Two-stage linear compressor

A control system for managing operation of a dual-piston linear compressor with an economizer cycle wherein a first piston operates as a first stage of the economizer cycle and a second piston operates as a second stage of the economizer cycle, the control system comprising:

• a controller coupled to the linear compressor to control a volume flow ratio of the linear compressor and to vary the linear compressor between the economizer cycle having a first gas flow path through the linear compressor and a single stage cycle having a second gas flow path through the linear compressor, the first gas flow path partially defined by the first piston receiving gas from an evaporator line and discharging gas to an economizer line, and further partially defined by the second piston receiving gas from the economizer line and discharging gas to a condenser line such that a suction chamber of the second stage is in fluid communication with a discharge chamber of the first stage;
• a first sensor coupled to the controller to measure a first operating condition including a suction pressure of the linear compressor;
• a second sensor coupled to the controller to measure a second operating condition including a discharge pressure of the linear compressor;
• and
• wherein the controller measures piston stroke of the first piston and piston stroke of the second piston, and
• further wherein based upon the first operating condition measured by the first sensor, the second operating condition measured by the second sensor, and the piston stroke of at least one of the first and second pistons, the controller varies operation of at least one of the first and second pistons until the volume flow ratio is at a point of maximum efficiency.

A refrigeration system comprising:

• a two-stage linear compressor including a first piston disposed in a first cylinder and a second piston disposed in a second cylinder, the linear compressor operable in an economizer cycle wherein the first piston operates as a first stage of the economizer cycle and the second piston operates as a second stage of the economizer cycle;
• a controller coupled to the linear compressor to control a volume flow ratio in the linear compressor and to vary the linear compressor between the economizer cycle having a first gas flow path through the linear compressor and a single stage cycle having a second gas flow path through the linear compressor, the first gas flow path partially defined by the first piston receiving gas from an evaporator line and discharging gas to an economizer line, and further partially defined by the second piston receiving gas from the economizer line and discharging gas to a condenser line such that a suction chamber of the second stage is in fluid communication with a discharge chamber of the first stage,
• wherein the controller stores a plurality of coefficients of performance for a range of particular operating conditions of the linear compressor, each coefficient of performance corresponding to a desired volume flow ratio and a desired secondary evaporating temperature, and
• further wherein based upon measured operating conditions of the linear compressor the controller determines a highest coefficient of performance from the plurality of coefficients of performance and varies operation of at least one of the first and second pistons to achieve either the desired volume flow ratio or the desired secondary evaporating temperature.