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  Multi-stage compression system including variable speed motorsUSPTO Application #: 20070065300Title: Multi-stage compression system including variable speed motors Abstract: A multi-stage fluid compression system includes a first centrifugal compressor stage having a first inlet and a first outlet and a second centrifugal compressor stage having a second inlet and a second outlet. The second inlet receives a flow of compressed fluid from the first outlet. A first variable-speed motor is coupled to the first centrifugal compressor stage and is operable to drive the first centrifugal compressor stage at a first speed. A second variable speed motor is coupled to the second centrifugal compressor stage and is operable to drive the second centrifugal compressor stage at a second speed. The first speed and the second speed are each independently variable. (end of abstract) Agent: Michael Best & Friedrich, LLP - Milwaukee, WI, US Inventors: Filippo Maria Mariani, Jay L. Robb USPTO Applicaton #: 20070065300 - Class: 417243000 (USPTO) Related Patent Categories: Pumps, With Intercooler The Patent Description & Claims data below is from USPTO Patent Application 20070065300. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. sec. 119 to provisional patent application No. 60/718,389, filed on Sep. 19, 2005, which is hereby fully incorporated by reference. BACKGROUND [0002] The invention relates to a centrifugal compressor system including two or more compression stages. More particularly, the invention relates to a centrifugal compressor system that includes multiple compression stages independently driven by a directly connected high-speed, variable speed electric motor preferably equipped with active magnetic bearings. [0003] Multiple stage compressor units have been used to provide a higher pressure than would be possible with a single compressor unit. These units are generally driven by a single drive so that all motors operate at a uniform speed or speed ratio. [0004] The use of a single drive motor makes it difficult to vary the operation of one stage with respect to the other stages. For example, a first stage may be operated at an optimal speed under certain conditions. However, this speed may be less than optimal for the other stages. If the stages are driven by a common drive member, the speed of one cannot be varied without changing the speed of the other. SUMMARY [0005] In one embodiment, the invention provides a multi-stage fluid compression system that includes a first centrifugal compressor stage having a first inlet and a first outlet and a second centrifugal compressor stage having a second inlet and a second outlet. The second inlet receives a flow of compressed fluid from the first outlet. A first variable-speed motor is coupled to the first centrifugal compressor stage and is operable to drive the first centrifugal compressor stage at a first speed. A second variable speed motor is coupled to the second centrifugal compressor stage and is operable to drive the second centrifugal compressor stage at a second speed. The first speed and the second speed are each independently variable. [0006] In another embodiment, the invention provides a multi-stage compression system that includes a plurality of centrifugal compressor units. Each compressor unit has an inlet and an outlet. A first of the compressor units draws in a fluid at a first pressure, and a last of the compressor units discharges the fluid at a second pressure. The compression system also includes a plurality of variable-speed motors. Each motor directly drives one of the plurality of compressor units. Each motor is operable at a speed between a motor minimum and a motor maximum independent of the other motors. A control system is operable to vary the speed of each motor independently at least partially in response to the second pressure. [0007] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0008] FIG. 1 shows the cross-section of a compression module. [0009] FIG. 2 is a cross-sectional view of a compressor inlet of the compression module of FIG. 1. [0010] FIG. 3 shows a perspective view of the compression module in a horizontal configuration. [0011] FIG. 4 is a perspective view of the compression module in a vertical configuration. [0012] FIG. 5 is an illustration of the connections and flow from one stage of compressor and heat exchanger to another. [0013] FIG. 6 is a schematic of an embodiment of the compression system. [0014] FIG. 7 is a schematic of two motors, one motor driving one compressor and the other motor driving two compressors. DETAILED DESCRIPTION [0015] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings. [0016] FIG. 1 illustrates a fluid compression module 10 (sometimes referred to as a compression stage or a compression unit) that includes a prime mover, such as a motor 15 coupled to a compressor 20 and operable to produce a compressed fluid. In the illustrated construction, an electric motor 15 is employed as the prime mover. However, other constructions may employ other prime movers such as but not limited to internal combustion engines, diesel engines, combustion turbines, etc. [0017] The electric motor 15 includes a rotor 25 and a stator 30 that defines a stator bore 35. The rotor 25 is supported for rotation on a shaft 40 and is positioned substantially within the stator bore 35. The illustrated rotor 25 includes permanent magnets 45 that interact with a magnetic field produced by the stator 30 to produce rotation of the rotor 25 and the shaft 40. In a preferred construction, the rotor is operable at a speed in excess of 50,000 RPM, with faster and slower speeds also being possible. The magnetic field of the stator 30 can be varied to vary the speed of rotation of the shaft 40. Of course, other constructions may employ other types of electric motors (e.g., synchronous, induction, brushed DC motors, etc.) if desired. [0018] The motor 15 is positioned within a housing 50 which provides both support and protection for the motor 15. A bearing 55 is positioned on either end of the housing 50 and is directly or indirectly supported by the housing 50. The bearings 55 in turn support the shaft 40 for rotation. In the illustrated construction, magnetic bearings 55 are employed with other bearings (e.g., roller, ball, needle, etc.) also suitable for use. In the construction illustrated in FIG. 1, secondary bearings 60 are employed to provide shaft support in the event one or both of the magnetic bearings 55 fail. [0019] In some constructions, an outer jacket 65 surrounds a portion of the housing 50 and defines cooling paths 70 therebetween. A liquid (e.g., glycol, refrigerant, etc.) or gas (e.g., air, carbon dioxide, etc.) coolant flows through the cooling paths 70 to cool the motor 15 during operation. Continue reading... Full patent description for Multi-stage compression system including variable speed motors Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Multi-stage compression system including variable speed motors patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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