The instability of a linear compressor is studied by an experiment on a developed linear compressor in a refrigerator. The experimental results show that there are three types of unstable phenomena: the start-up process

external disturbance process

and solenoid valve adjustment process. During the start-up process

an unstable status is caused by the adjustment of the supply power and changes in the refrigerant suction/discharge pressure. This finally settles down as the supply power and suction/discharge pressure are unchanged. Some external disturbance of the refrigeration system causes an unstable oscillation with a fluctuation of about 0.3 mm of the piston displacement. Accordingly

the current and the input power fluctuate at about 10% of their average values. This oscillation gradually becomes stable as there is no more disturbances. The solenoid valve adjustment process has a great influence on the stability of a linear compressor. In this experiment

the maximal fluctuation amplitude of the displacement is about 2.2 mm

and the piston is apt to strike the cylinder. Therefore

the design optimization for a linear compressor structure

and a control strategy based on the change characteristics of the working conditions

is necessary to ensure operational reliability and high efficiency.