Compression device and method

A centrifugal compression device for a working gas for a refrigeration machine, comprising:

• a plurality of centrifugal compressors forming several successive and/or parallel compression stages, the plurality of centrifugal compressors comprising first and second centrifugal compressors;
• a plurality of drive motors for the plurality of centrifugal compressors, the plurality of drive motors comprising first and second drive motors;
• and
• a gas circuit comprising:
• a first inlet line for the working gas linked to an inlet of the first centrifugal compressor for conveying the working gas into the first compressor,
• a second line linked to an outlet of the first centrifugal compressor and an inlet of the second centrifugal compressor to convey the working gas from the first centrifugal compressor to the second centrifugal compressor,
• at least one third line, each of which being a cooling line, with one end connected to an outlet of at least one of the plurality of centrifugal compressors and at least one second end connected to an inlet of at least one of the plurality of drive motors for transferring a fraction of working gas from one of the plurality of centrifugal compressors into the first and second drive motors in order to limit heating of the drive motor that receives the fraction of working gas, the at least one third line including a first gas cooling member and two parallel branches supplying, respectively, the first and second drive motors for cooling purposes,
• fourth lines linking an outlet of the first drive motor and an outlet of the second drive motor to the inlet of the first centrifugal compressor to recycle working gas, that was used to limit the heating of the first and second drive motors, to the first centrifugal compressor in order to compress the recycled working gas, and
• at least one second gas cooling member arranged on the fourth lines to remove heat from working gas coming from the first and second drive motors before being returned to the first centrifugal compressor.

A centrifugal compression method for a working gas for a refrigeration machine using a plurality of centrifugal compressors forming several successive and/or parallel compression stages and a plurality of drive motors for the centrifugal compressors, the centrifugal compressors being driven in rotation directly by the drive motors, the plurality of centrifugal compressors comprising first and second centrifugal compressors, the method comprising:

• sequentially compressing a working gas in the first centrifugal compressor then in then in the second centrifugal compressor that are arranged in series;
• drawing off a fraction of working gas leaving at least one of the plurality of centrifugal compressors;
• causing the drawn off working gas to flow through at least one of the plurality of drive motors for cooling purposes;
• cooling the drawn off working gas that has flowed through the at least one of the plurality of drive motors;
• distributing the cooled, drawn off working gas into first and second flows of cooled, drawn off working gas;
• and
• causing the first and second flows of cooled, drawn off working gas to flow in parallel through two separate ones of the plurality of drive motors for cooling purposes.