Compressor/expander machine

A method for operating a refrigerant circuit, having a cooling device or a heat pump or a vapor compression system, with a first heat exchanger in which expanded refrigerant absorbs heat, and with a compressor/expander machine for compressing the expanded refrigerant, a second heat exchanger in which compressed refrigerant emits heat, and including an expansion unit for expanding the compressed refrigerant, wherein the compressor/expander machine has a machine housing with a screw rotor housing, in which at least one screw rotor is arranged between a low-pressure side and a high-pressure side for compressing/expanding the working medium, the screw rotor being coupled to a motor/generator unit, the method comprising:

• for operating the compressor/expander machine, providing an operation control unit which, in the event of termination of operation of the compressor/expander machine, controls the speed of the motor/generator unit in accordance with a predetermined speed curve until a lowest speed range of the at least one of screw rotor is reached, which prevents damage in the region of the at least one screw rotor.

A method for operating a thermodynamic cycle, wherein an ORC system or a vapor expansion system, comprising a compressor for compressing a working medium, a first heat exchanger for heating the working medium, a compressor/expander machine for expanding the compressed and heated working medium and a second heat exchanger for cooling the expanded working medium, wherein the compressor/expander machine has a machine housing with a screw rotor housing, in which at least one screw rotor arranged between a low-pressure side and a high-pressure side is arranged for compressing/expanding the working medium and is coupled to a motor/generator unit, the method comprising:

• Providing an operation control unit which, in the event of termination of operation of the compressor/expander machine, controls the speed of the motor/generator unit in accordance with a predetermined speed curve until a lowest speed range of the at least one of screw rotor is reached, which prevents damage in the region of the at least one screw rotor.