Among turbo chillers loaded with alternative refrigerant (HFC134a), the AART Series is one of the world's most efficient. This paper discusses the technology used in the New AART Series, a lineup of Turbo Chillers upgraded through the introduction of a two-stage inlet guide vane control mechanism and a vane-less diffuser to enhance performance during partial loads. A high-end, high-speed control panel and inverter-driven motor are combined with a variable-speed control logic. The design takes advantage of the aerodynamic characteristic of the compressor and brings about optimal operational control under changing loads and outside temperatures throughout the year. Compared to the conventional variable-speed machines of the NART-I Series, the new AART Series is expected to save considerably more energy in year-round operation.