Accurate control and indication ofthe capacity YORK Refrigeration has developed three new ammoniaRotatune screw compressors as a supplement to the exist- ing range ofrenowned YORK screw compressors.The Rotatune concept is based on the use ofa frequencyconverter and high-speed motors.This provides a number ofdistinct advantages.The new compressors have been developed on the basis ofthe existing SAB screw compres- sor programme and they will be delivered as complete fac- tory-mounted units.The variable compressor speed ie the capacity ֖ is controlled by the well-known Unisab control system. > Increased COP compared with normal 3000/3600 rpm compressors. > Very high COP even at part load > A low starting current and high power factor avoid heavy demands on the electrical system > Low average noise level > Fewer movable parts result in increased reliability and reduced maintenance costs > Full economizer effect at part load. >