| abstract |
A vapor compression system (20) has: a centrifugal compressor (22) having an inlet (40) and an outlet (42); and an electric motor (28) having a stator (30) and a rotor (32). A plurality of bearings (36) support the rotor. A refrigerant charge comprises a base refrigerant and one or more oils. The one or more oils are present at a total concentration of 80-5000 parts per million (ppm) by weight. |