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A centrifugal compressor unit includes a driving means for rotatably driving a rotor, and at least one compressor including a statoric body and an arrangement of blade wheels mounted on a shaft which is rotatably driven by the rotor in the statoric body. The group formed by the motor and/or each com

A centrifugal compressor unit includes a driving means for rotatably driving a rotor, and at least one compressor including a statoric body and an arrangement of blade wheels mounted on a shaft which is rotatably driven by the rotor in the statoric body. The group formed by the motor and/or each compressor being mounted in a common housing is sealed from the gas used by the compressor. The compressor unit also includes an arrangement of active bearings for axially and radially guiding the rotor and the driven shaft, and a means for cooling the driving means and the guiding bearings by withdrawing the gas used by the compressor at the outlet of a first compression stage. The cooling means includes a set of internal conduits for supplying the driving means and the bearings with cooling gas. The cooling gas flow in the motor and the cooling gas flow in the bearing is separated and then converge upstream of the first compression stage.

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1. A centrifugal compressor unit comprising: a motor means rotationally driving a rotor; andat least one compressor comprising: a stator body; anda set of impeller wheels which are mounted on a driven shaft rotationally driven by the rotor in the stator body;wherein the motor and the at least one co

1. A centrifugal compressor unit comprising: a motor means rotationally driving a rotor; andat least one compressor comprising: a stator body; anda set of impeller wheels which are mounted on a driven shaft rotationally driven by the rotor in the stator body;wherein the motor and the at least one compressor is mounted in a common housing sealed against the gas handled by the compressor unit;a set of active bearings for axially and radially guiding the rotor and the driven shaft; andcooling means for cooling the motor means and the guide bearings by tapping off some of the gas handled by the compressor at an outlet from a first compression stage, passing the gas through the motor means and through the bearings and reinjecting the gas into an inlet side of one of the at least one compressor, wherein the cooling means are equipped with filtering means for filtering the gas handled by the compressor, wherein the cooling means comprises a set of internal passages for feeding the motor means and the bearings with cooling gas which are formed in the compressor unit, and wherein the flow of cooling gas in the motor means is separate from the flow of cooling gas in the bearings, and wherein the flow of cooling gas converges upstream of the first compression stage. 2. The centrifugal compressor unit of claim 1, wherein the cooling means further comprises a set of external lines collecting the gas on the outlet side of the first compression stage and feeding the internal passages in parallel. 3. The centrifugal compressor unit of claim 2, wherein the internal passages for feeding the motor means are fed in parallel with the internal passages for feeding the bearings with cooling gas. 4. The centrifugal compressor unit of claim 1, wherein, with the driven shaft of the compressor supported by two end radial bearings, the cooling means comprise an axial passage running from one bearing to the other and fed at one of its ends by the external lines, and wherein the axial passage globally running longitudinally and radially externally through the compressor. 5. The centrifugal compressor unit of claim 1, wherein the internal passages for feeding the bearings comprise a set of directional passages directed radially externally in the compressor, and wherein each internal passage feeds one bearing. 6. The centrifugal compressor unit of claim 1, wherein the motor is fed with cooling gas via an orifice formed in an end cover and in communication with an external line. 7. The centrifugal compressor unit of claim 1, wherein the internal passages for feeding the bearings comprise a set of directional passages directed radially externally in the compressor, and wherein each internal passage feeds one bearing, and wherein the motor is fed with cooling gas via an orifice formed in an end cover and in communication with an external line, and wherein the flow of cooling gas is mixed with the flow of cooling gas leaving the bearings cooled by the gas coming from the internal passages. 8. The centrifugal compressor unit of claim 1, further comprising means for regulating a refrigeration flow rate for the motor and for each bearing. 9. The centrifugal compressor unit of claim 1, further comprising means for collecting flows of cooling gas from members situated on a same side as an equalizing piston. 10. The centrifugal compressor unit of claim 2, wherein the external lines are equipped with filtering means for filtering the gas handled by the compressor. 11. The centrifugal compressor unit of claim 10, wherein, with the driven shaft of the compressor supported by two end radial bearings, the cooling means comprise an axial passage running from one bearing to the other and fed at one of its ends by the external lines, and wherein the axial passage globally running longitudinally and radially externally through the compressor. 12. The centrifugal compressor unit of claim 11, wherein the internal passages for feeding the bearings comprise a set of directional passages directed radially externally in the compressor, and wherein each internal passage feeds one bearing. 13. The centrifugal compressor unit of claim 12, wherein the motor is fed with cooling gas via an orifice formed in an end cover and in communication with an external line. 14. The centrifugal compressor unit of claim 13, wherein the flow of cooling gas is mixed with the flow of cooling gas leaving the bearings cooled by the gas coming from the internal passages. 15. The centrifugal compressor unit of claim 10, further comprising means for regulating a refrigeration flow rate for the motor and for each bearing. 16. The centrifugal compressor unit of claim 10, further comprising means for collecting flows of cooling gas from members situated on a same side as an equalizing piston.