Cycle gas refrigerator and liquefaction facility

A cycle gas refrigerator comprising:

• a cycle circuit containing a cycle gas comprising at least one of the following:
• nitrogen, helium, and hydrogen, the cycle circuit being configured to subject the cycle fluid to a thermodynamic cycle that brings the cycle fluid to a given cryogenic temperature at least at one end of the cycle circuit, the cycle circuit comprising:
• a compression mechanism configured to compress the cycle fluid;
• a cooling mechanism configured to cool the cycle fluid;
• and
• an expansion mechanism configured to expand the cycle fluid, wherein the expansion mechanism of the cycle fluid comprises at least two turbines rotatably mounted on respective rotary shafts, the compression mechanism comprising at least three rotary compressors arranged in parallel in the cycle circuit and mounted respectively on three rotary shafts, at least two of the rotary shafts being respectively coupled to one of the two turbines, respectively, so as to recover work of expansion of the cycle fluid for compressing the cycle fluid,
• at least one motor configured to drive at least one of the rotary shafts bearing a turbine and a compressor and in that at least the two parallel-connected compressors coupled to a turbine are each associated with a respective flow measuring member configured to measure a flow rate passing through the respective compressor and with a respective regulating member configured to regulate the flow rate admitted to the compressor,
• wherein the at least two turbines coupled to the compressors each comprise a respective sensor configured to measure a rotational speed of the turbine and a respective controlling system configured to control the rotational speed of the respective turbine, an electronic control and command member which comprises a microprocessor and is configured to receive measurements from the measurement members configured to measure the flow rate and from the sensors configured to measure the speed and to command the regulating members configured to regulate the flow rate, and
• wherein the parallel-connected compressors are identical,
• wherein the electronic control and command member is configured to apply a set value for the flow rate admitted to the compressors which is identical for all of the parallel-connected compressors.