Patent ID: 8584487

Claim:
A refrigerant system comprising: a main compressor to compress refrigerant and to circulate the refrigerant throughout said refrigerant system; a secondary compressor, said secondary compressor at least partially driven by an expander, where at least a portion of the refrigerant circulating throughout said refrigerant system is expanded in said expander from a higher pressure to a lower pressure; a control for determining desired characteristics of an expansion process, and said control being operable to control a load on the expander provided by said secondary compressor to achieve said desired characteristic of said expansion process; said control determining whether an increase or a decrease of a speed of the expander is desired, and increasing the load on said secondary compressor if a decrease in the speed of said expander is desired, and decreasing the load on said secondary compressor when an increase in the speed of the expander is desired; and said secondary compressor compresses fluid other than the refrigerant circulating throughout said refrigerant system.