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 This article describes this new compressor technology and its first use in an ARI-certified chiller design.THE ingersollrand25cfm175psi11hpaircompressormodel2475f11gka BEARINGSTraditional centrifugal compressors use roller bearings and hydrodynamic bearings, both of which consume power and require oil and ingersollrand25cfm175psi11hpaircompressormodel2475f11gka a lubrication system. Recently, ceramic roller bearings, which avoid issues related to oil and reduce ingersollrand25cfm175psi11hpaircompressormodel2475f11gka power consumption, were introduced to the HVAC industry. The lubrication of these bearings is provided by the refrigerant itself. (1)Magnetic-bearing technology is significantly ingersollrand25cfm175psi11hpaircompressormodel2475f11gka different. ingersollrand25cfm175psi11hpaircompressormodel2475f11gka A digitally controlled magnetic-bearing system, consisting of both permanent magnets and electromagnets, replaces conventional lubricated bearings. The frictionless compressor shaft is the compressor''s only moving component. It rotates on a levitated magnetic cushion (Figure 1). Magnetic bearings--two ingersollrand25cfm175psi11hpaircompressormodel2475f11gka radial and one axial--hold the shaft in position (Figure 2). With the integration of the motor, VSD, and magnetic-bearing system, the capacitors required for the motor and drive can be used as a backup power source for the bearings in the event of a power outage or emergency shutdown.CAPACITY AND EFFICIENCYAmong the key parameters affecting performance are capacity (tons) and efficiency (kilowatts per ton). The compressor''s capacity ranges from 60 to 90 tons, depending on the operating conditions. Plans call for that range to be extended to 150 tons water-cooled and 115 tons air-cooled by the end ingersollrand25cfm175psi11hpaircompressormodel2475f11gka of 2004 with the use of R-134a refrigerant. An R-22 version is planned for retrofit applications.Efficiency improvements stem from a combination of the centrifugal compressor, permanent-magnet motor, and magnetic bearings. Within the compressor, efficiency is affected by the compressor isentropic efficiency (the efficiency of the wheels), the motor, and the bearings. Traditional induction motors of this size typically are in the 92-percent efficiency range. This compressor''s permanent-magnet motor has an efficiency of 96 to 97 percent. Efficiency is further enhanced with the use of magnetic bearings, which avoid fire friction of rubbing parts associated with traditional oiled bearings. Conventional bearings can use as much as 10,000 w, while magnetic bearings require only 180 w. That amounts to 500 times less friction loss. Current development projects are expanding the range and duty of the compressor ingersollrand25cfm175psi11hpaircompressormodel2475f11gka wheels and promise to offer even greater efficiency for water-cooled and air-cooled duties and different capacities.CONTROLSThe new compressor effectively is a computer. It provides diagnostic and performance information through Modbus to the refrigeration system, which then communicates to the building automation system through Modbus, LonWorks, or BACnet.CHILLER APPLICATIONThe compressor manufacturer and a major chiller manufacturer ingersollrand25cfm175psi11hpaircompressormodel2475f11gka teamed up to develop a line of ARI-certified water-cooled chillers, which were ingersollrand25cfm175psi11hpaircompressormodel2475f11gka expected to be introduced in January 2004. The combination of flooded-evaporator technology and an oil-free system has allowed very close approaches and, subsequently, enhanced performance. The integrated VFD allows excellent part-load performance as power consumption drops off, depending on the head relief, near the cube root of the shaft speed. Buy a gas air compressor with us and save a TON of cash. Our selection of cheap gas air compressors is second to none.
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