Compressor bearing cooling via purge unit

A vapor compression system comprising:

• a compressor comprising:
• a housing assembly (40) having a suction port (24) and a discharge port (26) and a motor compartment (60);
• an electric motor (42) having a stator (62) within the motor compartment and a rotor (64) within the stator, the rotor being mounted for rotation about a rotor axis (500);
• one or more working elements (44) coupled to the rotor to be driven by the rotor in at least a first condition so as to draw refrigerant in through the suction port and discharge said refrigerant out from the discharge port;
• one or more bearings (66, 68) supporting the rotor and/or the one or more working elements;
• and
• one or more bearing feed passages coupled to the bearings to pass fluid along a supply flowpath to the bearings;
• a first heat exchanger (28) coupled to the discharge port to receive refrigerant driven in a downstream direction in the first operational condition of the compressor;
• an expansion device (32) downstream of the first heat exchanger;
• a second heat exchanger (30) downstream of the expansion device and coupled to the suction port to return the refrigerant in the first operating condition;
• and
• a purge unit (400) having:
• a vapor inlet line (410) for receiving a refrigerant flow;
• and
• a return line (414, 417A, 417B) for returning a contaminant-depleted refrigerant flow, wherein:
• the supply flowpath (407A, 407B) extends from the purge unit;
• the supply flowpath comprises a first branch (407A) extending to a first (66) of the bearings and a second branch (407B) extending to a second (68) of the bearings;
• and
• a weir (496) in the purge unit divides flow between the supply flowpath first branch and second branch.

A vapor compression system comprising:

• a compressor comprising:
• a housing assembly (40) having a suction port (24) and a discharge port (26) and a motor compartment (60);
• an electric motor (42) having a stator (62) within the motor compartment and a rotor (64) within the stator, the rotor being mounted for rotation about a rotor axis (500);
• one or more working elements (44) coupled to the rotor to be driven by the rotor in at least a first condition so as to draw refrigerant in through the suction port and discharge said refrigerant out from the discharge port;
• one or more bearings (66, 68) supporting the rotor and/or the one or more working elements;
• and
• one or more bearing feed passages coupled to the bearings to pass fluid along a first supply flowpath (100) to the bearings and a second supply flowpath (407A, 407B) to the bearings;
• a first heat exchanger (28) coupled to the discharge port to receive refrigerant driven in a downstream direction in the first operational condition of the compressor;
• an expansion device (32) downstream of the first heat exchanger;
• a second heat exchanger (30) downstream of the expansion device and coupled to the suction port to return the refrigerant in the first operating condition;
• a purge unit (400) having:
• a vapor inlet line (410) for receiving a refrigerant flow;
• and
• a return line (414, 417A, 417B) for returning a contaminant-depleted refrigerant flow, wherein the second supply flowpath (407A, 407B) extends from the purge unit;
• and
• a controller (200) configured to operate (604) the purge unit to supply (630) refrigerant along the supply flowpath in a start-up condition, wherein the controller is configured to:
• determine (660) an insufficiency of refrigerant flow to the bearings along the first supply flowpath (100);
• and
• responsive to the determined insufficiency, operate (622) the purge unit to supply the refrigerant along the second supply flowpath in a non-start-up condition.