ITRI has successfully developed an oil-free centrifugal compressor using active magnetic bearings. The oil free chiller can improve at least 15％ performance after getting rid of lubrication oil in the refrigeration systems (due to less friction loss and better heat exchange). We have already installed more than 10 compressors on field testing in domestic sites. The key tech. include high efficiency compressing components, AMB and drive, high speed motor and driver, precision machining, etc.