Compressor for a refrigerating plant comprising: at least two cylinders ; at least two pistons , which slides alternately inside the cylinders ; at least two heads provided with two suctions chambers , connected to a suction line of the plant and to the cylinders to supply the at least two cylinders with a refrigerating fluid, and with a first suction valve , configured to regulate the refrigerating fluid flow rate to a first cylinder ; the first suction valve being movable between a first position, wherein is defined a first flow area which allows the suction of a first flow rate of refrigerating fluid, and a second position wherein is defined a second flow area smaller than the first flow area which allows the suction of a second flow rate of refrigerating fluid lower than the first flow rate; wherein a first suction chamber is divided into two portions by a partition provided with an opening through which the refrigerating fluid flows; wherein the first suction valve comprises a shutter configured to engage the opening of the first suction chamber in the second position; the shutter and the opening being shaped so as to define the first flow area in the first position and the second flow area in the second position; and wherein there is at least a second cylinder ; at least a second piston , which slides alternately inside the second cylinder ; a second head provided with a second suction chamber , connected to the suction line of the plant and to the second cylinder to supply the second cylinder with a refrigerating fluid, and with a second suction valve , configured to regulate the refrigerating fluid flow rate to the second cylinder ; the second suction valve being movable between a third position, wherein is defined a third flow area which allows the suction of a third flow rate of refrigerating fluid, and a fourth position wherein the third flow area is occluded. at least two cylinders ; at least two pistons , which slides alternately inside the cylinders ; at least two heads provided with two suctions chambers , connected to a suction line of the plant and to the cylinders to supply the at least two cylinders with a refrigerating fluid, and with a first suction valve , configured to regulate the refrigerating fluid flow rate to a first cylinder ; the first suction valve being movable between a first position, wherein is defined a first flow area which allows the suction of a first flow rate of refrigerating fluid, and a second position wherein is defined a second flow area smaller than the first flow area which allows the suction of a second flow rate of refrigerating fluid lower than the first flow rate; wherein a first suction chamber is divided into two portions by a partition provided with an opening through which the refrigerating fluid flows; wherein the first suction valve comprises a shutter configured to engage the opening of the first suction chamber in the second position; the shutter and the opening being shaped so as to define the first flow area in the first position and the second flow area in the second position; and wherein there is at least a second cylinder ; at least a second piston , which slides alternately inside the second cylinder ; a second head provided with a second suction chamber , connected to the suction line of the plant and to the second cylinder to supply the second cylinder with a refrigerating fluid, and with a second suction valve , configured to regulate the refrigerating fluid flow rate to the second cylinder ; the second suction valve being movable between a third position, wherein is defined a third flow area which allows the suction of a third flow rate of refrigerating fluid, and a fourth position wherein the third flow area is occluded. <EOS>