Analyses for sensorless linear compressor using linear pulse motor

A reciprocating compressor with a rotary motor which is used in a refrigerator has low efficiency, since it has large mechanical losses due to the crank mechanism. In a free piston linear compressor with linear motors, the mechanical losses of the crank mechanism can be decreased and system efficiency improved. However, the compressor will fail and the system efficiency will be reduced if the piston position is not controlled successfully. A linear pulse motor (LPM) generally has precise positioning ability in open-loop control without a position sensor. Therefore, the authors expect that a sensorless linear compressor system with an LPM can be realized. In this paper, they examine the piston positioning accuracy and the efficiency of a sensorless linear compressor system with an LPM for various compressor sizes and operating conditions by using analytical and experimental approaches. As a result, the efficiency of the linear compressor system is higher than that of a conventional reciprocating compressor using an induction motor. The system efficiency is significantly improved in the linear compressor with LPM.