Effects of the driving voltage waveform on the performance of vapor compression cycle system driven by the moving coil oil-free linear compressor

Abstract

The effect of driving voltage waveforms on the performance of refrigeration system driven by a moving coil oil-free linear compressor is experimentally investigated in this study. The tested driving voltage waveforms have three types: square, sine without the crest and trough, sine without the trough. The results show that the displacement curves under these three kinds of driving voltage are similar to that of the standard sine curve, but the current curves are completely different. The motor efficiency for each voltage waveform is lower than that of the sine waveform, especially that the motor efficiency of the square waveform is reduced by 40% at 60 Hz. Compared with the sine waveform, the coefficient of performance (COP) of the sine without the trough waveform is increased by 11% at 60 Hz resulted from the decrease of piston offset, while the COPs of the other two waveforms are lower than that of sine waveform due to the decrease of the motor efficiency. In addition, it is found that the sine without the trough waveform, as the only non-symmetric voltage waveform among the three tested waveforms, can effectively reduce the piston offset and obtain the similar performance to the sine waveform with direct component.