Dynamic mode performance evaluation and energy analysis of mains and inverter driven refrigeration compressors

Abstract

In this study the dynamic mode performance of an inverter driven and direct mains driven compressor has been evaluated using a laboratory-based test facility. The aim was to investigate the influence of the inverter on the start-up performance of a refrigeration system and quantify and compare start-up losses for the two modes of operation. The results indicate that an inverter driven system incurs approximately 5 per cent higher start-up losses than a direct mains driven system. This is mainly due to the ‘soft’ starting capabilities of the inverter (gradual acceleration of the motor). An energy analysis of fixed speed and inverter driven refrigeration systems in air-conditioning applications has shown that despite the additional start-up transient losses of inverter driven systems they lead to higher seasonal efficiencies than fixed-speed systems. This arises from improved steady state performance during low-speed operation at loads below the design load of the system. It has been found that the level of energy savings is a function of the type of compressor employed in the variable-speed system.