and an immersed rotor, mounted securely on the shaft. The motor-driven pump also comprises an immersed flywheel mounted securely on the shaft between the rotor of the motor unit and the impeller of the hydraulic part, allowing a minimum slowing-down time after the electrical power supply is cut; and an immersed anti-backspin device, configured to mechanically block the rotation of the shaft in a predetermined direction.

An electric compressor includes a compression portion discharging a high pressure refrigerant by compressing a low-pressure drawn refrigerant, an electric motor driving the compression portion with a rotation of a rotor, a motor drive circuit driving the electric motor, an intermediate pressure port through which an intermediate pressure refrigerant is introduced into the compression portion, and a controller performing a rotation control of the rotor. When the controller stops the electric motor in a two-step compression mode in which the intermediate pressure refrigerant is introduced into the compression portion, the controller stops the rotor rotating by performing short-circuit braking on the electric motor and then fixes a rotational position of the rotor at a predetermined rotational position by performing direct current excitation on the electric motor.

A motor-driven compressor includes an electric motor including a rotor, a housing, a compression unit, a drive circuit, and a controller. The controller includes a deceleration controller that performs a deceleration control, which decelerates the rotor, during a first period in response to the rotor being rotating in a direction opposite to the forward direction, and a continuation controller that performs a continuation control, which continues the rotation of the rotor, during a second period that is longer than the first period after the deceleration control is performed. A fluctuation difference of a rotational frequency of the rotor during the continuation control is less than a deceleration rotational frequency difference.

Methods and systems for detecting and correcting improper operation of a compressor in a refrigeration system and/or an HVAC system include a component level detection and prevention and a system level detection and prevention. The system level detection and prevention can be a backup or a confirmation of the component level detection and prevention. The component level detection and prevention can detect and prevent improper compressor operation within a predetermined time so that the compressor's operation period in an improper direction can be minimized, thereby minimizing wear and damage to the compressor.

A motor-driven compressor includes a three-phase motor including a rotor, a housing, a compression unit, a drive circuit, and a controller. The drive circuit includes u-phase upper and lower arm switching elements, v-phase upper and lower arm switching elements, and w-phase upper and lower arm switching elements. The controller performs a deceleration control in response to the rotor being rotating in a direction opposite to the forward direction. The controller controls the drive circuit in a switching control mode that includes a first mode, in which one or more switching elements of the upper and lower arm switching elements of the three phases are activated while the remaining switching elements are deactivated, and a second mode, which differs from the first mode in a combination of the activated and deactivated switching elements.