Cost Effective Oil free Centrifugal Air Compressor For Textile Industry The air-suspended centrifugal compressor is a Single phase screw air compressor that does not require a gearbox, speed increaser, or coupling. It is directly driven by a high-speed permanent magnet synchronous motor (PMSM), and the motor is controlled by a variable frequency drive(VFD) for speed regulation. The impeller of the compressor is directly coupled to the motor, and the shaft is sus pended on an active air bearing.