Chicago Pneumatic CPVSd29 Silent Variable Speed Screw Air Compressor with Tank & Dryer | 22kW 30HP 500L. The Chicago Pneumatic Variable Speed compressor series CPVSd allows you to drastically reduce your operating costs when your equipment is not working at full capacity all day long. The integrated inverter reduces the motor speed to match your air consumption and as a result, you save energy and money. The CPVSd is great as a stand-alone machine or networked to a load-unload CP compressor where it can function as a master and regulate the air delivery for the whole site. The smart, high efficient solution for your industrial needs. The CPVSd is our high efficiency screw compressor range which set a new milestone in compressed air.