An example centrifugal compressor includes a housing that defines an inlet chamber and includes first and second openings that define a recirculation passage in fluid communication with the inlet chamber. An impeller is disposed within the housing and is rotatable about a longitudinal axis to draw fluid into the inlet chamber. The first and second openings are at different axial locations along the longitudinal axis. A plurality of inlet guide vanes are rotatable and situated in the inlet chamber. The centrifugal compressor includes a ring and a controller for moving the ring along the longitudinal axis between a first position and a second position when rotating the inlet guide vanes. The ring obstructs at least one of the first and second openings more in the second position than in the first position.

An electric motor system includes a drive shaft, a first electric motor, a second electric motor, a first inverter, a second inverter and a control unit. The drive shaft is rotatable around an axis. The first electric motor and the second electric motor rotate the drive shaft. The first inverter supplies power in order to generate a torque to the first electric motor. The second inverter supplies power in order to generate a torque to the second electric motor. The control unit controls the first inverter and the second inverter. The controller is configured to be able to change a ratio between an output torque of the first electric motor and an output torque of the second electric motor.

A refrigeration system includes a rotary pressure exchanger fluidly coupled to a low pressure loop and a high pressure loop. The rotary pressure exchanger replaces a traditional bulk flow compressor. The rotary pressure exchanger is configured to receive the refrigerant at high pressure from the high pressure loop, to receive the refrigerant at low pressure from the low pressure loop, and to exchange pressure between the refrigerant at high pressure and the refrigerant at low pressure, and wherein a first exiting stream from the rotary pressure exchanger includes the refrigerant at high pressure in the supercritical state or the subcritical state and a second exiting stream from the rotary pressure exchanger includes the refrigerant at low pressure in the liquid state or the two-phase mixture of liquid and vapor.

A scroll compressor including an orbiting scroll having a small diameter compared to a case in which an oil groove is provided in a ring shape and constantly communicates with an outlet of an oil passage. The scroll compressor includes a fixed scroll and an orbiting scroll configured to orbit in engagement with the fixed scroll. The fixed scroll includes an outlet of an oil passage configured to communicate with an oil tray storing lubricant, the outlet of the oil passage connected to a sliding surface of the orbiting scroll. The orbiting scroll includes a plurality of oil grooves configured not to communicate with each other so as to supply the lubricant to a sliding surface of the fixed scroll, the plurality of oil grooves configured to communicate with the outlet at least once and not to communicate with the outlet at least once while the orbiting scroll rotates once.

A refrigerant compressor includes: a sealed container in which refrigerating machine oil is stored; an electric element accommodated in the sealed container and driven by electric power supplied from outside; and a compression element accommodated in the sealed container and covered with the refrigerating machine oil, the compression element being driven by the electric element to compress refrigerant gas supplied from outside. The refrigerating machine oil contains an oil film shortage adjusting agent in a dissolved state in such a concentration that deposition of the oil film shortage adjusting agent does not occur at least while the refrigerant compressor is operating.

A turbo compressor includes a housing with a refrigerant suction hole, through which a refrigerant is introduced, at a front portion thereof, and a motor case defining an accommodation space. The accommodation space includes a rotation shaft extending in a front-rear direction and a motor that is configured to rotate the rotation shaft. A first impeller is coupled to one end of the rotation shaft and a second impeller is coupled to the other end of the rotation shaft. The first impeller is configured to primarily compress the refrigerant introduced into the refrigerant suction hole. A connection passage, that surrounds the motor case extends backward from an outlet of the first impeller. The second impeller is configured to secondarily compress the refrigerant introduced through the connection passage.

The motor driving apparatus includes a switch that is a mechanical switch for changing coil connection states of a motor; an inverter that generates alternating voltage from direct voltage and outputs the alternating voltage to the motor; and a control device that controls the switch and the inverter. The control device causes the switch to change the coil connection states while the alternating voltage output from the inverter is zero.

A motor includes a cover including a first cup body and a second cup body, each including a bottomed tubular shape. The first cup body and the second cup body are disposed with openings of the peripheral wall portions facing each other. The second cup body includes a bottom wall portion provided with stud bolts projecting from the bottom wall portion to one axial direction and spaced apart from each other in a circumferential direction. An end surface of a heat sink, facing the one axial direction, is in contact with a portion positioned between the stud bolts adjacent to each other in the circumferential direction in a surface of the bottom wall portion of the second cup body in the other axial direction.

An electric motor and a compressor having an electric motor are disclosed herein. The electric motor may include a stator having a stator core and a stator coil, and a rotor provided with a rotational shaft and rotatably disposed with respect to the stator. The stator coil may include a main winding and an auxiliary winding connected to each other with a phase difference. The main winding may be divided into a plurality of main windings so as to be connected to each other and disconnected from each other, and the stator coil may further include a winding changeover switch configured to provide connection and disconnection between the plurality of main windings. Such a configuration may allow operating efficiency at a low load to be increased.

A rotary-machine control device includes: a connection switching device switching a connection state of stator windings of a rotary machine; a current detection unit detecting a rotary machine current flowing in the rotary machine; a voltage application unit applying voltage to the rotary machine; a control unit generating a voltage command provided to the voltage application unit and outputting a switching command to switch the connection state to the connection switching device; and an open-phase determination unit determining presence or absence of disconnection in the rotary machine or presence or absence of disconnection of a power distribution line to the rotary machine. During rotation of the rotary machine, the control unit outputs the switching command and the open-phase determination unit determines presence or absence of disconnection.