Abstract: A surge control (200) for a compressor (12) which produces a compressed gas in accordance with the invention includes a surge control valve (88) having a variable opening which is controlled by an electrical control signal which controls a flow rate of compressed gas flowing through a bypass line (84) between a point of higher pressure and a point of lower pressure in the compressor to control surge; a pressure transducer (120and 122), coupled to the compressor at a point of pressure higher than an inlet to the compressor, for producing an electrical signal representative of pressure; a filter (124), coupled to the pressure transducer, for filtering a selected frequency component of pressure fluctuations represented in the electrical signal to produce a filtered signal; and a controller (132), coupled to the filter, for producing the control signal as a function of the filtered signal.

Abstract: A refrigeration system which may be operated to control superheat at an inlet to a compressor (12) to produce a controlled superheat or to control a temperature of a fluid cooled by at least one evaporator (68) to provide the cooled fluid at a set temperature by controlling an opening of at least one expansion valve (62) in accordance with the invention includes a temperature control (206) which is activable to control the at least one expansion valve to cool the fluid to a set temperature in response to an enabling signal; a superheat control (208) which is activable to control the at least one expansion valve to control the superheat at the inlet of the compressor in response to an enabling signal; and a controller (204) responsive to the at least one logic operational state of the refrigeration system, for generating one of the enabling signals to activate one of the temperature control or the superheat control to control the at least one expansion valve to control superheat or provide cooled fluid at the

Abstract: A refrigeration system (10) having a compressor rotor (20) rotatably supported by a plurality of hydrodynamic bearings (22 and 24) lubricated by oiless pressurized liquid refrigerant supplied to a refrigerant circuit (36) coupled to the hydrodynamic bearings at least in part from the compressor rotor and pressurizing refrigerant which flows to a condenser (34) providing liquid refrigerant which flows to an evaporator (68) in fluid communication with the condenser includes a bearing pump (26), coupled to the refrigerant circuit and to the condenser, for providing pressurized refrigerant to the refrigerant circuit at a pressure higher than a pressure of the refrigerant provided by the compressor rotor when the bearing pump is operating; and a controller (28) for activating the bearing pump in accordance at least one the predetermined conditions of operation of the refrigeration system.

Abstract: A superheat sensor (10, 100) for sensing the superheat of a fluid (14) flowing through a fluid channel (16) in accordance with the invention includes an aperture (18) within the fluid channel; a sensor body (20) engaging the aperture with a fluid tight seal (26) between the body and the aperture, the sensor body having a sensor body channel (44) in fluid communication with fluid flowing within the fluid channel; a pressure sensor (22) contained within the sensor body having a pressure responsive element in fluid communication with the fluid flowing through the fluid channel for producing an electrical signal representative of pressure of fluid flowing in the fluid channel; a temperature sensor (52) connected to the sensor body having at least one surface in fluid communication with the fluid flowing through the fluid channel for producing an electrical signal representation of temperature of fluid flowing in the fluid channel contacting the at least one surface; and a superheat calculator (56), responsive to

Abstract: A refrigeration system (10) having a compressor rotor (20) rotatably supported by a plurality of hydrodynamic bearings (22 and 24) lubricated by oiless pressurized liquid refrigerant and pressurizing refrigerant which flows to a condenser (34) providing liquid refrigerant which flows to an evaporator (68) in fluid communication with the condenser and the compressor in accordance with the invention includes a refrigeration circuit (36) coupled to the compressor, for providing pressurized refrigerant to the hydrodynamic bearings from the compressor and to the evaporator; a bearing pump (26), coupled to the refrigerant circuit and to the condenser, for providing pressurized refrigerant to the refrigeration circuit; a first temperature sensor (101) sensing a temperature Tsink of a heat exchange fluid at the condenser and providing a temperature signal representative of the temperature Tsink of the heat exchange fluid at the condenser; a second heat exchange sensor (103) sensing a temperature Tsource of a heat exc