A multi-compressor system having individual oil balancing lines

Abstract

The multi-compressor system ( 7 ) includes a plurality of compressors ( 8 ) which are parallelly coupled; a common suction line ( 14 ) and inlet connection lines ( 15 ) each connecting the common suction line ( 14 ) to a suction fitting ( 11 ) of a respective compressor ( 8 ); a common discharge line ( 16 ) and outlet connection lines ( 17 ) each connecting the common discharge line ( 16 ) to a discharge fitting ( 12 ) of a respective compressor ( 8 ); a plurality of individual oil balancing lines ( 18 ) each fluidly connecting low pressure volumes of two respective compressors ( 8 ) of the plurality compressors, at least one compressor ( 8 ) comprising two oil balancing line connections ( 19 ) formed in the respective compressor shell ( 9 ) and each connected to a respective individual oil balancing line ( 18 ), and two compressors including a single oil balancing line connection ( 19 ) formed in the respective compressor shell ( 9 ) and connected to a respective individual oil balancing line ( 18 ); and a controller configured to operate the multi-compressor system ( 7 ) according to a plurality of predetermined authorized operating configurations.

What is claimed is: 
     
         1 . A multi-compressor system comprising:
 a plurality of compressors which are parallelly coupled, the plurality of compressors comprising at least three compressors, each compressor including a compressor shell provided with a suction fitting and a discharge fitting,   a common suction line and inlet connection lines each connecting the common suction line to the suction fitting of a respective compressor, the inlet connection lines having identical or similar dimensions,   a common discharge line and outlet connection lines each connecting the common discharge line to the discharge fitting of a respective compressor,   a plurality of individual oil balancing lines each fluidly connecting low pressure volumes of two respective compressors of the plurality compressors, at least one compressor of the plurality of compressors comprising two oil balancing line connections formed in the respective compressor shell and each connected to a respective individual oil balancing line, and two of the plurality of compressors comprising a single oil balancing line connection formed in the respective compressor shell and connected to a respective individual oil balancing line, and   a controller configured to control operation of the multi-compressor system, the controller being configured to operate the multi-compressor system according to a plurality of predetermined authorized operating configurations and being configured to prevent operation of the multi-compressor system according to a plurality of predetermined forbidden operating configurations.   
     
     
         2 . The multi-compressor system according to  claim 1 , wherein the plurality of predetermined authorized operating configurations includes part-load operation configurations where only one of the compressors having a single oil balancing line connection is stopped while all the other compressors of the plurality of compressors are running. 
     
     
         3 . The multi-compressor system according to  claim 1 , wherein the plurality of predetermined authorized operating configurations includes part-load operation configurations where the two compressors having a single oil balancing line connection are stopped while all the other compressors of the plurality of compressors are running. 
     
     
         4 . The multi-compressor system according to  claim 1 , wherein the plurality of predetermined authorized operating configurations includes part-load operation configurations where at least two of the plurality of compressors are running and only one of the two compressors having a single oil balancing line connection is stopped, while the compressor, which has two oil balancing line connections and which is adjacent and coupled, via an oil balancing line, to said compressor having a single oil balancing line connection which is stopped, is stopped. 
     
     
         5 . The multi-compressor system according to  claim 1 , wherein the plurality of predetermined forbidden operating configurations includes part-load operation configurations where at least two of the plurality of compressors are running and one of said at least two compressors, which are running, is a compressor comprising a single oil balancing line connection, while the compressor, which has two oil balancing line connections and which is adjacent and coupled, via an oil balancing line, to said compressor comprising a single oil balancing line connection which is running, is stopped. 
     
     
         6 . The multi-compressor system according to  claim 1 , wherein the plurality of predetermined forbidden operating configurations includes part-load operation configurations where one compressor of the at least one compressor comprising two oil balancing line connections is running, while all the others compressors of the plurality of compressors are stopped. 
     
     
         7 . The multi-compressor system according to  claim 1 , wherein the plurality of predetermined authorized operating configurations includes part-load operation configurations where only one of the plurality of compressors is running and said only one compressor which is running is a compressor comprising a single oil balancing line connection. 
     
     
         8 . The multi-compressor system according to  claim 1 , wherein each of the plurality of individual oil balancing lines includes a tubular connecting part including a first end portion connected to an oil balancing line connection formed in the compressor shell of a respective compressor, a second end portion connected to an oil balancing line connection formed in the compressor shell of a respective compressor, and an intermediate portion located between the respective first and second end portions and fluidly connecting said respective first and second end portions. 
     
     
         9 . The multi-compressor system according to  claim 8 , wherein each of the plurality of individual oil balancing lines includes:
 a first oil level regulating part fluidly connected to the first end portion of a respective tubular connecting part and protruding into the compressor shell of the respective compressor, and   a second oil level regulating part fluidly connected to the second end portion of a respective tubular connecting part and protruding into the compressor shell of the respective compressor.   
     
     
         10 . The multi-compressor system according to  claim 1 , wherein each compressor of the plurality of compressors is a scroll compressor. 
     
     
         11 . The multi-compressor system according to  claim 1 , wherein the plurality of compressors comprises at least four compressors, the plurality of compressors comprising at least two compressors each comprising two oil balancing line connections and two compressors each comprising a single oil balancing line connection. 
     
     
         12 . A refrigeration system comprising a refrigerant circulation circuit successively including a condenser, an expansion device, an evaporator and a multi-compressor system according to  claim 1  connected in series. 
     
     
         13 . A method of controlling operation of a multi-compressor system, the method comprising:
 providing a multi-compressor system including:
 a plurality of compressors which are parallelly coupled, the plurality of compressors comprising at least three compressors, each compressor including a compressor shell provided with a suction fitting and a discharge fitting, 
 a common suction line and inlet connection lines each connecting the common suction line to the suction fitting of a respective compressor, the inlet connection lines having identical or similar dimensions, 
 a common discharge line and outlet connection lines each connecting the common discharge line to the discharge fitting of a respective compressor, 
 a plurality of individual oil balancing lines each fluidly connecting low pressure volumes of two respective compressors of the plurality of compressors, at least one compressor of the plurality of compressors comprising two oil balancing line connections formed in the respective compressor shell and each connected to a respective individual oil balancing line, and two of the plurality of compressors comprising a single oil balancing line connection formed in the respective compressor shell and connected to a respective individual oil balancing line, 
   preventing operation of the multi-compressor system according to a plurality of predetermined forbidden operating configurations,   selecting a predetermined authorized operation configuration among a plurality of predetermined authorized operation configurations, and   operating the multi-compressor system according to the selected predetermined authorized operation configuration.