Consistent with the current industrial market demands for increased capacity of small compressors, Mitsubishi Heavy Industries, Ltd. (MHI) has developed the smallest and most lightweight DC twin rotary compressor for R410A refrigerant with a maximum capacity of 6 HP. The company approached this design challenge by defining various capacity increase limitations utilizing its original technologies and then successfully reducing the crankshaft deflection under heavy-load operating conditions. At the same time, MHI has succeeded in producing a highly reliable and efficient compressor, which is the smallest and most lightweight unit in the industry, by maintaining the oil circulation ratio during operation and increasing the refrigerant circulation volume to levels comparable with those found in conventional-sized compressors.