A centrifugal compressor for a refrigeration system is disclosed. The centrifugal compressor includes an electric motor, which includes a rotor and a stator. The compressor further includes a housing enclosing the electric motor, a stator cooling passage provided within the housing, and a rotor cooling passageway provided within the housing. The rotor cooling passageway is independent of the stator cooling passageway.

A compressor (20) comprises: a case (22); and at least one piston (40) mounted for reciprocating movement, each in a respective cylinder (42) of the case. The at least one piston has a peripheral surface (50) and an upper surface (52). At least one discharge valve comprises: a valve element (150) shiftable between a closed condition and an open condition; a valve guide (170); one or more springs (180) held at least partially the valve guide biasing the valve element from the open condition toward the closed condition; and one or more vents (300) in the valve guide providing a flow path from a region above the valve element upward through the valve guide.

An apparatus and method for cooling a compressor motor (152) having a motor stator (162) and cooling a rotor (166) in a refrigerant system (100). The method cools the rotor and the stator, electromagnetic bearings (160) located within a compressor housing by providing refrigerant liquid to the stator internal channels, the channels being in fluid communication with a rotor passageway (172), and a flow-control device (168) controlling refrigerant flow into the stator. A temperature monitoring device (176) in communication with a controller (140) monitors motor temperature. The controller (140) evaluates the motor temperature and adjusts refrigerant flow through the flow control device (168), maintaining the motor (152) within a predetermined temperature range.

Methods and related systems for controlling an indoor air temperature for a heat pump system are disclosed. The method includes (a) determining an outdoor coil temperature of an outdoor heat exchanger and a speed of a compressor of a heat pump system, (b) determining a target indoor coil temperature of the indoor coil based on the outdoor coil temperature and the speed of the compressor, and (c) adjusting a speed of air flowing across the indoor coil based on a difference between a current indoor coil temperature and the target indoor coil temperature to reduce the difference between the current indoor coil temperature and the target indoor coil temperature.

A method and apparatus for controlling temperature of a compressor motor (170) having a motor cooling circuit in a refrigeration system (1014) is provided. The motor cooling circuit includes a second expansion valve (1043) providing fluid communication between the condenser and the compressor motor. The compressor motor (170) is in fluid communication with the refrigeration circuit (1014) between downstream of the first expansion valve (1040) and a compressor inlet. Refrigerant is provided as a cooling fluid to the motor cooling circuit. A primary PID loop (402) and a secondary PID loop (414) are used to control the temperature and the flow of refrigerant to the motor (170).

Methods and related systems for controlling an indoor air temperature for a heat pump system are disclosed. In an embodiment, the method includes (a) determining an outdoor coil temperature of an outdoor heat exchanger and a speed of a compressor of a heat pump system. In addition, the method includes (b) determining a target indoor coil temperature of the indoor coil based on the outdoor coil temperature and the speed of the compressor. Further, the method includes (c) adjusting a speed of air flowing across the indoor coil based on a difference between a current indoor coil temperature and the target indoor coil temperature to reduce the difference between the current indoor coil temperature and the target indoor coil temperature.