A scroll-type machine is disclosed which is particularly well suited for use as a compressor in refrigeration and air conditioning systems and incorporates a unique arrangement for modulating the capacity thereof. The capacity of the scroll-type machine is modulated by reducing the orbital radius of one of the scroll members to thereby form a leakage path across the flank surfaces of the wraps. Both types of scroll separation may be accomplished in a time pulsed manner to thereby enable a full range of modulation with the duration of the loading and unloading periods being selected to maximize the efficiency of the overall system. A motor control arrangement is also disclosed which may be used with either of the modulation methods mentioned above to increase the efficiency of the motor during periods of reduced load. Additionally, either of the modulation arrangements mentioned above may be combined with a delayed suction form of capacity modulation with or without the motor control feature to thereby achieve better operating efficiency under certain conditions.

A control for a refrigeration system serviced by a special pulse width modulated compressor (30) coupled to a condenser (32)and evaporator (42). The system can be of the distributed type wherein the condenser (32) and compressor. (30) may be coupled to service a group of adjacent refrigeration cases, wherein each case would have its own evaporator (42). A controller (52) is coupled to a load sensor (58) for producing a variable duty cycle control signal (54) in which the duty cycle is a function of demand for cooling. Moreover, fuzzy logic technique may be utilized in order to provide self adaptive tuning control for the system.

A control for a refrigeration system serviced by a special pulse width modulated compressor (30) coupled to a condenser (32)and evaporator (42). The system can be of the distributed type wherein the condenser (32) and compressor (30) may be coupled to service a group of adjacent refrigeration cases, wherein each case would have its own evaporator (42). A controller (52) is coupled to a load sensor (58) for producing a variable duty cycle control signal (54) in which the duty cycle is a function of demand for cooling. Moreover, fuzzy logic technique may be utilized in order to provide self adaptive tuning control for the system.

A scroll-type machine is disclosed which is particularly well suited for use as a compressor in refrigeration and air conditioning systems and incorporates a unique arrangement for modulating the capacity thereof. In one group of embodiments the capacity of the scroll-type machine is modulated by relative axial movement between the scroll members so as to form a leakage path across the wrap tips and opposed end plates. In another group of embodiments, modulation is achieved by reducing the orbital radius of one of the scroll members to thereby form a leakage path across the flank surfaces of the wraps. Both types of scroll separation may be accomplished in a time pulsed manner to thereby enable a full range of modulation with the duration of the loading and unloading periods being selected to maximize the efficiency of the overall system. A motor control arrangement is also disclosed which may be used with either of the modulation methods mentioned above to increase the efficiency of the motor during periods of reduced load. Additionally, either of the modulation arrangements mentioned above may be combined with a delayed suction form of capacity modulation with or without the motor control feature to thereby achieve better operating efficiency under certain conditions.

A scroll-type machine is disclosed which is particularly well suited for use as a compressor in refrigeration and air conditioning systems and incorporates a unique arrangement for modulating the capacity thereof. The capacity of the scroll-type machine is modulated by reducing the orbital radius of one of the scroll members to thereby form a leakage path across the flank surfaces of the wraps. Both types of scroll separation may be accomplished in a time pulsed manner to thereby enable a full range of modulation with the duration of the loading and unloading periods being selected to maximize the efficiency of the overall system. A motor control arrangement is also disclosed which may be used with either of the modulation methods mentioned above to increase the efficiency of the motor during periods of reduced load. Additionally, either of the modulation arrangements mentioned above may be combined with a delayed suction form of capacity modulation with or without the motor control feature to thereby achieve better operating efficiency under certain conditions.

A scroll-type machine is disclosed which is particularly well suited for use as a compressor in refrigeration and air conditioning systems and incorporates a unique arrangement for modulating the capacity thereof. The capacity of the scroll-type machine is modulated by reducing the orbital radius of one of the scroll members to thereby form a leakage path across the flank surfaces of the wraps. Both types of scroll separation may be accomplished in a time pulsed manner to thereby enable a full range of modulation with the duration of the loading and unloading periods being selected to maximize the efficiency of the overall system. A motor control arrangement is also disclosed which may be used with either of the modulation methods mentioned above to increase the efficiency of the motor during periods of reduced load. Additionally, either of the modulation arrangements mentioned above may be combined with a delayed suction form of capacity modulation with or without the motor control feature to thereby achieve better operating efficiency under certain conditions.

A scroll-type machine is disclosed which is particularly well suited for use as a compressor in refrigeration and air conditioning systems and incorporates a unique arrangement for modulating the capacity thereof. The capacity of the scroll-type machine is modulated by reducing the orbital radius of one of the scroll members to thereby form a leakage path across the flank surfaces of the wraps. Both types of scroll separation may be accomplished in a time pulsed manner to thereby enable a full range of modulation with the duration of the loading and unloading periods being selected to maximize the efficiency of the overall system. A motor control arrangement is also disclosed which may be used with either of the modulation methods mentioned above to increase the efficiency of the motor during periods of reduced load. Additionally, either of the modulation arrangements mentioned above may be combined with a delayed suction form of capacity modulation with or without the motor control feature to thereby achieve better operating efficiency under certain conditions.

A control for a refrigeration system serviced by a special pulse width modulated compressor (30) coupled to a condenser (32)and evaporator (42). The system can be of the distributed type wherein the condenser (32) and compressor (30) may be coupled to service a group of adjacent refrigeration cases, wherein each case would have its own evaporator (42). A controller (52) is coupled to a load sensor (58) for producing a variable duty cycle control signal (54) in which the duty cycle is a function of demand for cooling. Moreover, fuzzy logic technique may be utilized in order to provide self adaptive tuning control for the system.

A control for a refrigeration system serviced by a special pulse width modulated compressor (30) coupled to a condenser (32)and evaporator (42). The system can be of the distributed type wherein the condenser (32) and compressor (30) may be coupled to service a group of adjacent refrigeration cases, wherein each case would have its own evaporator (42). A controller (52) is coupled to a load sensor (58) for producing a variable duty cycle control signal (54) in which the duty cycle is a function of demand for cooling. Moreover, fuzzy logic technique may be utilized in order to provide self adaptive tuning control for the system.

A scroll-type machine is disclosed which is particularly well suited for use as a compressor in refrigeration and air conditioning systems and incorporates a unique arrangement for modulating the capacity thereof. In one group of embodiments the capacity of the scroll-type machine is modulated by relative axial movement between the scroll members so as to form a leakage path across the wrap tips and opposed end plates. In another group of embodiments, modulation is achieved by reducing the orbital radius of one of the scroll members to thereby form a leakage path across the flank surfaces of the wraps. Both types of scroll separation may be accomplished in a time pulsed manner to thereby enable a full range of modulation with the duration of the loading and unloading periods being selected to maximize the efficiency of the overall system. A motor control arrangement is also disclosed which may be used with either of the modulation methods mentioned above to increase the efficiency of the motor during periods of reduced load. Additionally, either of the modulation arrangements mentioned above may be combined with a delayed suction form of capacity modulation with or without the motor control feature to thereby achieve better operating efficiency under certain conditions.

Provided is an operation control method for a BOG multistage displacement compressor including connected multiple displacement compression units (9,10) for compressing boil off gas (BOG) generated from liquefied natural gas, including: under a predetermined state, performing operation control so that the ratio (load ratio) of a load of a low-pressure stage compression unit (9) to a load of a high-pressure stage compression unit (10) in the BOG multistage displacement compressor is larger than load ratios under states other than the predetermined state. Namely, the BOG multistage displacement compressor is configured so that suction temperature in the low-pressure stage compression unit (9) can be detected, and the predetermined state is set to a state where the detected temperature of the suction temperature is equal to or higher than a set temperature that is preset. According to such a method, even if the low-pressure stage side suction gas has a temperature higher than that in steady operation, the load (gas load) due to a differential pressure between suction gas and discharge gas on the high-pressure stage side can be prevented from exceeding an allowable gas load.

Provided is an operation control method for a BOG multistage displacement compressor including connected multiple displacement compression units (9,10) for compressing boil off gas (BOG) generated from liquefied natural gas, including: under a predetermined state, performing operation control so that the ratio (load ratio) of a load of a low-pressure stage compression unit (9) to a load of a high-pressure stage compression unit (10) in the BOG multistage displacement compressor is larger than load ratios under states other than the predetermined state. Namely, the BOG multistage displacement compressor is configured so that suction temperature in the low-pressure stage compression unit (9) can be detected, and the predetermined state is set to a state where the detected temperature of the suction temperature is equal to or higher than a set temperature that is preset. According to such a method, even if the low-pressure stage side suction gas has a temperature higher than that in steady operation, the load (gas load) due to a differential pressure between suction gas and discharge gas on the high-pressure stage side can be prevented from exceeding an allowable gas load.

A control for a refrigeration system serviced by a special pulse width modulated compressor (30) coupled to a condenser (32)and evaporator (42). The system can be of the distributed type wherein the condenser (32) and compressor. (30) may be coupled to service a group of adjacent refrigeration cases, wherein each case would have its own evaporator (42). A controller (52) is coupled to a load sensor (58) for producing a variable duty cycle control signal (54) in which the duty cycle is a function of demand for cooling. Moreover, fuzzy logic technique may be utilized in order to provide self adaptive tuning control for the system.

A control for a refrigeration system serviced by a special pulse width modulated compressor (30) coupled to a condenser (32)and evaporator (42). The system can be of the distributed type wherein the condenser (32) and compressor (30) may be coupled to service a group of adjacent refrigeration cases, wherein each case would have its own evaporator (42). A controller (52) is coupled to a load sensor (58) for producing a variable duty cycle control signal (54) in which the duty cycle is a function of demand for cooling. Moreover, fuzzy logic technique may be utilized in order to provide self adaptive tuning control for the system.