A semi-integrated sensorless PM brushless drive for a 42 V automotive HVAC compressor

The automotive industry is working hard to add new features that enhance passenger comfort and safety, improve vehicle fuel economy and reduce environmental emissions. The 42 V Power Net for future automobiles allows one to add such features in an efficient manner. This paper describes a semi-integrated PM brushless drive for a 42 V electric compressor for automotive HVAC. Electric compressors have advantages of low refrigerant emissions, flexible packaging, and efficient variable speed operation. These are intended for vehicles where the engine shuts-off during stops as in "stop and go" (starter-generator) or for vehicles with auxiliary power units (fuel cells). A low cost semi-integrated position sensorless motor controller has been designed, built and tested over wide speed range with overall system efficiencies of 85% or more over a significant portion of its operating range. Issues related to sensorless operation, packaging and thermal management, EMI abatement and performance of the drive are discussed.