Analysis of the mechanical operating characteristics and resonance performance of linear compressors under variable frequency conditions

Abstract

This study investigates the electrical operating characteristics and resonance performance of a moving-magnet linear compressor under variable-frequency conditions. A three-phase permanent-magnet linear motor simulation model was established based on vector-control principles. An experimental test bench was then built to evaluate the compressor under different stroke, frequency, and load conditions. Under no-load conditions, motor efficiency decreased with increasing frequency at a fixed stroke and also decreased with increasing stroke at a fixed frequency. The motor force constant was ∼83 N/A within the main operating range. Under loaded conditions, both current and input power first decreased and then increased with frequency, while motor efficiency showed the opposite trend, reaching its maximum near the resonance frequency. At resonance, current and velocity were nearly in phase. In addition, a three-dimensional force-current-stroke map was constructed from the experimental data, and the effect of capacitive compensation on system performance was analysed. The results provide experimental support for high-efficiency zone design and control optimisation of linear compressors.