Abstract: A compressor with a rotary driven centrifugal impeller which receives inlet air from an inlet passageway and this discharges compressed air through a radially extending diffuser passageway. Moveable vanes are provided both in the inlet passageway and diffuser passageway for varying the pressure and flow output from the compressor while maintaining the rotary speed of the centrifugal impeller substantially constant. In the preferred form of the invention, the centrifugal impeller and an electrical generator are rotatably driven at a constant speed and in synchronism with each other and, together, form an electrical and pneumatic power system.