A refrigeration system is provided with a compressor whose speed is varied to provide load control. In order to prevent compressor damage is lubricating oil pressure sensing control is provided which generates a compressor speed increase signal whenever the oil pressure drops below a predetermined m...http://www.google.de/patents/US5067326?utm_source=gb-gplus-sharePatent US5067326 - Method and apparatus for controlling capacity of a multiple-stage cooling system
